Commitments and Contingencies - Summary of Commitments (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
Commitments and Contingencies
Investment Commitment	$ 193,708
2017 Funding	37,421
Commitments funded	81,008
Remaining commitment	112,700
Real estate properties
Commitments and Contingencies
Investment Commitment	91,468
2017 Funding	22,162
Commitments funded	38,497
Remaining commitment	52,971
Accrued incentives and earn-out liabilities
Commitments and Contingencies
Investment Commitment	19,000
Remaining commitment	19,000
Lease incentives
Commitments and Contingencies
Investment Commitment	6,090
2017 Funding	2,245
Commitments funded	2,245
Remaining commitment	3,845
Mortgage loans
Commitments and Contingencies
Investment Commitment	51,000
2017 Funding	11,913
Commitments funded	17,252
Remaining commitment	33,748
Joint venture investments
Commitments and Contingencies
Investment Commitment	25,650
2017 Funding	1,101
Commitments funded	23,014
Remaining commitment	2,636
Notes receivable
Commitments and Contingencies
Investment Commitment	500
Remaining commitment	$ 500