Quarterly Financial Data (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Quarterly Financial Information [Line Items]
Total revenues	$ 171,931	$ 181,828	$ 174,827	$ 181,291	$ 162,321	$ 164,045	$ 127,690	$ 135,143	$ 709,877	$ 589,199	$ 517,299
Gross Profit	61,523	56,854	42,291	52,960	41,443	44,743	40,235	51,437
Income from continuing operations	29,014	21,492	6,299	17,653	3,862	1,356	11,654	25,632
Net income available for Common Shares	$ 24,274	$ 16,009	$ 2,064	$ 12,431	$ (160)	$ (2,852)	$ 6,827	$ 18,960	$ 59,845	$ 26,346	$ 44,257
Weighted average Common Shares outstanding - Basic	41,285	41,190	41,131	41,088	40,263	38,346	32,629	30,996	41,174	35,591	30,517
Weighted average Common Shares outstanding - Diluted	45,472	45,447	45,390	45,369	45,296	43,602	37,262	35,609	45,431	40,330	35,518
Net income (loss) per Common Share outstanding-Basic	$ 0.59	$ 0.39	$ 0.05	$ 0.30	$ 0.00	$ (0.07)	$ 0.21	$ 0.61	$ 1.33	$ 0.64	$ 1.26
Net income (loss) per Common Share outstanding-Diluted	$ 0.58	$ 0.39	$ 0.05	$ 0.30	$ 0.00	$ (0.07)	$ 0.20	$ 0.61	$ 1.32	$ 0.64	$ 1.25