Summary of Significant Accounting Policies Error Correction (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Common shares of beneficial interest, $.001 par value, 283,987,000 shares authorized; 147,577,984 and 148,557,270 shares issued and outstanding as of December 31, 2015 and December 31, 2014, respectively	$ 148	$ 149	$ 147	$ 118
Additional Paid in Capital	$ 3,669,627	3,688,644	3,617,668	2,635,751
Common shares in treasury, at cost		$ 0	$ 0	$ 0
Common shares outstanding	147,577,984	148,557,270	146,596,892	118,470,867
Adjustment to prior period balance [Member] | Parent balance sheet, equity reclassification [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Common shares of beneficial interest, $.001 par value, 283,987,000 shares authorized; 147,577,984 and 148,557,270 shares issued and outstanding as of December 31, 2015 and December 31, 2014, respectively		$ (1)	$ (1)	$ (1)
Additional Paid in Capital		(51,950)	(51,950)	(51,950)
Common shares in treasury, at cost		$ 51,951	$ 51,951	$ 51,951
Common shares outstanding		(1,249,909)	(1,249,909)	(1,249,909)
Previously reported amounts [Member] | Parent balance sheet, equity reclassification [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Common shares of beneficial interest, $.001 par value, 283,987,000 shares authorized; 147,577,984 and 148,557,270 shares issued and outstanding as of December 31, 2015 and December 31, 2014, respectively		$ 150	$ 148	$ 119
Additional Paid in Capital		3,740,594	3,669,618	2,687,701
Common shares in treasury, at cost		$ (51,951)	$ (51,951)	$ (51,951)
Common shares outstanding		149,807,179	147,846,801	119,720,776