Disclosure about Fair Value of Financial Instruments (Details) - USD ($)	Jun. 30, 2015		Dec. 31, 2014	Jun. 30, 2014	Dec. 31, 2013
Financial Assets:
Loans receivable, Carrying Amount	$ 760,543,000		$ 380,169,000
Available-for-sale equity investments, Carrying Amount	43,326,000		0
Available-for-sale equity investments, Fair Value	43,326,000	[1]	0
Cash and cash equivalents, Carrying Amount	217,942,000		473,726,000	$ 207,354,000	$ 158,780,000
Cash and cash equivalents, Fair Value	217,942,000		473,726,000
Foreign currency forward contract, asset	35,377,000		57,087,000
Financial Liabilities:
Borrowings under primary unsecured credit facilities, Carrying Value	350,000,000	[2]	0	$ 0
Borrowings under primary unsecured credit facilities, Fair Value	350,000,000		0
Senior unsecured notes, Carrying Amount	8,060,493,000		7,766,251,000
Senior unsecured notes, Fair Value	8,639,898,000		8,613,702,000
Secured debt, Carrying Amount	3,066,633,000		2,977,713,000
Secured debt, Fair Value	3,117,499,000		3,053,067,000
Foreign currency forward contact, liability	16,465,000		1,495,000
Redeemable OP unitholder interests	114,886,000		46,722,000
Mortgage Loans on Real Estate [Member]
Financial Assets:
Loans receivable, Carrying Amount	564,056,000		188,651,000
Loans receivable, Fair value	592,280,000		194,935,000
Other Real Estate Loans Receivable [Member]
Financial Assets:
Loans receivable, Carrying Amount	196,487,000		191,518,000
Loans receivable, Fair value	$ 196,793,000		$ 195,375,000

[1] (1) Unrealized gains or losses on equity investments are recorded in accumulated other comprehensive income (loss) at each measurement date.

[2] (1) As of June 30, 2015, letters of credit in the aggregate amount of $61,882,247 have been issued, which reduces the borrowing capacity on the unsecured revolving credit facility.