Investments in Unconsolidated Ventures - Summary of Equity Method Investments (Details) $ in Thousands	Sep. 30, 2020 USD ($) investment	Dec. 31, 2019 USD ($)
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 417,464	$ 585,022
ADC investments
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 57,452	59,576
Number of investments | investment	3
ADC investments | GS
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 57,400
Number of investments | investment	2
Other investment ventures
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 360,012	$ 525,446
Number of investments | investment	8
Each investment immaterial balance (less than)	$ 189,700
Other investment ventures | GS
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 245,900
Number of investments | investment	5