v3.8.0.1

Share-Based Payments and Other Compensation - Deferred Compensation (Details) - Non-management Director - Restricted Stock Units (RSUs) - Director Deferral Program - shares | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Deferred compensation |  |  |
Maximum percentage of qualified remuneration | 100.00% |  |
Stock units distributed as shares | 0 | 0 | 0
Stock units outstanding | 76,611 | 60,955 | 50,376

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