Senior Unsecured Notes and Secured Debt (Details 1) (USD $)	9 Months Ended		12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Dec. 31, 2012
Unsecured note issuances
Senior unsecured debt issued	$ 0	$ 497,862,000
Senior unsecured debt redeemed	(47,591,000)	(217,615,000)
Excluding Fair Value Adjustments [Member]
Unsecured note issuances
Senior unsecured debt balance	7,342,328,000	6,175,118,000	7,421,707,000	5,894,403,000
Senior unsecured debt issued	0	500,000,000
Senior unsecured debt redeemed	(47,660,000)	(219,285,000)
Senior unsecured debt foreign currency	$ (31,719,000)	$ 0
Senior unsecured debt balance average rate	0.04388	0.0448	0.044	0.04675
Senior unsecured debt issued average rate	0	0.01552
Senior unsecured debt redeemed average rate	0.03	0.03
Senior unsecured debt foreign currency average rate	0.03892	0