Equity Incentive Plans and Stock-Based Compensation (Details 4) - Nonvested equity stock and stock units - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Nonvested equity stock and stock units
Nonvested at the beginning of the period (in shares)	5,289,483	4,859,135	5,861,349
Granted (in shares)	1,986,117	4,233,701	2,978,558
Vested (in shares)	(1,693,659)	(1,896,283)	(1,713,930)
Forfeited (in shares)	(730,676)	(1,907,070)	(2,266,842)
Nonvested at the end of the period (in shares)	4,851,265	5,289,483	4,859,135
Weighted-Average Grant-Date Fair Value
Nonvested at the beginning of the period (in dollars per share)	$ 11.27	$ 12.71	$ 12.68
Nonvested at the end of the period (in dollars per share)	12.82	11.27	12.71
Granted (in dollars per share)	15.60	10.17	12.77
Vested (in dollars per share)	11.70	12.40	12.39
Forfeited (in dollars per share)	$ 11.83	$ 11.33	$ 12.97