Fair Value Measurements - Narrative (Details) $ in Millions |
3 Months Ended | |
|---|---|---|
|
Mar. 31, 2018
USD ($)
|
Sep. 30, 2017
ft²
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||
| Restructuring charges, sublease | $ | $ 0.5 | |
| Massachusetts | ||
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||
| Area of real estate property | 108,743 | |
| Massachusetts | Property Subject to Operating Lease | ||
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||
| Area of real estate property | 25,812 |