Shareholders' Equity (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended		1 Months Ended		12 Months Ended	2 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Mar. 31, 2014	Mar. 31, 2012	Dec. 31, 2014	Feb. 28, 2015
Common Share Issuances
Net proceeds from sale of common shares	$ 655,211
Series D
Common Share Issuances
Common stock, shares issued (in shares)		11,600,000
RMR
Common Share Issuances
Common shares issued for services rendered by RMR			102,536	33,132	119,664
RMR | Common Shares
Common Share Issuances
Common shares issued for services rendered by RMR			102,536		119,664
RMR | Common Shares | Subsequent event
Common Share Issuances
Common shares issued for services rendered by RMR						21,363