Debt (Details) - USD ($)	Feb. 14, 2017	Dec. 31, 2016	Dec. 08, 2016	Nov. 30, 2016	Nov. 29, 2016	Aug. 19, 2016	Jun. 17, 2016	Jun. 16, 2016	Feb. 26, 2016	Dec. 31, 2015	Jun. 12, 2015	May 22, 2015	Nov. 30, 2014
Debt Instrument [Line Items]
Total		$ 760,522,000
ODAST II Agreement | Secured Debt
Debt Instrument [Line Items]
Weighted Average Interest Rate at December 31, 2016		4.70%
Funding Debt		$ 250,000,000								$ 0
ODART Agreement | Revolving Credit Facility
Debt Instrument [Line Items]
Weighted Average Interest Rate at December 31, 2016		3.40%
Funding Debt		$ 133,767,000								42,090,000
Line of credit							$ 162,400,000.0	$ 150,000,000
RAOD Agreement | Revolving Credit Facility
Debt Instrument [Line Items]
Weighted Average Interest Rate at December 31, 2016		3.80%
Funding Debt		$ 99,985,000								47,465,000
Line of credit									$ 100,000,000			$ 50,000,000
ODAF Agreement | Secured Debt
Debt Instrument [Line Items]
Weighted Average Interest Rate at December 31, 2016		8.00%
Funding Debt		$ 100,000,000								0
ODAF Agreement | Revolving Credit Facility
Debt Instrument [Line Items]
Line of credit						$ 100,000,000
ODAC Agreement | Revolving Credit Facility
Debt Instrument [Line Items]
Weighted Average Interest Rate at December 31, 2016		10.00%
Funding Debt		$ 65,486,000								27,699,000
PORT II Agreement | Revolving Credit Facility
Debt Instrument [Line Items]
Weighted Average Interest Rate at December 31, 2016		3.70%
Funding Debt		$ 52,397,000								0
Line of credit			$ 200,000,000
Other Agreements | Revolving Credit Facility
Debt Instrument [Line Items]
Total		30,887,000								19,644,000
ODAST Agreement | Secured Debt
Debt Instrument [Line Items]
Funding Debt		$ 0								174,980,000
ODAP Agreement | Revolving Credit Facility
Debt Instrument [Line Items]
Weighted Average Interest Rate at December 31, 2016		5.00%
Funding Debt		$ 0								8,819,000
PORT Agreement | Revolving Credit Facility
Debt Instrument [Line Items]
Weighted Average Interest Rate at December 31, 2016		2.80%
Total		$ 0								59,415,000
Line of credit											$ 100,000,000
Funding debt
Debt Instrument [Line Items]
Funding Debt		732,522,000								380,112,000
Deferred Debt Issuance Cost		(5,883,000)								(4,222,000)
Total		726,639,000								375,890,000
Corporate debt
Debt Instrument [Line Items]
Total		$ 27,966,000								2,695,000
Corporate debt | Revolving Credit Facility
Debt Instrument [Line Items]
Weighted Average Interest Rate at December 31, 2016		5.00%
Funding Debt		$ 28,000,000								2,700,000
Deferred Debt Issuance Cost		$ (34,000)								$ (5,000)
Line of credit				$ 30,000,000	$ 20,000,000								$ 20,000,000
Subsequent Event | ODAF Agreement | Secured Debt
Debt Instrument [Line Items]
Line of credit	$ 150,000,000