Earnings per Share (Reconciliation between Basic and Diluted Earnings per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings Per Share [Abstract]
Net income for basic and diluted earnings per share	$ 28,851	$ 29,180	$ 54,561	$ 55,388
Basic weighted average shares outstanding	30,528	31,465	30,526	31,474
Dilutive effect of stock options and restricted stock awards	140	161	110	169
Diluted weighted average shares outstanding	30,668	31,626	30,636	31,643
Basic earnings per common share	$ 0.95	$ 0.93	$ 1.79	$ 1.76
Diluted earnings per common share	$ 0.94	$ 0.92	$ 1.78	$ 1.75