Stockholders' Equity - Changes To Equity (Details) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Increase (Decrease) in Common Shares Outstanding [Roll Forward]
Common shares outstanding at beginning of period (in shares)	161,846,525	172,121,491	177,407,622
Vesting of performance units (in shares)	296,801	592,602	115,596
Vesting of restricted stock with performance feature (in shares)	553,381	412,465	543,396
Forfeitures of restricted stock (in shares)	0	(13,807)	(58,497)
Purchase of treasury stock (in shares)	(283,047)	(11,266,226)	(5,886,626)
Common shares outstanding at end of period (in shares)	162,413,660	161,846,525	172,121,491
Shares withheld under terms of agreements (in shares)	283,047	415,466	369,255