Equity Investments in the Managed Programs and Real Estate - Equity Method Investments Excluding the Managed Programs (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Investments in Programs
Equity investments in real estate	$ 288,444	$ 324,004
Real Estate
Investments in Programs
Equity investments in real estate	$ 236,862	194,437
Real Estate | Third Party | Kesko Senukai
Investments in Programs
Equity method investment, ownership percentage	70.00%
Equity investments in real estate	$ 44,091	46,475
Real Estate | Third Party | BPS Nevada, LLC
Investments in Programs
Equity method investment, ownership percentage	15.00%
Equity investments in real estate	$ 23,535	22,900
Real Estate | Third Party | Affiliated Entity | Johnson Self Storage
Investments in Programs
Equity method investment, ownership percentage	90.00%
Equity investments in real estate	$ 69,404	70,690
Real Estate | CPA:18 – Global | Affiliated Entity | Bank Pekao S.A.
Investments in Programs
Equity method investment, ownership percentage	50.00%
Equity investments in real estate	$ 26,173	26,388
Real Estate | CPA:18 – Global | Affiliated Entity | State Farm Mutual Automobile Insurance Co.
Investments in Programs
Equity method investment, ownership percentage	50.00%
Equity investments in real estate	$ 15,903	17,232
Real Estate | CPA:18 – Global | Affiliated Entity | Apply Sorco AS
Investments in Programs
Equity method investment, ownership percentage	49.00%
Equity investments in real estate	$ 6,536	8,040
Real Estate | CPA:18 – Global | Affiliated Entity | Fortenova Grupa d.d.
Investments in Programs
Equity method investment, ownership percentage	20.00%
Equity investments in real estate	$ 2,858	2,712
Real Estate | WLT | Affiliated Entity | WLT
Investments in Programs
Equity method investment, ownership percentage	5.00%
Equity investments in real estate	$ 48,362	$ 0