Earnings Per Share (Computation of Basic and Diluted) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Numerator:
Net income	$ 16,065	$ 12,546	$ 36,370	$ 39,742
Denominator:
Weighted-average shares outstanding - basic (shares)	17,996,000	18,430,000	17,990,000	18,511,000
Effect of dilutive shares (shares)	187,000	220,000	227,000	374,000
Weighted-average shares outstanding - diluted (shares)	18,183,000	18,650,000	18,217,000	18,885,000
Basic earnings per share (in dollars per share)	$ 0.89	$ 0.68	$ 2.02	$ 2.15
Diluted earnings per share (in dollars per share)	$ 0.88	$ 0.67	$ 2.00	$ 2.10
Anti-dilutive shares excluded (shares)	13,500	14,000