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Shared-Based Payments - Schedule of Stock Option Activity (Detail) (USD $) | 9 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Sep. 30, 2013 | Dec. 31, 2012 | Dec. 31, 2011 | Mar. 16, 2011
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract] |  |  |  |
Number of Options, Outstanding, Beginning Balance | 3,249,702 | 2,885,417 |  |
Number of Options, Granted | 687,183 | 454,014 |  |
Number of Options, Exercised | (1,025,933) | (49,883) |  |
Number of Options, Forfeited or expired | (33,949) | (39,846) |  |
Number of Options, Outstanding, Ending Balance | 2,877,003 | 3,249,702 | 2,885,417 |
Weighted- Average Exercise Price, Outstanding, Beginning Balance | $ 0.94 | $ 0.94 |  | $ 0.94
Number of Options, Exercisable | 1,855,178 | 2,620,100 |  |
Weighted- Average Exercise Price, Granted | $ 3.19 | $ 0.94 |  |
Number of Options, Vested and expected to vest | 918,600 | 2,734,949 |  |
Weighted- Average Exercise Price, Exercised | $ 0.75 | $ 0.94 |  |
Weighted- Average Exercise Price, Forfeited or expired | $ 1.13 | $ 0.94 |  |
Weighted- Average Exercise Price, Outstanding, Ending Balance | $ 1.50 | $ 0.94 | $ 0.94 | $ 0.94
Weighted- Average Exercise Price, Exercisable | $ 0.94 | $ 0.94 |  |
Weighted- Average Exercise Price, Vested and expected to vest | $ 2.44 | $ 0.94 |  |
Weighted Average Contractual Term, Granted | 7 years | 6 years 8 months 12 days |  |
Weighted Average Contractual Term, Outstanding | 7 years 2 months 12 days | 7 years 3 months 18 days | 7 years 4 months 24 days |

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- Definition The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option 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)(1)(iii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option 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)(1)(iii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option 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)(1)(iv)(3) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + 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 + Details
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- Definition Number of options outstanding, including both vested and non-vested options. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + 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 (e)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition As of the balance sheet date, the weighted-average exercise price for outstanding stock options that are fully vested or expected 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 (e)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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