Quarterly Financial Information (Unaudited) - Quarterly Financial Data (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
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 291,612	$ 245,015	$ 257,913	$ 246,451	$ 266,070	$ 221,196	$ 245,183	$ 222,113	$ 1,040,991	$ 954,562	$ 986,594
Depreciation and amortization	28,010	28,033	28,232	28,003	27,549	27,916	29,054	32,009	112,278	116,528	130,691
Operating income (loss)	43,739	29,083	47,486	32,797	29,726	19,803	28,903	(2,244)	153,105	76,188	(4,754)
Income (loss) before income taxes and discontinued operations	61,633	14,654	28,555	20,158	17,970	5,783	14,584	(12,522)	125,000	25,815	(28,669)
(Provision) benefit for income taxes	1,096	463	(576)	484	12,136	12,450	1,784	66,292	1,467	92,662	2,034
Income from continuing operations	62,729	15,117	27,979	20,642	30,106	18,233	16,368	53,770	126,467	118,477	(26,635)
Income (loss) from discontinued operations, net of taxes	(51)	13	12	11	56	(202)	11	10	(15)	(125)	(9)
Net income	62,678	15,130	27,991	20,653	30,162	18,031	16,379	53,780	126,452	118,352	(26,644)
Net income available to common stockholders	$ 62,213	$ 15,130	$ 23,039	$ 20,653	$ 30,162	$ 18,031	$ 11,510	$ 53,780	$ 121,035	$ 113,483	$ (26,644)
Net income per share	$ 1.22	$ 0.30	$ 0.45	$ 0.41	$ 0.60	$ 0.36	$ 0.22	$ 1.03	$ 2.38	$ 2.22	$ (0.56)
Net income per share - assuming dilution	$ 1.21	$ 0.25	$ 0.38	$ 0.32	$ 0.48	$ 0.30	$ 0.18	$ 0.81	$ 2.17	$ 1.81	$ (0.56)