Earnings Per Share (Computation of Basic and Diluted) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Numerator:
Net income	$ 28,655	$ 14,520	$ 59,873	$ 27,779
Denominator:
Weighted-average shares outstanding - basic (in shares)	18,729,000	18,676,000	18,721,000	18,673,000
Effect of dilutive shares (in shares)	117,000	5,000	89,000	13,000
Weighted-average shares outstanding - dilutive (in shares)	18,846,000	18,681,000	18,810,000	18,686,000
Basic earnings per share (in dollars per share)	$ 1.53	$ 0.78	$ 3.20	$ 1.49
Diluted earnings per share (in dollars per share)	$ 1.52	$ 0.78	$ 3.18	$ 1.49
Anti-dilutive shares excluded (in shares)	1,769	55,961