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Equity - Incentive Equity Awards - Additional Information (Detail) - USD ($) $ in Thousands |  |  |  |  |  |  |  | 1 Months Ended | 12 Months Ended
--- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Nov. 01, 2018 | May 14, 2018 | Mar. 12, 2018 | Feb. 01, 2018 | Oct. 02, 2017 | May 15, 2017 | Feb. 01, 2017 | Sep. 30, 2018 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Stockholders Equity Note [Line Items] |  |  |  |  |  |  |  |  |  |  |
Stock options, outstanding |  |  |  |  |  |  |  |  | 19,263,038 | 24,108,000 |
Shares issued, exercise of stock options |  |  |  |  |  |  |  |  | 8,138,305 | 356,656 |
Proceeds from exercise of stock options, net of transaction costs |  |  |  |  |  |  |  |  | $ 26,402 | $ 638 | $ 287
Restricted Stock Units (RSUs) |  |  |  |  |  |  |  |  |  |  |
Stockholders Equity Note [Line Items] |  |  |  |  |  |  |  |  |  |  |
Restricted stock units, outstanding |  |  |  |  |  |  |  |  | 9,633,250 |  |
Percentage of outstanding shares on a fully diluted basis |  |  |  |  |  |  |  |  | 3.00% |  |
Stock units, Granted |  |  |  |  |  |  |  |  | 2,633,000 | 4,197,000 |
Restricted Stock Units (RSUs) | Stock Incentive Plan 2011 |  |  |  |  |  |  |  |  |  |  |
Stockholders Equity Note [Line Items] |  |  |  |  |  |  |  |  |  |  |
Stock units, Granted |  | 190,034 |  | 1,305,575 |  | 91,504 | 1,575,000 |  |  |  |
Stock units, Vesting Period |  | 3 years |  | 3 years |  | 3 years | 3 years |  |  |  |
Restricted Stock Units (RSUs) | Stock Incentive Plan 2011 | Vesting Period |  |  |  |  |  |  |  |  |  |  |
Stockholders Equity Note [Line Items] |  |  |  |  |  |  |  |  |  |  |
Stock units, Granted | 90,000 |  | 970,000 |  | 220,000 | 2,310,000 |  |  |  |  |
Stock units, Vesting Period |  |  |  |  |  | 3 years |  |  |  |  |
Restricted Stock Units (RSUs) | Stock Incentive Plan 2011 | Vest over a three year period |  |  |  |  |  |  |  |  |  |  |
Stockholders Equity Note [Line Items] |  |  |  |  |  |  |  |  |  |  |
Shares issued, related to the vesting of RSUs |  |  |  |  |  |  |  |  | 506,679 |  |
Treasury shares for settlement of employee tax obligations |  |  |  |  |  |  |  |  | 183,828 |  |
Stock Options |  |  |  |  |  |  |  |  |  |  |
Stockholders Equity Note [Line Items] |  |  |  |  |  |  |  |  |  |  |
Percentage of outstanding shares on a fully diluted basis |  |  |  |  |  |  |  |  | 5.00% |  |
Stock units, Vesting Period |  |  |  |  |  |  |  |  | 4 years |  |
Stock Options | Stock Incentive Plan 2011 |  |  |  |  |  |  |  |  |  |  |
Stockholders Equity Note [Line Items] |  |  |  |  |  |  |  |  |  |  |
Stock options, Granted |  | 286,536 |  | 2,205,075 |  | 131,575 | 2,642,500 |  |  |  |
Stock units, Vesting Period |  |  |  | 4 years |  |  | 4 years |  | 4 years |  |
Performance-Based RSUs |  |  |  |  |  |  |  |  |  |  |
Stockholders Equity Note [Line Items] |  |  |  |  |  |  |  |  |  |  |
Shares issued, related to the vesting of RSUs |  |  |  |  |  |  |  | 2,499,750 |  |  |
Treasury shares for settlement of employee tax obligations |  |  |  |  |  |  |  | 764,819 |  |  |

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- Definition Amount of cash inflow from exercise of stock options granted under share-based compensation arrangement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2A -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=109197908&loc=SL79508275-113901 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3255-108585 + Details
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- Definition Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition The number of grants made 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://fasb.org/us-gaap/role/ref/legacyRef -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=109197908&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://fasb.org/us-gaap/role/ref/legacyRef -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=109197908&loc=d3e5070-113901 + Details
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