Condensed Consolidated Statements of Changes in Shareholders' Equity (USD $) In Thousands, unless otherwise specified	Total USD ($)	Preferred Shares	Preferred Shares Paid-In Capital USD ($)	Common Shares	Common Shares Paid-In Capital USD ($)	Accumulated Other Comprehensive Loss USD ($)	Accumulated Deficit USD ($)
Balance at Dec. 31, 2012	$ 1,839,122				$ 2,762,584	$ (70,226)	$ (853,236)
Balance (in shares) at Dec. 31, 2012				178,437
Increase (Decrease) in Shareholders' Equity
Net income	98,336						98,336
Other comprehensive income	16,683					16,683
Distributions declared on preferred shares	(6,738)						(6,738)
Distributions declared on common shares	(53,243)						(53,243)
Grant of restricted common shares (in shares)				292
Issuance of common shares	321				321
Issuance of common shares (in shares)				30
Repurchase and cancellation of common shares	(280)				(280)
Repurchase and cancellation of common shares (in shares)				(25)
Issuance of common shares in exchange for convertible notes	186,254				186,254
Issuance of common shares in exchange for convertible notes (in shares)				26,051
Issuance of preferred shares	361,622		361,622
Issuance of preferred shares (in shares)		14,950
Share-based compensation expense related to restricted common shares	980				980
Balance at Mar. 31, 2013	$ 2,443,057		$ 361,622		$ 2,949,859	$ (53,543)	$ (814,881)
Balance (in shares) at Mar. 31, 2013		14,950		204,785