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Stock-Based Compensation - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified | 12 Months Ended | 1 Months Ended | 12 Months Ended |  |  | 12 Months Ended |  | 12 Months Ended
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Dec. 31, 2012 | Dec. 31, 2010 | 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] | Dec. 31, 2012 Stock option plan 2009 [Member] | Dec. 31, 2011 Stock option plan 2009 [Member] | Dec. 31, 2012 Stock option plan 1987 [Member] | Dec. 31, 2012 1987 Stock Option Plan granted prior to December 2003 [Member]
Schedule Of Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Activity [Line Items] |  |  |  |  |  |  |  |  |  |
Maximum number of shares, issued under the option plan |  |  |  |  |  |  | 16,000,000 |  |  |
Number of shares available to be granted |  |  |  |  |  |  | 8,457,666 | 9,770,666 |  |
Period of granted option |  |  |  |  |  |  | 7 years |  | 7 years | 10 years
Option vested under stock option plan to employees and consultants |  |  |  |  |  |  | One-third on each of the first three anniversaries of the date of grant |  |  |
Exercised number of shares, under stock option plan |  |  | 1,083,333 | 900,001 |  |  |  |  |  |
Cash payments made on cashless exercise of stock options |  |  | $ 25 | $ 15 | $ 4 | $ 5 |  |  |  |
Holding period of restricted stock available to executive | 4 years |  |  |  |  |  |  |  |  |
Share based compensation arrangement long-term retention program restricted stock available to executive releasing period | 10 years |  |  |  |  |  |  |  |  |
Number of days considered for weighted average trading price | 20 days |  |  |  |  |  |  |  |  |
Percentage of annual retainers | 60.00% |  |  |  |  |  |  |  |  |
Percentage of additional annual retainers | 100.00% |  |  |  |  |  |  |  |  |
Percentage of increments | 25.00% |  |  |  |  |  |  |  |  |
One-time compensation expense |  | $ 20 |  |  |  |  |  |  |  |

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- Definition The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph A240 -Subparagraph a -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. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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