Stock-Based Compensation - Summary of restricted stock unit activity (Details) - Restricted stock units - shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Performance and Incentive Pay
Non-vested at beginning of year (in shares)	2,870,000	2,509,000
Granted (in shares)	4,804,000	0
Canceled/forfeited (in shares)	(158,000)	(1,339,000)
Vested (in shares)	(581,000)	(583,000)
Non-vested at end of year (in shares)	6,935,000	587,000