Equity Investment in Real Estate and the Managed REITs (Narratives) (Details) (USD $)	3 Months Ended					1 Months Ended	3 Months Ended	1 Months Ended	3 Months Ended						3 Months Ended		3 Months Ended				3 Months Ended		1 Months Ended	3 Months Ended		3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014 Real Estate Investments	Mar. 31, 2013 Real Estate Investments	Dec. 31, 2013 Real Estate Investments	Jan. 31, 2014 CPA: 16 - Global	Mar. 31, 2013 CPA: 16 - Global	Jan. 31, 2014 CPA:16 - Global operating partnership	Mar. 31, 2013 CPA:16 - Global operating partnership	Mar. 31, 2014 CPA: 17 - Global	Mar. 31, 2013 CPA: 17 - Global	Mar. 31, 2014 CPA:17 - Global operating partnership	Mar. 31, 2013 CPA:17 - Global operating partnership	Mar. 31, 2014 CPA:18 - Global Class A	Mar. 31, 2014 CPA:18 - Global operating partnership	Mar. 31, 2014 CWI	Mar. 31, 2014 CWI operating partnership	Mar. 31, 2013 Managed REITs	Mar. 31, 2014 Managed REITs	Dec. 31, 2013 Managed REITs	Mar. 31, 2014 Managed REITs	Mar. 31, 2013 Managed REITs	Jan. 31, 2014 Managed REITs CPA:16 - Global operating partnership	Mar. 31, 2013 Managed REITs CPA:16 - Global operating partnership	Mar. 31, 2014 C1000 Logestiek Vastgoed B.V. Real Estate Investments	Mar. 31, 2014 The New York Times Company Real Estate Investments
Investments in REITs
Asset management fees receivable, shares										232,160				15,328		31,463
Aggregate unamortized basis difference on equity investments			$ 5,900,000		$ 16,600,000														$ 13,000,000	$ 80,500,000
Other-than-temporary impairment charges																		9,300,000			735,000	2,684,000	700,000	2,700,000
Gain or loss on sale of investment properties	3,176,000	(931,000)																2,700,000
Mortgage debt tenants in common																									95,000,000
Pro rata share mortgage debt on tenancy in common																									14,300,000
Other Transactions
Increase in ownership percentage of equity investments																										27.00%
Distributions received from equity investment			2,300,000	4,000,000		6,400,000	6,200,000	4,800,000	3,600,000	1,000,000	600,000	4,700,000	4,300,000		100,000		900,000
Income from equity method investments	$ 14,262,000	$ 10,656,000																$ (1,700,000)			$ 782,000	$ 1,441,000