Earnings Per Share (EPS Components) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Summary of earnings per share
Net income	$ 35,225	$ 27,555
Weighted Average Shares (in shares)
BASIC SHARES	28,106,184	27,486,573
EFFECT OF DILUTIVE SECURITIES	54,466	67,381
DILUTIVE SHARES	28,160,650	27,553,954
NET INCOME PER SHARE (in dollars per share)
BASIC EPS	$ 1.25	$ 1.00
EFFECT OF DILUTIVE SECURITIES	0	0
DILUTIVE EPS	$ 1.25	$ 1.00