Quarterly Financial Data (Unaudited) - Summary of Unaudited Quarterly Results of Operations (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]
Revenue	$ 157,022	$ 180,269	$ 177,466	$ 204,726	$ 146,652	$ 165,145	$ 168,296	$ 197,078	$ 719,483	$ 677,171	$ 612,689
Operating expenses	154,316	155,233	158,317	161,938	144,291	146,464	147,202	155,382	629,804	593,339	540,305
Gross margin	2,706	25,036	19,149	42,788	2,361	18,681	21,094	41,696	89,679	83,832	72,384
Corporate general and administrative	6,790	8,889	8,306	10,198	7,821	8,944	7,649	9,984	34,183	34,398	30,209
Operating income (loss)	(4,084)	16,147	10,843	32,590	(5,460)	9,737	13,445	31,712	55,496	49,434	42,175
Other (expense) income:
Interest expense	(2,991)	(3,123)	(3,577)	(3,433)	(3,358)	(3,815)	(4,145)	(4,056)	(13,124)	(15,374)	(14,999)
Gain on sale of operations, net	1,210	17	68	8	7	6	48	18	1,303	79	2,766
Other income (loss), net	2,350	(1,368)	3,936	1,975	3,203	2,371	515	1,728	6,893	7,817	8,215
Total other (expense) income, net	569	(4,474)	427	(1,450)	(148)	(1,438)	(3,582)	(2,310)	(4,928)	(7,478)	(4,018)
Income (loss) from continuing operations before income tax expense (benefit)	(3,515)	11,673	11,270	31,140	(5,608)	8,299	9,863	29,402	50,568	41,956	38,157
Income tax expense (benefit)	(2,137)	4,353	4,824	13,114	(2,698)	2,707	4,260	12,308	20,154	16,577	14,364
Income (loss) from continuing operations	(1,378)	7,320	6,446	18,026	(2,910)	5,592	5,603	17,094	30,414	25,379	23,793
(Loss) income from operations of discontinued operations, net of tax	60	(239)	(312)	(263)	(1,130)	453	1,639	1,186	(754)	2,148	7,263
(Loss) gain on disposal of discontinued operations, net of tax	(7)	607	(27)	(474)	93	56,315	1,905	23	99	58,336	90
Net income (loss)	$ (1,325)	$ 7,688	$ 6,107	$ 17,289	$ (3,947)	$ 62,360	$ 9,147	$ 18,303	$ 29,759	$ 85,863	$ 31,146
Basic:
Continuing operations	$ (0.03)	$ 0.15	$ 0.13	$ 0.37	$ (0.06)	$ 0.12	$ 0.11	$ 0.35	$ 0.63	$ 0.52	$ 0.49
Discontinued operations	$ 0.00	$ 0.01	$ 0.00	$ (0.01)	$ (0.02)	$ 1.16	$ 0.07	$ 0.02	$ (0.01)	$ 1.25	$ 0.14
Net income (loss)	$ (0.03)	$ 0.16	$ 0.13	$ 0.36	$ (0.08)	$ 1.28	$ 0.18	$ 0.37	$ 0.62	$ 1.77	$ 0.63
Diluted:
Continuing operations	$ (0.03)	$ 0.14	$ 0.12	$ 0.34	$ (0.06)	$ 0.11	$ 0.11	$ 0.34	$ 0.59	$ 0.52	$ 0.48
Discontinued operations	$ 0.00	$ 0.01	$ 0.00	$ (0.01)	$ (0.02)	$ 1.16	$ 0.07	$ 0.02	$ (0.01)	$ 1.23	$ 0.15
Net income (loss)	$ (0.03)	$ 0.15	$ 0.12	$ 0.33	$ (0.08)	$ 1.27	$ 0.18	$ 0.36	$ 0.58	$ 1.75	$ 0.63
Basic weighted average common shares	48,455	48,451	48,273	48,182	46,681	48,504	49,639	49,417	48,343	48,632	49,002
Diluted weighted average common shares	48,455	51,209	52,052	52,618	46,981	49,003	49,929	49,836	51,487	49,141	49,252