Financial Instruments and Fair Value Measurements (Details 1) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Debt:
Debt	$ 12,147,277	$ 6,506,029
Fair values	12,445,774	6,860,092
Credit Facilities [Member]
Debt:
Debt	1,354,323	520,141
Fair values	1,354,563	526,684
Senior notes [Member]
Debt:
Debt	4,778,782	3,195,724
Fair values	4,882,028	3,403,353
Exchangeable senior notes [Member]
Debt:
Debt	1,351,267	1,521,568
Fair values	1,435,600	1,591,976
Secured mortgage debt [Member]
Debt:
Debt	2,035,660	1,249,729
Fair values	2,166,378	1,320,084
Secured mortgage debt of consolidated investees [Member]
Debt:
Debt	1,371,885	0
Fair values	1,385,002
Other debt of consolidated investees [Member]
Debt:
Debt	859,254	0
Fair values	825,333
Other debt [Member]
Debt:
Debt	396,106	18,867
Fair values	$ 396,870	$ 17,995