Earnings Per Share (Computation of Basic and Diluted) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Numerator:
Net income	$ 14,520	$ 24,293	$ 27,779	$ 52,692
Denominator:
Weighted-average shares outstanding - basic (in shares)	18,676,000	18,568,000	18,673,000	18,562,000
Effect of dilutive shares (in shares)	5,000	162,000	13,000	149,000
Weighted-average shares outstanding - dilutive (in shares)	18,681,000	18,730,000	18,686,000	18,711,000
Basic earnings per share (in dollars per share)	$ 0.78	$ 1.31	$ 1.49	$ 2.84
Diluted earnings per share (in dollars per share)	$ 0.78	$ 1.30	$ 1.49	$ 2.82
Anti-dilutive shares excluded (in shares)	55,961	6,256