Equity impact of the value of stock that has been repurchased during the period and has not been retired and is not held in treasury. Some state laws may mandate the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 29, 30, 31

-Article 5

Name:	us-gaap_StockRepurchasedDuringPeriodValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Subsequent Event - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended			6 Months Ended	1 Months Ended
	Jan. 28, 2013	Aug. 02, 2013 Subsequent Event [Member]	Jul. 16, 2013 Subsequent Event [Member]	Jul. 16, 2013 Subsequent Event [Member]	Aug. 02, 2013 Subsequent Event [Member] Dutch auction [Member]
Subsequent Event [Line Items]
Increase in stock repurchase program			$ 85
Authorized stock repurchase value	25			220
Utilized amount of stock repurchase program		120
Amount available for future purchases under the program					$ 100