Commitments and Contingencies (Details) (USD $)	12 Months Ended
	Dec. 31, 2011 Integer	Dec. 31, 2010	Dec. 31, 2009
Operating Leased Assets [Line Items]
Number of corporate office lease agreements	3
Rent expense	$ 3,700,000	$ 2,900,000	$ 3,900,000
2012	284,492,000
2013	282,889,000
2014	262,725,000
2015	253,516,000
2016	250,393,000
Thereafter	814,792,000
Total	$ 2,148,807,000
Corporate office lease A [Member]
Operating Leased Assets [Line Items]
Square footage of operating lease (in square feet)	31,845
Maturity date of office lease	2014-12-31
Corporate office lease B [Member]
Operating Leased Assets [Line Items]
Square footage of operating lease (in square feet)	73,358
Maturity date of office lease	2019-12-31
Corporate office lease C [Member]
Operating Leased Assets [Line Items]
Square footage of operating lease (in square feet)	117,609
Maturity date of office lease	2014-12-31