Earnings Per Share - Basic and Diluted Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net Income	$ 147,488	$ 98,938	$ 84,396	$ 36,760	$ 92,589	$ 50,580	$ 54,593	$ 40,550	$ 367,582	$ 238,312	$ 210,780
Less: distributed earnings allocated to participating securities									(583)	(466)	(413)
Less: undistributed earnings allocated to participating securities									(1,748)	(1,020)	(846)
Net income attributable to common stockholders (numerator for basic earnings per share)									365,251	236,826	209,521
Add back: undistributed earnings allocated to participating securities									1,748	1,020	846
Less: undistributed earnings reallocated to participating securities									(1,704)	(992)	(833)
Numerator for diluted earnings per share under two class method									$ 365,295	$ 236,854	$ 209,534
Weighted-average common shares outstanding (in shares)									63,455,422	61,616,988	60,571,123
Denominator for diluted earnings per share under two class method (in shares)									65,441,279	63,702,666	61,830,761
Basic Earnings Per Common Share (in dollars per share)	$ 2.27	$ 1.54	$ 1.33	$ 0.58	$ 1.48	$ 0.81	$ 0.88	$ 0.66	$ 5.76	$ 3.84	$ 3.46
Diluted Earnings Per Common Share (in dollars per share)	$ 2.19	$ 1.49	$ 1.31	$ 0.56	$ 1.42	$ 0.79	$ 0.86	$ 0.64	$ 5.58	$ 3.72	$ 3.39
Share-based Payment Arrangement, Option
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Add: dilutive effect of stock options and performance share units (in shares)									1,659,265	1,737,945	984,076
Performance Shares
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Add: dilutive effect of stock options and performance share units (in shares)									326,592	347,733	275,562