Description of the Business and Basis of Presentation - Schedule of Impact of Corrections on Affected Condensed Consolidated Statement of Cash Flows Line Items (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended		12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Selected Statements of Cash Flows Data:
Net cash provided by operating activities	$ 269,939	$ 272,984	$ 286,461	$ 299,440	$ 263,923
Net cash provided by financing activities	(146,506)	17,660	(48,919)	(116,110)	(95,641)
As Previously Reported [Member]
Selected Statements of Cash Flows Data:
Net cash provided by operating activities		276,317	289,794	303,513	268,249
Net cash provided by financing activities		14,327	(52,252)	(120,183)	(99,967)
Adjustments [Member]
Selected Statements of Cash Flows Data:
Net cash provided by operating activities		(3,333)	(3,333)	(4,073)	(4,326)
Net cash provided by financing activities		$ 3,333	$ 3,333	$ 4,073	$ 4,326