Quarterly report pursuant to Section 13 or 15(d)

Fair Value - Narrative (Details)

v3.8.0.1
Fair Value - Narrative (Details) - USD ($)
Mar. 31, 2018
Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets measured at fair value $ 312,665,000 $ 354,553,000
Level 3    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets measured at fair value 0 0
Liabilities measured at fair value $ 0 $ 0