Reconciliation of Segment Income from Operations to Income before Income Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Segment Reporting [Abstract]
Total segment income from operations	$ 67,651	$ 78,291	$ 125,096	$ 145,352
Interest and other debt expense	16,883	16,762	33,339	33,205
Income before income taxes	$ 50,768	$ 61,529	$ 91,757	$ 112,147