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Stock-Based Compensation - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified | 12 Months Ended |  | 12 Months Ended |  |  | 12 Months Ended
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Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2010 | Dec. 31, 2012 Stock Options | Dec. 31, 2012 Restricted Stock Units (RSUs) Installment | Dec. 31, 2011 Restricted Stock Units (RSUs) | Dec. 31, 2010 Restricted Stock Units (RSUs) | Dec. 31, 2012 Employee Stock Purchase Plan | Dec. 31, 2011 Employee Stock Purchase Plan | Dec. 31, 2010 Employee Stock Purchase Plan | Jun. 06, 2012 Employee Stock Purchase Plan | Dec. 31, 2012 Employee Stock Purchase Plan Maximum | Dec. 31, 2012 2008 Equity Incentive Plan | Jun. 06, 2012 2008 Equity Incentive Plan | Jun. 01, 2011 2008 Equity Incentive Plan | Dec. 31, 2012 2008 Equity Incentive Plan Stock Options | Dec. 31, 2012 2008 Equity Incentive Plan Performance-based Stock or Cash Awards | Dec. 31, 2011 2008 Equity Incentive Plan Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Employee Stock Purchase Plan, offering period |  |  |  |  |  |  |  |  |  |  |  | 27 months |  |  |  |  |  |
Employee Stock Purchase Plan, period for eligible employees to purchase |  |  |  |  |  |  |  |  |  |  |  | 6 months |  |  |  |  |  |
Employee Stock Purchase Plan, purchase price of common stock as percentage of fair market value |  |  |  |  |  |  |  | 85.00% |  |  |  |  | 100.00% |  |  |  |  |
Employee Stock Purchase Plan, authorized shares for issuance |  |  |  |  |  |  |  |  | 820,500 |  |  |  |  |  |  |  | 500,000 |
Increase in shares of common stock authorized for issuance |  |  |  |  |  |  |  |  |  |  | 500,000 |  |  | 3,000,000 | 2,000,000 |  |  |
Maximum number of shares of common stock authorized for issuance |  |  |  |  |  |  |  |  |  |  | 1,320,500 |  |  | 13,540,940 |  |  |  |
Number of shares available for future issuance |  |  |  |  |  |  |  | 581,879 |  |  |  |  | 4,300,000 |  |  |  |  |
Stock-based compensation, award term |  |  |  |  |  |  |  |  |  |  |  |  | 10 years |  |  |  |  |
Stock-based compensation, vesting period |  |  |  |  | 3 years |  |  |  |  |  |  |  |  |  |  | 4 years |  |
Stock option plan granted on cash award |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 1.0 |
Performance-based stock options, outstanding |  |  |  |  |  |  |  |  |  |  |  |  | 50,000 |  |  |  |  |
Stock-based compensation, shares granted |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 50,000
Aggregate number of shares of common stock reserved for future issuance | 12,900,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Outstanding options and other stock based awards | 8,600,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total intrinsic value of options exercised | 0.3 | 0.2 | 0.3 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stock-based compensation, number of installments from grant date to vest |  |  |  |  | 3 |  |  |  |  |  |  |  |  |  |  |  |  |
Fair value of restricted stock units which vested during the year |  |  |  |  | 0.04 | 0.10 | 0.05 |  |  |  |  |  |  |  |  |  |  |
Stock-based compensation expense expected to be recognized |  |  |  | $ 4.3 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stock-based compensation, weighted average recognition period |  |  |  | 2 years 5 months 19 days |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stock-based compensation, expected dividend yield | 0.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Weighted average grant-date fair value of stock options granted | $ 2.13 | $ 1.37 | $ 1.94 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Weighted average grant-date fair value of awards granted |  |  |  |  | $ 3.03 |  | $ 1.85 | $ 1.43 | $ 0.68 | $ 0.90 |  |  |  |  |  |  |  |

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- Definition As of the balance sheet date, the aggregate unrecognized cost of equity-based awards made to employees under equity-based compensation awards that have yet to vest. + 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 (i) -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 h -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. + Details
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- Definition The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target 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 (c)(2)(iii)(1) -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(1) -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 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph A240 -Subparagraph b(2)(c) -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. + Details
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- Definition The total fair value of equity-based awards for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement. + 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. + Details
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- Definition The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term. + 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 (f)(2)(iii) -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 e(2)(c) -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. + Details
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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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- 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. + Details
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- Definition Net number of share options (or share units) granted during the period. + 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 (c)(1)(iv)(1) -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 b(1)(d) -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. + Details
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- Definition The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph A240 -Subparagraph c(1) -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 (d)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Purchase price of common stock expressed as a percentage of its fair market value. + References No definition available. + Details
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