Earnings Per Share (Computation of Basic and Diluted) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Numerator:
Net income	$ 25,129	$ 7,006	$ 85,002	$ 34,785
Denominator:
Weighted-average shares outstanding - basic (in shares)	18,740,000	18,688,000	18,727,000	18,678,000
Effect of dilutive shares (in shares)	134,000	25,000	104,000	17,000
Weighted-average shares outstanding - dilutive (in shares)	18,874,000	18,713,000	18,831,000	18,695,000
Basic earnings per share (in dollars per share)	$ 1.34	$ 0.37	$ 4.54	$ 1.86
Diluted earnings per share (in dollars per share)	$ 1.33	$ 0.37	$ 4.51	$ 1.86
Anti-dilutive shares excluded (in shares)	1,994	32,501