Employee Stock Purchase Plan, Stock Options and Warrants - PSUs and RSUs Activity (Details) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Stock-Settled Performance-Based Restricted Stock Units
Stock Units
Granted (in shares)	122	0	0
Vested (in shares)		0	0
Impact of amendments (in shares)	(20)
Balance at December 31 (in shares)	102
Expected to vest at December 31, 2020	102
Weighted Average Grant Date Fair Value
Granted (in dollars per share)	$ 43.60
Impact of amendments (in dollars per share)	43.43
Balance at December 31 (in dollars per share)	43.63
Expected to vest at December 31, 2020 (in dollars per share)	$ 43.63
Restricted Stock Units
Stock Units
Granted (in shares)	34	0	0
Vested (in shares)		0	0
Balance at December 31 (in shares)	34
Expected to vest at December 31, 2020	34
Weighted Average Grant Date Fair Value
Granted (in dollars per share)	$ 42.98
Balance at December 31 (in dollars per share)	42.98
Expected to vest at December 31, 2020 (in dollars per share)	$ 42.98