Air carrier First Officer reported a severe shear during cruise. The Captain regained aircraft control and continued safely.

Narrative

While cruising in VMC weather at FL370 we encountered a severe shear without warning. Fortunately we were much lower than max altitude due to traffic above us. Our first indication was an advancing of the airspeed. Based on the speed of momentum and trend arrow; for safety; I immediately ensured the throttles were back and deployed the speed brakes while notifying the Captain. The speed was still 8 knots below Vmo. Unfortunately the shear continued and pushed us well above Vmo activating the overspeed EICAS warning. The gain appeared to be at least 25 kts. The Captain took control of the aircraft while the shear continued and pushed us about 200' high. As the speed came under control; the shear reversed pushing us down to about 200' below cruising altitude and speed decreased below target; but not anywhere near min maneuver. The Captain retracted the Speed Brakes and disengaged the Autopilot to correct back to altitude. Center noticed our altitude and queried us. I notified Center of the shear and altitude changes. The Captain smoothly returned the aircraft to altitude and airspeed and returned the automation. Then he coordinated with the flight attendants (FAs) to ensure there were no issues in the back. We gave a full description to ATC; notified Dispatch and submitted a Maintenance write up.