Summary of Financial Performance Thresholds and Vesting Rates (Detail) - Restricted Stock Units (RSUs) |
12 Months Ended | ||
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Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Threshold IRR | 7.00% | 7.00% | 6.00% |
| Target IRR | 9.50% | 9.50% | 8.00% |
| Maximum IRR | 13.00% | 13.00% | 10.00% |
| Threshold IRR | |||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Percentage of Shares Vesting | 33.30% | ||
| Targeted IRR | |||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Percentage of Shares Vesting | 66.60% | ||
| Maximum IRR | |||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Percentage of Shares Vesting | 100.00% | ||
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- Definition Percentage of IRR, which is the maximum. No definition available.
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- Definition Percentage of IRR, which is the target. No definition available.
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- Definition Percentage of IRR, which is the threshold. No definition available.
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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 Percentage of vesting of share-based compensation awards. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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