Earnings Per Share (EPS Components) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Summary of earnings per share
Net income	$ 20,563	$ 20,374	$ 41,288	$ 38,985
Weighted Average Shares (in shares)
BASIC SHARES	27,257,799	26,304,129	27,144,350	26,289,726
EFFECT OF DILUTIVE SECURITIES	74,497	47,885	78,757	45,679
DILUTIVE SHARES	27,332,296	26,352,014	27,223,107	26,335,405
NET INCOME PER SHARE (in dollars per share)
BASIC EPS	$ 0.75	$ 0.77	$ 1.52	$ 1.48
EFFECT OF DILUTIVE SECURITIES	0.00	0.00	0.00	0.00
DILUTIVE EPS	$ 0.75	$ 0.77	$ 1.52	$ 1.48