Reconciliation of Segment Income from Operations to Income before Income Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Segment Reporting [Abstract]
Total segment income from operations	$ 78,291	$ 86,080	$ 145,352	$ 154,090
Interest and other debt expense	16,762	18,958	33,205	39,118
Income before income taxes	$ 61,529	$ 67,122	$ 112,147	$ 114,972