Shareholders' Equity (Details) (USD $)	6 Months Ended		3 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010	Jun. 30, 2011 Series E Cumulative Redeemable Preferred Shares [Member]
Redeemable Preferred Shares
Preferred shares, shares issued	35,750,000		20,800,000	14,950,000
Preferred shares, dividend rate				7.25%
Net proceeds from issuance of preferred shares	$ 361,722,000	$ 0		$ 362,000,000
Issuance costs				12,000,000
Preferred shares, redemption price per share				$ 25,000,000
Aggregate liquidation value	$ 893,750,000		$ 520,000,000	$ 374,000,000

In the event of liquidation of the Company, the holders of outstanding preferred shares would have preference over the common shareholders and would receive a distribution of $25.00 per share, plus accrued and unpaid dividends.

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