EMB190 First Officer reported an electrical failure during cruise which resulted in loss of displays; autopilot and one thrust reverser. Flight crew diverted and landed safely.

Narrative

We were cruising at FL350; All automatization on. Normal day; Clear VFR weather. Captain was pilot flying; and the First Officer (FO) was pilot monitoring. Suddenly we heard all Master Caution chime; Aural warnings for Autopilot and Autothrottle at the same time with all the EICAS caution and advisory messages (about 2 pages) populating; and all automation disconnected. We also lost displays #1 (Captain's Primary Flight Display (PFD)) and #4 (FO's Multi-function Flight Display (MFD)) and Captain side MCDU as well. Captain took flight controls (hand flying; no FMA or any automatization available) since he was already pilot flying; and told FO to read QRH for the first 'chevron marked' Caution message on the EICAS; which was AC BUS 1 OFF.QRH's first item was to start the APU if below 30000 ft.; so Captain [requested priority handling] and asked for lower altitude and a heading since we couldn't trust the FMS data at the moment. At this point the flight attendants called us that the whole cabin went dark; only emergency lights were on; and FO told them to standby while we troubleshoot.Below FL300 we started the APU but nothing changed...we didn't get any electronics back. At this point we decided to change the pilot flying to FO and pilot monitoring (reading QRH) to Captain. Initially the situation looked like electrical emergency mode (loss of all AC power; Running on battery power only) but things just didn't add up. First; we didn't have an ELEC EMERGENCY EICAS message; and if we would have lost all of the AC power; ram air turbine (RAT) would have deployed automatically. Also we would have AC ESS BUS OFF and BATT DISCHARGE caution EICAS messages etc. as well; but we didn't.Whole upper panel was dark like usual; no lights on any switches or buttons. Also pressurization looked normal. Captain ran a second 'chevron marked' EICAS message DC BUS 1 OFF; but no help. Then Captain asked the nearest airport with a long runway; which was ZZZ; and we started to get vectors there.Captain talked [to] flight attendants about the situation; gave them the nature of [problem]; time to ZZZ 15 minutes; and I told them that I would get back to them about the possible brace etc. after more trouble shooting.Right after that Captain briefed passengers on PA about the situation; including that we have to divert to ZZZ because of electrical problems we have. We couldn't talk to the company because we only had 1 radio left; and ACARS was 'No Comm' as well. FO was still flying vectors and assigned lower altitudes; and the Captain asked for delay vectors for the preparation for the landing. All had to be done on the FO side MCDU which was still working. Changed destination to ZZZ; programmed ILS XX; Frequencies; minimums and QRH Performance for the landing numbers; weather from ATC etc.Weather was perfect VFR all the time and Runway XX in ZZZ was the longest at 10500 ft; and our ILS was working. At this point the Captain called flight attendants again; telling them that we don't need to brace; Landing should be normal; and right after that the Captain made a PA for the passengers as well to make sure they are not too worried.At this point we decided that it's better for the Captain to take the responsibility for landing; and we changed the controls and after FO verified approach information we briefed the approach; and did Approach checklist. Approach and landing were normal uneventful; autobrakes work fine; only 1 thrust reverser and no nosewheel steering though. We slowed down and took the right exit from the runway to the Taxiway 1 using differential braking. We stopped and asked Fire and Rescue to check if they saw anything unusual outside. After landing EICAS had a RAT FAIL caution message as well; but I don't recall seeing that in the flight. Also RAT never deployed. We shut down both engines (APU was still running) and the Captain called Dispatch with his cellphone for more instructions from Operations; Maintenance Control; getting tow togate etc. information (many phone calls and it took about 1 hour before we got to the gate). Fire and Rescue followed us all the way to the gate just in case.Captain talked to flight attendants and passengers many times for the updates and everyone seem to be in a good mood in the cabin; and also at the gate afterwards. Captain wrote up Electrical Failure to Maintenance Logbook and local Maintenance took the plane from the crew with the APU running and failure mode still on.