Senior Unsecured Notes and Secured Debt (Details 2)	3 Months Ended		6 Months Ended
	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)
Secured debt principal activity
Secured debt issued			$ 136,801,000	$ 10,690,000
Secured debt extinguished			323,950,000	219,980,000
Excluding Fair Value Adjustments [Member]
Secured debt principal activity
Secured debt principal balance	$ 2,941,765,000	$ 3,010,711,000	3,033,871,000	2,812,226,000
Secured debt transferred			0
Secured debt issued			136,801,000	10,690,000
Secured debt assumed			317,897,000	12,005,000
Secured debt extinguished			(290,984,000)	(188,722,000)
Secured debt principal payments			(32,966,000)	(1,200,000)
Secured debt foreign currency			$ (38,642,000)	$ (31,258,000)
Secured debt principal balance average rate	0.0494	0.051	0.0475	0.0504
Secured debt principal transferred average rate			0	0
Secured debt principal issued average rate			0.0284	0.0354
Secured debt principal assumed average rate			0.0322	0.0415
Secured debt principal extinguished average rate			0.0421	0.0573
Secured debt principal payment average rate			0.0477	0.0394
Secured debt principal foreign currency average rate			0.0399	0.0498