Other Income (Expense) - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Other Income (Expense) [Line Items]
Other-than-temporary impairment loss	$ 403	$ 0	$ 769	$ 0
Effective interest rate	4.90%		4.90%
Litigation settlement gain (loss)	$ 0	$ 0	$ 0	$ 12,548
Litigation settlement, amount received			$ 3,500
Minimum
Other Income (Expense) [Line Items]
Retained interest, effective interest rate			3.70%
Maximum
Other Income (Expense) [Line Items]
Retained interest, effective interest rate			11.70%