Debt (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
ODAST II Agreement | Secured Debt
Debt Instrument [Line Items]
Weighted Average Interest Rate at March 31, 2017	4.70%
Funding Debt	$ 250,000	$ 250,000
ODART Agreement | Revolving Credit Facility
Debt Instrument [Line Items]
Weighted Average Interest Rate at March 31, 2017	3.50%
Funding Debt	$ 162,353	133,767
RAOD Agreement | Revolving Credit Facility
Debt Instrument [Line Items]
Weighted Average Interest Rate at March 31, 2017	3.90%
Funding Debt	$ 99,985	99,985
ODAF I Agreement | Revolving Credit Facility
Debt Instrument [Line Items]
Weighted Average Interest Rate at March 31, 2017	8.00%
Funding Debt	$ 112,500	100,000
ODAC Agreement | Revolving Credit Facility
Debt Instrument [Line Items]
Weighted Average Interest Rate at March 31, 2017	10.20%
Funding Debt	$ 68,252	65,486
PORT II Agreement | Revolving Credit Facility
Debt Instrument [Line Items]
Weighted Average Interest Rate at March 31, 2017	3.70%
Funding Debt	$ 74,664	52,397
Other Agreements | Revolving Credit Facility
Debt Instrument [Line Items]
Total	27,864	30,887
Funding debt
Debt Instrument [Line Items]
Funding Debt	795,618	732,522
Deferred Debt Issuance Cost	(7,579)	(5,883)
Total	788,039	726,639
Corporate debt
Debt Instrument [Line Items]
Total	$ 27,971	27,966
Corporate debt | Revolving Credit Facility
Debt Instrument [Line Items]
Weighted Average Interest Rate at March 31, 2017	5.30%
Funding Debt	$ 28,000	28,000
Deferred Debt Issuance Cost	$ (29)	$ (34)