Senior Unsecured Notes and Secured Debt (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Secured debt principal activity
Secured debt issued	$ 89,208,000	$ 157,418,000	$ 119,030,000
Secured debt extinguished	674,103,000	406,210,000	83,998,000
Secured Debt [Member]
Secured debt principal activity
Secured debt principal balance	3,010,711,000	2,311,586,000	2,108,384,000	1,133,715,000
Secured debt issued	89,208,000	157,418,000	116,903,000
Secured debt assumed	1,290,858,000	444,744,000	940,854,000
Secured debt extinguished	(614,375,000)	(360,403,000)	(55,317,000)
Secured debt foreign currency	(10,361,000)	187,000	0
Secured debt principal payments	$ (56,205,000)	$ (38,744,000)	$ (27,771,000)
Secured debt principal balance average rate	0.05095	0.0514	0.05285	0.05972
Secured debt principal issued average rate	0.04982	0.04212	0.05697
Secured debt principal assumed average rate	0.04159	0.05681	0.04444
Secured debt principal extinguished average rate	0.0373	0.04672	0.05949
Secured debt principal foreign currency average rate	0.04013	0.05637	0
Secured debt principal payment average rate	0.05248	0.05456	0.05845