Share Repurchase Program (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Aug. 03, 2007
Share Repurchase Program
Share Repurchase Program	$ 150,000		$ 150,000			$ 30,000
Number of common shares purchased during period under the program	158,552		301,844
Acquisition of treasury stock	$ 11,753	$ 10,392	$ 22,145	$ 0
Treasury stock shares	2,581,414		2,581,414		2,279,570
Treasury stock, at cost	$ 105,980		$ 105,980		$ 83,835