Net Income Per Common Share Computations (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended									12 Months Ended
	Dec. 31, 2015	[1]	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Abstract]
Income from continuing operations	$ 7,508		$ 4,203	$ 55,044	$ (1,558)	$ (13,807)	$ 3,531	$ 57,333	$ (700)	$ 65,197	$ 46,357	$ 55,033
Income from continuing operations allocated to participating securities										(595)	(267)	(873)
Numerator for basic income from continuing operations per common share										64,602	46,090	54,160
Net income										65,197	46,357	54,900
Net income allocated to participating securities										(595)	(267)	(870)
Numerator for basic net income per common share										64,602	46,090	54,030
Numerator for diluted income from continuing operations per common share:										65,197	46,357	55,033
Numerator for diluted income per common share										$ 65,197	$ 46,357	$ 54,900
Denominator for net income per common share:
Basic (in shares)										17,225	17,271	17,294
Plus dilutive effect of stock options and restricted stock (in shares)										121	153	248
Plus dilutive effect of participating securities (in shares)										230	165	396
Diluted (in shares)										17,576	17,589	17,938
Basic
Income from continuing operations (in dollars per share)										$ 3.75	$ 2.67	$ 3.13
Discontinued operations (in dollars per share)										0.00	0.00	(0.01)
Basic net (loss) income per common share (in dollars per share)	$ 0.44		$ 0.24	$ 3.12	$ (0.09)	$ (0.81)	$ 0.21	$ 3.23	$ (0.04)	3.75	2.67	3.12
Diluted
Income from continuing operations (in dollars per share)										3.71	2.64	3.07
Discontinued operations (in dollars per share)										0.00	0.00	(0.01)
Diluted net (loss) income per common share (in dollars per share)	$ 0.43		$ 0.24	$ 3.10	$ (0.09)	$ (0.81)	$ 0.20	$ 3.21	$ (0.04)	$ 3.71	$ 2.64	$ 3.06

[1] Refer to Note 12—Director and Employee Benefit Plans for discussion of an out of period adjustment during the fourth quarter of 2015.