Earnings Per Share (Computation of Basic and Diluted) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Numerator:
Net income	$ 5,377	$ 13,554	$ 20,305	$ 27,197
Denominator:
Weighted-average shares outstanding - basic (shares)	18,007,000	18,627,000	17,986,000	18,551,000
Effect of dilutive shares (shares)	246,000	429,000	248,000	452,000
Weighted-average shares outstanding - diluted (shares)	18,253,000	19,056,000	18,234,000	19,003,000
Basic earnings per share (in dollars per share)	$ 0.30	$ 0.73	$ 1.13	$ 1.47
Diluted earnings per share (in dollars per share)	$ 0.29	$ 0.71	$ 1.11	$ 1.43
Anti-dilutive shares excluded (shares)	13,500	0