Reconciliation of Segment Income from Operations to Income before Income Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting [Abstract]
Total segment income from operations	$ 122,407	$ 121,923	$ 247,502	$ 267,277
Interest and other debt expense	17,318	17,159	50,657	50,364
Income before income taxes	$ 105,089	$ 104,764	$ 196,845	$ 216,913