v3.8.0.1
Fair Value of Financial Instruments - Changes in Level 3 Financial Instruments (Details) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Fair Value Disclosures [Abstract]        
Transfers into Level 3 $ 0 $ 0 $ 0 $ 0
Transfers out of Level 3 $ 0 $ 0 $ 0 $ 0