Derivative Instruments and Hedging Activities - Fair Value of Derivative Instruments (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Dec. 31, 2012
Designated as hedging instrument [member] \| Term loan interest rate swaps [member]
Derivatives, Fair Value [Line Items]
Derivative fair value	$ 4	$ 10	$ 0
Not designated as hedging instrument [member] \| Interest rate caps [member]
Derivatives, Fair Value [Line Items]
Derivative fair value	$ 0	$ 0	$ 0

Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 50

-Paragraph 3

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=34720828&loc=SL20225862-175312

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4B

-Subparagraph (a),(c)

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5624163-113959

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 55

-Paragraph 7

-URI http://asc.fasb.org/extlink&oid=36459792&loc=SL20226000-175313

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant