Earnings Per Common Share Computations (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Earnings from continuing operations	$ 5,973	$ 19,720	$ 55,903	$ 56,524
Earnings from continuing operations allocated to participating securities	(78)	0	(729)	(926)
Numerator for basic earnings from continuing operations per common share	5,895	19,720	55,174	55,598
Net earnings	5,973	19,780	55,902	56,742
Net earnings allocated to participating securities	(78)	0	(729)	(929)
Numuerator for basic net earnings per common share	5,895	19,780	55,173	55,813
Discontinued operations, net of income taxes	0	60	(1)	218
Net earnings	$ 5,973	$ 19,780	$ 55,902	$ 56,742
Earnings Per Share, Basic and Diluted [Abstract]
Basic (in shares)	17,130	16,858	17,004	16,555
Plus dilutive effect of stock options (in shares)	220	116	236	105
Plus dilutive effect of participating securities (in shares)	225	0	225	279
Diluted (in shares)	17,575	16,974	17,465	16,939
Earnings Per Share, Basic [Abstract]
Earnings from continuing operations (per share, basic)	$ 0.34	$ 1.17	$ 3.24	$ 3.36
Discontinued operations (per share, basic)	$ 0.00	$ 0.00	$ 0.00	$ 0.01
Net earnings (per basic share)	$ 0.34	$ 1.17	$ 3.24	$ 3.37
Earnings Per Share, Diluted [Abstract]
Earnings from continuing operations (per share, diluted)	$ 0.34	$ 1.16	$ 3.20	$ 3.34
Discontinued operations (per share, diluted)	$ 0.00	$ 0.01	$ 0.00	$ 0.01
Net earnings (per share, diluted)	$ 0.34	$ 1.17	$ 3.20	$ 3.35
Number Of Shares Excluded From Computation Of Diluated Loss Per Common Share (in shares)		18		18