Senior Unsecured Notes and Secured Debt (Details 2) (USD $)	3 Months Ended
	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
Secured debt principal activity
Secured debt issued	$ 82,724,000		$ 10,690,000
Secured debt extinguished	208,057,000		129,539,000
Excluding Fair Value Adjustments [Member]
Secured debt principal activity
Secured debt principal balance	2,972,657,000	2,941,765,000	2,875,957,000	3,010,711,000
Secured debt transferred	0
Secured debt issued	82,724,000		10,690,000
Secured debt assumed	205,897,000		0
Secured debt extinguished	(192,427,000)		(114,084,000)
Secured debt principal payments	(15,630,000)		(15,455,000)
Secured debt foreign currency	$ (49,672,000)		$ (15,905,000)
Secured debt principal balance average rate	0.0488	0.0494	0.0508	0.051
Secured debt principal transferred average rate	0		0
Secured debt principal issued average rate	0.0234		0.0354
Secured debt principal assumed average rate	0.0398		0
Secured debt principal extinguished average rate	0.0402		0.0573
Secured debt principal payment average rate	0.0501		0.0512
Secured debt principal foreign currency average rate	0.0396		0.0386