Earnings Per Share (Computation of Basic and Diluted) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Numerator:
Net income	$ 27,032	$ 14,928
Denominator:
Weighted-average shares outstanding - basic (shares)	18,056,000	17,966,000
Effect of dilutive shares (shares)	317,000	248,000
Weighted-average shares outstanding - diluted (shares)	18,373,000	18,214,000
Basic earnings per share (in dollars per share)	$ 1.50	$ 0.83
Diluted earnings per share (in dollars per share)	$ 1.47	$ 0.82
Anti-dilutive shares excluded (shares)	0	51,275