Fair Value of Financial Instruments - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Fair Value Disclosures [Abstract]
Fair value of financial guarantees	$ 4	$ 4

Fair value portion of guarantee, including, but not limited to, financial standby letter of credit, fair value guarantee, guarantee of collection of scheduled contractual cash flows from financial assets, and contracts that contingently require the guarantor to make payments or perform services.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 460

-SubTopic 10

-Section 50

-Paragraph 5

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12201-110248

Name:	us-gaap_GuaranteesFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant