Earnings Per Share - Calculation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Earnings Per Share [Abstract]
Net income	$ 97,872	$ 72,469
Income attributable to unvested participating securities, basic EPS	(417)	(310)
Net income used in calculating basic EPS	$ 97,455	$ 72,159
Weighted-average vested shares	39,456	41,131
Basic EPS	$ 2.47	$ 1.75
Income attributable to unvested participating securities, diluted EPS	$ (416)	$ (310)
Net income used in calculating diluted EPS	$ 97,456	$ 72,159
Dilutive effect of incremental shares to be issued for contingently-issuable shares	125	108
Weighted-average shares used in calculating diluted EPS	39,581	41,239
Diluted EPS	$ 2.46	$ 1.75