Computation of Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Earnings from continuing operations	$ 65,780	$ 59,066	$ 52,947
Earnings (loss) from discontinued operations, net of taxes	(2,924)	(2,386)	755
Gain (loss) on disposal of discontinued operations, net of taxes	(4,984)	420	1,323
Net earnings	$ 57,872	$ 57,100	$ 55,025
Weighted Average Number of Shares Outstanding, Basic	27,053,000	26,744,000	26,425,000
Basic earnings per share from continuing operations	$ 2.43	$ 2.21	$ 2.00
Basic earnings (loss) per share from discontinued operations	$ (0.11)	$ (0.09)	$ 0.03
Basic earnings (loss) per share from disposal of discontinued operations	$ (0.18)	$ 0.02	$ 0.05
Basic earnings per share	$ 2.14	$ 2.14	$ 2.08
Weighted average shares issuable on exercise of dilutive stock options	147,000	159,000	162,000
Weighted average shares issuable on exercise of convertible notes	577,000	240,000	35,000
Weighted Average Number of Shares Outstanding, Diluted	27,777,000	27,143,000	26,622,000
Diluted earnings per share from continuing operations	$ 2.37	$ 2.17	$ 1.99
Diluted earnings (loss) per share from discontinued operations	$ (0.11)	$ (0.09)	$ 0.03
Diluted earnings (loss) per share from disposal of discontinued operations	$ (0.18)	$ 0.02	$ 0.05
Diluted earnings per share	$ 2.08	$ 2.10	$ 2.07
Equity awards granted to employees [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	342,994	391,717	338,248
Warrant [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	3,411,539	3,404,626	3,396,841