Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Aug. 20, 2018
Earnings Per Common Share [Line Items]
Conversion price (in dollars per share)	$ 101.38
Numerator — basic and diluted
Net income	$ 56,747	$ 62,645
Denominator
Weighted average number of common shares outstanding — basic (in shares)	36,415	36,981
Effect of dilutive convertible notes (in shares)	433	0
Effect of dilutive stock options (in shares)	461	431
Effect of dilutive restricted shares (in shares)	881	807
Weighted average number of common shares outstanding — diluted (in shares)	38,190	38,219
Earnings per common share — basic (in dollars per share)	$ 1.56	$ 1.69
Earnings per common share — diluted (in dollars per share)	$ 1.49	$ 1.64
Stock Options And Restricted Shares
Denominator
Antidilutive stock options and restricted shares (in shares)	12	49
Senior Notes | Convertible Note Due 2023
Earnings Per Common Share [Line Items]
Interest rate (as a percent)	2.00%
Conversion price (in dollars per share)			$ 101.38