Net Income Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Net Income Per Common Share
Number of outstanding units not included in computation of Diluted EPS (in shares)	295,000	219,000
Numerator:
Net income	$ 35,900	$ 29,988
Denominator:
Basic earnings per share weighted average shares	50,286,000	50,277,000
Dilution due to stock options and restricted stock units	441,000	282,000
Diluted earnings per share weighted average shares	50,727,000	50,559,000
Basic earnings per share (in dollars per share)	$ 0.71	$ 0.60
Diluted earnings per share (in dollars per share)	$ 0.71	$ 0.59