Debt (Details 3) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Interest expense related to exchangeable senior notes
Coupon rate	$ 500,685	$ 435,289	$ 382,362
Amortization of discount	228	47,136	67,542
Amortization of deferred loan costs	20,476	32,402	17,069
Net interest expense	468,738	461,166	372,768
Exchangeable senior notes [Member]
Interest expense related to exchangeable senior notes
Coupon rate	24,810	37,562	55,951
Amortization of discount	32,393	48,128	71,662
Amortization of deferred loan costs	2,071	2,691	3,801
Net interest expense	$ 59,274	$ 88,381	$ 131,414
Effective interest rate	4.79%	4.90%	5.55%