Fair Value Measurements - Notes (Details) - Notes $ in Thousands	Jun. 30, 2017 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
2033 Senior Notes	$ 29,804
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
2033 Senior Notes	29,804
Carrying Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
2033 Senior Notes	$ 28,036