Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Weighted Average Interest Rate at December 31, 2018	4.70%
Debt	$ 821,997
Total	$ 816,231	$ 692,254
ODAST II Series 2018-1 | Secured Debt
Debt Instrument [Line Items]
Weighted Average Interest Rate at December 31, 2018	3.80%
Debt	$ 225,000	0
ODAST II Series 2016-1 | Secured Debt
Debt Instrument [Line Items]
Debt	$ 0	250,000
ODART | Revolving Credit Facility
Debt Instrument [Line Items]
Weighted Average Interest Rate at December 31, 2018	5.10%
Debt	$ 117,664	102,058
RAOD | Revolving Credit Facility
Debt Instrument [Line Items]
Weighted Average Interest Rate at December 31, 2018	4.70%
Debt	$ 113,631	86,478
ODAC | Revolving Credit Facility
Debt Instrument [Line Items]
Debt	0	62,350
ODAF | Revolving Credit Facility
Debt Instrument [Line Items]
Debt	$ 0	75,000
ODAF II | Revolving Credit Facility
Debt Instrument [Line Items]
Weighted Average Interest Rate at December 31, 2018	5.30%
Debt	$ 109,568	0
PORT II | Revolving Credit Facility
Debt Instrument [Line Items]
Weighted Average Interest Rate at December 31, 2018	5.00%
Debt	$ 108,816	63,851
LAOD | Revolving Credit Facility
Debt Instrument [Line Items]
Weighted Average Interest Rate at December 31, 2018	4.30%
Debt	$ 100,000	0
Corporate Debt | Revolving Credit Facility
Debt Instrument [Line Items]
Weighted Average Interest Rate at December 31, 2018	6.80%
Debt	$ 0	8,000
Other Agreements
Debt Instrument [Line Items]
Weighted Average Interest Rate at December 31, 2018	6.00%
Debt	$ 47,318	50,706
Debt
Debt Instrument [Line Items]
Debt	821,997	698,443
Deferred debt issuance cost	(5,766)	(6,189)
Total	$ 816,231	$ 692,254