Fair Value Measurement - Additional Information (Details) - USD ($) $ in Thousands |
Sep. 30, 2017 |
Dec. 31, 2016 |
Oct. 31, 2016 |
|---|---|---|---|
| Commercial paper | Fair Value, Measurements, Recurring | |||
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |||
| Commercial paper | $ 28,538 | $ 25,610 | |
| Commercial paper | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | |||
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |||
| Commercial paper | 28,538 | 25,610 | |
| Available for sale securities | $ 5,076 | $ 11,152 | |
| 5.125% Senior Notes Due 2024 | Senior Notes | |||
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |||
| Interest rate | 5.125% |