Reconciliation of Segment Income from Operations to Income before Income Taxes (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Segment Reporting [Abstract]
Total segment income from operations	$ 86,080	$ 74,905	$ 154,090	$ 133,029
Interest and other debt expense	18,958	15,445	39,118	32,862
Income before income taxes	$ 67,122	$ 59,460	$ 114,972	$ 100,167