Earnings Per Share (EPS Components) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Summary of earnings per share
Net income	$ 23,852	$ 20,484	$ 65,140	$ 59,469
Weighted Average Shares (in shares)
BASIC SHARES	27,436,792	26,324,316	27,242,902	26,301,340
EFFECT OF DILUTIVE SECURITIES	76,307	53,072	78,043	48,354
DILUTIVE SHARES	27,513,099	26,377,388	27,320,945	26,349,694
NET INCOME PER SHARE (in dollars per share)
BASIC EPS	$ 0.87	$ 0.78	$ 2.39	$ 2.26
EFFECT OF DILUTIVE SECURITIES	0.00	0.00	(0.01)	0.00
DILUTIVE EPS	$ 0.87	$ 0.78	$ 2.38	$ 2.26