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, 2019	Mar. 31, 2018
Numerator:
Net income	$ 30,081	$ 25,086
Income allocated to participating securities	(179)	(155)
Net income available to common shareholders	$ 29,902	$ 24,931
Denominator:
Weighted average common shares outstanding – basic (in shares)	55,347	56,464
Basic earnings per share (in dollars per share)	$ 0.54	$ 0.44
Numerator:
Income allocated to participating securities	$ (179)	$ (154)
Net income available to common shareholders	$ 29,902	$ 24,932
Denominator:
Weighted average common shares outstanding – basic (in shares)	55,347	56,464
Diluted effect of stock options and PVRSUs (in shares)	310	647
Weighted average common shares outstanding – diluted (in shares)	55,657	57,111
Diluted earnings per share (in dollars per share)	$ 0.54	$ 0.44