Fair Value Measurements (Details 4) (Fair Value, Measurements, Nonrecurring, Level 3, USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Impairment Disclosure
Impairment charges on properties	$ 31,813	$ 32,872	$ 10,679
Continuing Operations
Impairment Disclosure
Impairment charges on properties	24,550	9,910	(1,159)
Discontinued Operations
Impairment Disclosure
Impairment charges on properties	7,263	22,962	11,838
Real Estate | Continuing Operations
Impairment Disclosure
Total fair value measurements	15,495	0	380
Impairment charges on properties	4,673	0	243
Real Estate | Discontinued Operations
Impairment Disclosure
Total fair value measurements	19,413	39,642	42,207
Impairment charges on properties	6,192	12,495	11,838
Operating real estate | Discontinued Operations
Impairment Disclosure
Total fair value measurements	3,709	5,002	0
Impairment charges on properties	1,071	10,467	0
Net investments in direct financing lease | Continuing Operations
Impairment Disclosure
Total fair value measurements	891	0	0
Impairment charges on properties	68	0	(1,608)
Equity investments in real estate | Continuing Operations
Impairment Disclosure
Total fair value measurements	5,111	17,140	1,554
Impairment charges on properties	19,256	9,910	206
Marketable Securities [Member] | Marketable Securities [Member] | Continuing Operations
Impairment Disclosure
Total fair value measurements	483	0	0
Impairment charges on properties	$ 553	$ 0	$ 0