Costs Associated With Restructuring Activities - Additional Information (Details) - USD ($) |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
|
| Restructuring Cost and Reserve [Line Items] | |||
| Restructuring charges | $ 0 | $ 6,341,000 | $ 7,056,000 |
| Total restructuring costs incurred to date | 20,500,000 | ||
| Expected restructuring and related costs | 0 | ||
| Restructuring | |||
| Restructuring Cost and Reserve [Line Items] | |||
| Total restructuring costs incurred to date | 13,400,000 | ||
| Leasehold Improvements and Fixtures | |||
| Restructuring Cost and Reserve [Line Items] | |||
| Total restructuring costs incurred to date | $ 3,500,000 | ||
| Other Relocation Costs | |||
| Restructuring Cost and Reserve [Line Items] | |||
| Total restructuring costs incurred to date | $ 3,600,000 | ||