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, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Segment Reporting [Abstract]
Total segment income from operations	$ 147,635	$ 135,859	$ 301,725	$ 268,888
Interest and other debt expense	19,276	16,982	58,394	49,844
Income before income taxes	$ 128,359	$ 118,877	$ 243,331	$ 219,044