Senior Unsecured Notes and Secured Debt (Details 1)	6 Months Ended		12 Months Ended
	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Unsecured note issuances
Senior unsecured debt issued	$ 743,407,000	$ 0
Senior unsecured debt redeemed	(477,550,000)	(1,000)
Excluding Fair Value Adjustments [Member]
Unsecured note issuances
Senior unsecured debt balance	8,109,461,739	7,450,107,000	$ 7,817,154,000	$ 7,421,707,000
Senior unsecured debt issued	750,000,000	0
Senior unsecured debt extinguished	(300,000,000)
Senior unsecured debt redeemed	(158,990,000)	(1,000)
Senior unsecured debt foreign currency	$ 1,297,739	$ 28,401,000
Senior unsecured debt balance average rate	0.04252	0.04402	0.04385	0.044
Senior unsecured debt issued average rate	0.04	0
Senior unsecured debt extinguished average rate	0.062	0
Senior unsecured debt redeemed average rate	0.03	0.03
Senior unsecured debt foreign currency average rate	0.03601	0.04865