Noncash Investing and Financing Activities (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Supplemental Cash Flow Information [Abstract]
Accrued dividends and distributions payable	$ 54,491	$ 50,576
Additions to real estate assets accrued but not yet paid	3,965	19,162
Decrease in real estate assets	0	(22,605)
Decrease in mortgage and other indebtedness	0	68,169
Decrease in operating assets and liabilities	$ 0	$ (1,655)