Earnings Per Share (Computation of Basic and Diluted) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Numerator:
Net income	$ 28,399	$ 26,136
Denominator:
Weighted-average shares outstanding - basic (shares)	18,557,000	18,288,000
Effect of dilutive shares (in shares)	135,000	322,000
Weighted-average shares outstanding - dilutive (shares)	18,692,000	18,610,000
Basic earnings per share (in dollars per share)	$ 1.53	$ 1.43
Diluted earnings per share (in dollars per share)	$ 1.52	$ 1.40
Anti-dilutive shares excluded (in shares)	23,081	0