Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Basic EPS [Abstract]
Net income	$ 112,566	$ 82,151	$ 78,409
Weighted average shares, basic (in shares)	43,701	43,575	43,244
Basic EPS (in dollars per share)	$ 2.58	$ 1.89	$ 1.81
Diluted earnings per share [Abstract]
Net income	$ 112,566	$ 82,151	$ 78,409
Dilutive effect of stock based compensation (in shares)	319	330	378
Weighted average shares, diluted (in shares)	44,020	43,905	43,622
Diluted EPS (in dollars per share)	$ 2.56	$ 1.87	$ 1.80