Other Income (Expense) - Narrative (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Income (Expense) [Line Items]
Other-than-temporary impairment losses		$ 2,288	$ 0	$ 0
Effective interest rate	4.90%	4.90%
Claim settlement		$ 0	12,548	0
Gain on sale of assets		9,800	0	0
Proceeds from settlement received		$ 3,500
Fees and expenses for the SEC investigation			$ (700)	$ 8,200
Minimum
Other Income (Expense) [Line Items]
Retained interest, effective interest rate		3.70%
Maximum
Other Income (Expense) [Line Items]
Retained interest, effective interest rate		11.80%
PCR Rentals Sale | Disposed of by Sale
Other Income (Expense) [Line Items]
Consideration received from sale of assets	$ 9,900	$ 9,900
Gain on sale of assets	$ 9,800