Shareholders' Equity - Narrative (Details) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended	3 Months Ended								12 Months Ended	0 Months Ended	12 Months Ended	0 Months Ended
	Jan. 31, 2014	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Jul. 25, 2014	Dec. 31, 2013	May 14, 2014
Shareholders' Equity
Distributions on common stock declared (in dollars per share)	$ 0.25	$ 0.00	$ 0.00	$ 0.00	$ 0.25	$ 0.25	$ 0.25	$ 0.25	$ 0.25
Distributions paid or declared on common shares	$ 29.6
Distribution percentage to shareholders consisting of an alternative minimum tax adjustment										15.41%
Series D
Shareholders' Equity
Conversion of stock, common shares issued (in shares)										10,412,499
Conversion of stock, preferred shares outstanding (in shares)										10,264,503
Preferred shares outstanding (in shares)		4,915,497				15,180,000				4,915,497		15,180,000
Preferred shares dividend (in dollars per share)										1.625
Preferred shares, percent dividend yield										6.50%		6.50%
Initial conversion rate		0.480775								0.480775
Initial conversion price per share (in dollars per share)		$ 52.00								52.00
Additional common shares (in shares)										2,363,248
Liquidation preference (in dollars per share)		$ 25.00								25.00
Percentage of average closing market price of the entity's common stock based on which ratio for conversion of preferred shares into common shares is determined										98.00%
Purchase price as a percentage of liquidation preference										100.00%
Number of consecutive trading days for calculating the average closing sale price of common shares										5 days
Outstanding convertible shares (in shares)		4,915,497								4,915,497
Distributions on preferred stock declared (in dollars per share)											$ 0.8125
Common Stock
Shareholders' Equity
Fundamental change conversion rate, numerator (in shares)										1.0145
Outstanding convertible shares (in shares)		2,363,248								2,363,248
Series E
Shareholders' Equity
Preferred shares outstanding (in shares)		11,000,000				11,000,000				11,000,000		11,000,000
Preferred shares dividend (in dollars per share)										1.8125
Preferred shares, percent dividend yield										7.25%		7.25%
Liquidation preference (in dollars per share)		$ 25.00								25.00
Redemption price (in dollars per share)		$ 25.00								25.00
Distributions on preferred stock declared (in dollars per share)											$ 0.90625
RMR
Shareholders' Equity
Common shares issued (in shares)										90,135
Fundamental Change Conversion Right | Series D
Shareholders' Equity
Conversion of stock, preferred shares outstanding (in shares)													10,263,003
Distribution for the excess of the market value of common shares issued above carrying value of series D preferred shares redeemed													$ 16.2
Fundamental Change Conversion Right | Common Stock
Shareholders' Equity
Conversion of stock, preferred shares outstanding (in shares)													10,411,779
Period from February 15, 2014 to May 14, 2014 | Series D
Shareholders' Equity
Dividends payable (in dollars per share)											$ 0.40625
Period from February 15, 2014 to May 14, 2014 | Series E
Shareholders' Equity
Dividends payable (in dollars per share)											$ 0.453125
Period from May 15, 2014 to August 14, 2014 | Series D
Shareholders' Equity
Dividends payable (in dollars per share)											$ 0.40625
Period from May 15, 2014 to August 14, 2014 | Series E
Shareholders' Equity
Dividends payable (in dollars per share)											$ 0.453125