Organization, Basis of Presentation and Summary of Significant Accounting Policies - Schedule of Operating Partnership's Equity Interest (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended	6 Months Ended
	Apr. 30, 2018	Jun. 30, 2020	Jun. 30, 2020
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		$ 362.1
Unfunded Commitment		$ 0.0	$ 0.0
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		$ 440.3
Unfunded Commitment		$ 9.7	$ 9.7
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		$ 457.1
Unfunded Commitment		$ 72.9	$ 72.9
Equity interest held by Operating Partnership			23.12%
Preferred Return			6.00%
Total Distributions			$ 193.1
Fund V
Variable Interest Entity [Line Items]
Operating Partnership Share of Capital		20.10%
Capital Called		$ 213.3
Unfunded Commitment		$ 306.7	$ 306.7
Equity interest held by Operating Partnership			20.10%
Preferred Return			6.00%
Total Distributions			$ 16.7
Fund II
Variable Interest Entity [Line Items]
Total Distributions	$ 15.0