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Stock-Based Compensation - Schedule of Options Outstanding (Parenthetical) (Detail) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended					12 Months Ended		1 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Nov. 08, 2010	Aug. 19, 2010	Feb. 26, 2012 Stock Option Holder [Member]	Jul. 13, 2011 Stock Option Holder [Member]	Jun. 22, 2012 Chairman And Founder [Member]	Aug. 16, 2012 Chairman And Founder [Member]	Feb. 26, 2012 Chairman And Founder [Member]	Jul. 13, 2011 Chairman And Founder [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total intrinsic value of options exercised	$ 6	$ 19	$ 14
Stock option shares surrendered				386,666	243,000
In-the-money value of surrendered stock options				8	4
Exercised number of shares, under stock option plan						200,000	200,001	1,083,333	900,001
Cash payments made on cashless exercise of stock options								$ 25	$ 15	$ 4	$ 5

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Cashless Exercise Of Stock Options Shares

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- Definition

Cash payments made on cashless exercise of stock options.

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- Definition

In-the-money value of surrendered stock options.

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- Definition

Number of stock options surrendered for cancellation in exchange for payment of the in-the-money-value.

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- Definition

The total accumulated difference between fair values of underlying shares on dates of exercise and exercise price on options which were exercised (or share units converted) into shares during the reporting period under the plan.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (d)(2)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901



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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph c(2)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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