Equity Investments in the Managed Programs and Real Estate - Equity Method Investments Excluding the Managed Programs (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Investments in Programs
Equity investments in real estate	$ 358,068	$ 341,457
CPA: 17 - Global
Investments in Programs
Equity method investment, ownership percentage	4.377%	4.186%
Equity investments in real estate	$ 132,950	$ 125,676
Owned Real Estate
Investments in Programs
Equity investments in real estate	140,517	140,049
Owned Real Estate | Third Party | Beach House JV, LLC
Investments in Programs
Equity investments in real estate	$ 15,105	15,105
Owned Real Estate | CPA: 17 - Global | The New York Times Company
Investments in Programs
Equity method investment, ownership percentage	45.00%
Equity investments in real estate	$ 69,293	69,401
Owned Real Estate | CPA: 17 - Global | Frontier Spinning Mills, Inc.
Investments in Programs
Equity method investment, ownership percentage	40.00%
Equity investments in real estate	$ 24,167	24,153
Owned Real Estate | CPA: 17 - Global | ALSO Actebis GmbH
Investments in Programs
Equity method investment, ownership percentage	30.00%
Equity investments in real estate	$ 12,161	12,009
Owned Real Estate | CPA: 17 - Global | Jumbo Logestiek Vastgoed B.V.
Investments in Programs
Equity method investment, ownership percentage	15.00%
Equity investments in real estate	$ 10,405	10,661
Owned Real Estate | CPA: 17 - Global | Wagon Automotive GmbH
Investments in Programs
Equity method investment, ownership percentage	33.00%
Equity investments in real estate	$ 8,278	8,386
Owned Real Estate | CPA: 17 - Global | Wanbishi Archives Co. Ltd.
Investments in Programs
Equity method investment, ownership percentage	3.00%
Equity investments in real estate	$ 1,108	$ 334