Organization, Basis of Presentation and Summary of Significant Accounting Policies - Schedule of Operating Partnership's Equity Interest (Details) - USD ($) $ in Millions	1 Months Ended	9 Months Ended
	Apr. 30, 2018	Sep. 30, 2019
Operating Partnership, as General Partner or Managing Member
Variable Interest Entity [Line Items]
Total Distributions	$ 4.3
Fund II and Mervyns II
Variable Interest Entity [Line Items]
Operating Partnership Share of Capital		28.33%
Capital Called		$ 347.1
Unfunded Commitment		$ 15.0
Equity interest held by Operating Partnership		28.33%
Preferred Return		8.00%
Total Distributions		$ 146.6
Fund III
Variable Interest Entity [Line Items]
Operating Partnership Share of Capital		24.54%
Capital Called		$ 436.4
Unfunded Commitment		$ 13.6
Equity interest held by Operating Partnership		24.54%
Preferred Return		6.00%
Total Distributions		$ 568.8
Fund IV
Variable Interest Entity [Line Items]
Operating Partnership Share of Capital		23.12%
Capital Called		$ 438.1
Unfunded Commitment		$ 91.9
Equity interest held by Operating Partnership		23.12%
Preferred Return		6.00%
Total Distributions		$ 172.1
Fund V
Variable Interest Entity [Line Items]
Operating Partnership Share of Capital		20.10%
Capital Called		$ 258.6
Unfunded Commitment		$ 261.4
Equity interest held by Operating Partnership		20.10%
Preferred Return		6.00%
Total Distributions		$ 2.0
Fund II
Variable Interest Entity [Line Items]
Total Distributions	$ 15.0