Equity - Additional Information (Detail) - Restricted stock and restricted stock units [Member] - 2013 Plan [Member] $ in Millions |
12 Months Ended |
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Dec. 31, 2017
USD ($)
shares
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |
| Number of awards authorized for issuance | 4,452,597 |
| Number of awards remaining available for issuance | 1,635,094 |
| Unrecognized compensation expense | $ | $ 12 |
| Weighted-average term in which unrecognized compensation expense is expected to be recognized | 2 years |
| Employees and Directors [Member] | |
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |
| Shares awarded | 710,148 |
| Employees and Directors [Member] | Minimum [Member] | |
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |
| Restricted common shares vesting years | 2017 |
| Employees and Directors [Member] | Maximum [Member] | |
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |
| Restricted common shares vesting years | 2021 |
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- Definition Share Based Compensation Arrangement By Share Based Payment Restricted Stock Awards Vesting Date No definition available.
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- Definition Stock Based Compensation Not Yet Recognized Weighted Average Period Of Expected Recognition No definition available.
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- Definition Unrecognized cost of unvested share-based compensation awards. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available.
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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). Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Number of shares issued during the period related to Restricted Stock Awards, net of any shares forfeited. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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