Heavy Transport
Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Human-Machine Interface; Situational Awareness
Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance
Flight Crew Returned To Clearance
Environment - Non Weather Related; Human Factors
While enroute from ZZZ to ZZZ1 and approximately 10 nm west of ZZZ2; ZZZ Center called to confirm that we were level at our assigned altitude of FL370.  The autopilot and profile were engaged; but we were climbing through FL375.  We disengaged the autopilot; descended back down to FL370; and reengaged the autopilot and profile.  I think we reached ~ 750 high before descending.I did not notice the aircraft start a climb.Do not become complacent in level cruise with the autopilot engaged.
In cruise at FL370; approximately 10 NM west of ZZZ2; approaching ZZZ2; I had been cleaning the glass of all the displays; including the altitude window on the FCP. ZZZ Center asked us to 'confirm FL370;' which prompted me to look at the altimeter and I discovered were in a climb passing 37;500 feet. I disconnected the autopilot and forced the plane back down to FL370; reconnected the auto pilot; re-initiated our altitude in the FMS; and reported FL370 to ZZZ Center. Center said nothing to us again until they commanded a frequency change.In the act of cleaning the altitude window I must have rotated the altitude select dial to a higher altitude; and the airplane being in profile did what I told it to do; which was climb.Don't mess around on the FCP without monitoring the airplane flight path.
Air carrier flight crew reported that while cleaning the cockpit displays; the altitude selector was inadvertently changed resulting in an altitude deviation.