Reconciliation of Segment Income from Operations to Income before Income Taxes (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Segment Reporting [Abstract]
Total segment income from operations	$ 135,859	$ 132,432	$ 268,888	$ 266,833
Interest and other debt expense	16,982	16,005	49,844	86,326
Income before income taxes	$ 118,877	$ 116,427	$ 219,044	$ 180,507