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 [Line Items]
Total revenues	$ 190,261	$ 200,778	$ 189,025	$ 196,745	$ 180,064	$ 188,161	$ 176,915	$ 183,908	$ 776,809	$ 729,048	$ 684,298
Gross Profit	68,153	67,545	62,770	73,730	62,843	64,779	56,597	70,332
Consolidated income from continuing operations	34,262	30,276	30,040	43,890	28,713	34,936	21,786	40,470	138,468	77,247	63,747
Net income available for Common Shares	$ 29,403	$ 25,746	$ 25,483	$ 38,099	$ 24,160	$ 29,872	$ 17,860	$ 35,027	$ 138,468	$ (125,905)	$ 59,846
Weighted average Common Shares outstanding - Basic	83,562	83,531	83,234	83,116	83,003	83,021	83,021	83,026	83,362	83,018	82,348
Weighted average Common Shares outstanding - Diluted	91,644	91,528	91,420	91,353	91,334	91,259	91,128	91,060	91,511	91,196	90,862
Net income (loss) per Common Share outstanding-Basic	$ 0.35	$ 0.31	$ 0.31	$ 0.46	$ 0.29	$ 0.36	$ 0.22	$ 0.42	$ 1.42	$ 1.29	$ 0.67
Net income (loss) per Common Share outstanding-Diluted	$ 0.35	$ 0.31	$ 0.30	$ 0.46	$ 0.29	$ 0.36	$ 0.21	$ 0.42	$ 1.41	$ 1.28	$ 0.66