Financial Instruments (Details) (USD $)	6 Months Ended			6 Months Ended
	Jun. 30, 2010	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2011 Interest Rate Swaps	Jun. 30, 2010 Interest Rate Swaps	Jun. 30, 2011 Interest Rate Caps	Jun. 30, 2010 Interest Rate Caps	Jun. 30, 2011 Credit Facilities	Dec. 31, 2010 Credit Facilities	Jun. 30, 2011 Notes Payable, Other Payables [Member]	Dec. 31, 2010 Notes Payable, Other Payables [Member]	Jun. 30, 2011 Convertible Debt [Member]	Dec. 31, 2010 Convertible Debt [Member]	Jun. 30, 2011 Secured Debt [Member]	Dec. 31, 2010 Secured Debt [Member]
Derivative Activity Details [Abstract]
Notional amounts at January 1				$ 268,100	$ 157,700	$ 0	$ 0
Matured or expired contracts	(44,600)			(9,600)
Acquired Contracts				1,337,300	0	25,700
Notional amounts at June 30		1,595,800			113,100	25,700	0
Debt:
Carrying value		12,119,952,000	6,506,029,000					802,880,000	520,141,000	4,803,441,000	3,195,724,000	1,475,689,000	1,521,568,000	1,681,361,000	1,223,312,000
Derivative Activity Details [Abstract]
Notional amounts at January 1				268,100	157,700	0	0
Matured or expired contracts	(44,600)			(9,600)
Acquired Contracts				1,337,300	0	25,700
Notional amounts at June 30		$ 1,595,800			$ 113,100	$ 25,700	$ 0