Earnings Per Share - Computation Of Basic And Diluted Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Numerator:
Net income	$ 55,463	$ 30,081
Income allocated to participating securities	(317)	(179)
Net income available to common shareholders	$ 55,146	$ 29,902
Denominator:
Weighted average common shares outstanding – basic (in shares)	55,343	55,347
Basic earnings per share (in dollars per share)	$ 1.00	$ 0.54
Numerator:
Income allocated to participating securities	$ (316)	$ (179)
Net income available to common shareholders	$ 55,147	$ 29,902
Denominator:
Weighted average common shares outstanding – basic (in shares)	55,343	55,347
Diluted effect of stock options and PVRSUs (in shares)	334	310
Weighted average common shares outstanding – diluted (in shares)	55,677	55,657
Diluted earnings per share (in dollars per share)	$ 0.99	$ 0.54