Computation of Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Earnings from continuing operations	$ 58,854	$ 60,438	$ 65,780
Loss from discontinued operations, net of taxes	0	0	(2,924)
Loss on disposal of discontinued operations, net of taxes	0	0	(4,984)
Net earnings	$ 58,854	$ 60,438	$ 57,872
Basic:
Weighted average number of shares outstanding	27,107,000	27,177,000	27,053,000
Basic earnings per share from continuing operations (in dollars per share)	$ 2.17	$ 2.22	$ 2.43
Basic loss per share from discontinued operations (in dollars per share)	0.00	0.00	(0.11)
Basic loss per share from disposal of discontinued operations (in dollars per share)	0.00	0.00	(0.18)
Basic earnings per share (in dollars per share)	$ 2.17	$ 2.22	$ 2.14
Diluted:
Weighted average number of shares outstanding	27,107,000	27,177,000	27,053,000
Weighted average shares issuable on exercise of dilutive stock options	141,000	133,000	147,000
Weighted average shares issuable on exercise of convertible notes	773,000	558,000	577,000
Incremental Common Shares Attributable to Dilutive Effect of Call Options and Warrants	51,000	0	0
Weighted average number of shares outstanding, diluted	28,072,000	27,868,000	27,777,000
Diluted earnings per share from continuing operations (in dollars per share)	$ 2.10	$ 2.17	$ 2.37
Diluted loss per share from discontinued operations (in dollars per share)	0.00	0.00	(0.11)
Diluted loss per share from disposal of discontinued operations (in dollars per share)	0.00	0.00	(0.18)
Diluted earnings per share (in dollars per share)	$ 2.10	$ 2.17	$ 2.08
Equity awards granted to employees
Diluted:
Antidilutive securities excluded from computation of earnings per share	472,328	487,071	342,994
Warrant
Diluted:
Antidilutive securities excluded from computation of earnings per share	3,383,826	3,422,477	3,411,539