Net Income Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Net Income Per Common Share
Number of outstanding units not included in computation of Diluted EPS (in shares)	219,000	241,000
Numerator:
Net income	$ 29,988	$ 88,181
Denominator:
Weighted average number of common shares outstanding	50,277,000	51,440,000
Effect of outstanding share-based awards	282,000	658,000
Diluted earnings per share weighted average shares	50,559,000	52,098,000
Basic earnings per share (in dollars per share)	$ 0.60	$ 1.71
Diluted earnings per share (in dollars per share)	$ 0.59	$ 1.69