Computation of Basic and Diluted Earnings (loss) Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2014		Sep. 30, 2014		Jun. 30, 2014		Mar. 31, 2014		Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Earnings Loss Per Share [Line Items]
Continuing operations, net of tax	$ 22,699		$ (845)		$ (10,337)		$ (6,482)		$ 16,148		$ 17,146		$ (1,553)		$ (5,191)		$ 5,035		$ 26,550		$ 22,473
Discontinued operations, net of tax	0		0		0		0		0		0		0		56,782		0		56,782		(1,927)
Net income	$ 22,699		$ (845)		$ (10,337)		$ (6,482)		$ 16,148		$ 17,146		$ (1,553)		$ 51,591		$ 5,035		$ 83,332		$ 20,546
Total weighted average common stock shares outstanding																	11,301		11,300		10,995
Employee stock options																	55		1		179
Adjusted weighted average shares																	11,356		11,301		11,174
Basic earnings (loss) per share
From continuing operations	$ 2.01		$ (0.07)		$ (0.91)		$ (0.57)		$ 1.43		$ 1.52		$ (0.14)		$ (0.46)		$ 0.45		$ 2.35		$ 2.05
From discontinued operations	$ 0.00		$ 0.00		$ 0.00		$ 0.00		$ 0.00		$ 0.00		$ 0.00		$ 5.03		$ 0.00		$ 5.02		$ (0.18)
Basic earnings per share	$ 2.01	[1]	$ (0.07)	[1]	$ (0.91)	[1]	$ (0.57)	[1]	$ 1.43	[1]	$ 1.52	[1]	$ (0.14)	[1]	$ 4.57	[1]	$ 0.45	[1],[2]	$ 7.37	[1],[2]	$ 1.87	[2]
Diluted earnings (loss) per share:
From continuing operations	$ 1.99		$ (0.07)		$ (0.91)		$ (0.57)		$ 1.43		$ 1.52		$ (0.14)		$ (0.46)		$ 0.44		$ 2.35		$ 2.01
From discontinued operations	$ 0.00		$ 0.00		$ 0.00		$ 0.00		$ 0.00		$ 0.00		$ 0.00		$ 5.03		$ 0.00		$ 5.02		$ (0.17)
Diluted earnings per share	$ 1.99	[1]	$ (0.07)	[1]	$ (0.91)	[1]	$ (0.57)	[1]	$ 1.43	[1]	$ 1.52	[1]	$ (0.14)	[1]	$ 4.57	[1]	$ 0.44	[1],[2]	$ 7.37	[1],[2]	$ 1.84	[2]
Class A
Earnings Loss Per Share [Line Items]
Total weighted average common stock shares outstanding																	9,246		9,073		8,768
Class B Convertible
Earnings Loss Per Share [Line Items]
Total weighted average common stock shares outstanding																	2,055		2,227		2,227

[1] The sum of the basic and diluted earnings (loss) per share for the four quarters may differ from annual earnings (loss) per share as the weighted-average shares outstanding are computed independently for each of the quarters presented.

[2] Basic and fully diluted earnings (loss) per share for class A and class B common stock are the same.