Net Income per Share (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share [Abstract]
Net income	$ 25,859	$ 36,207	$ 130,704	$ 110,758
Less distributed and undistributed earnings allocated to participating securities	284	503	1,546	1,546
Net Income (Loss) Available to Common Stockholders, Basic	$ 25,575	$ 35,704	$ 129,158	$ 109,212
Weighted average common shares outstanding basic (in shares)	40,168	41,330	40,481	41,311
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	149	218	143	283
Weighted Average Number of Shares Outstanding, Diluted	40,317	41,548	40,624	41,594