Senior Unsecured Notes and Secured Debt (Details 1) $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Unsecured note issuances
Senior unsecured debt issued	$ 0	$ 693,560
Senior unsecured debt redeemed	0	400,000
Excluding Fair Value Adjustments [Member]
Unsecured note issuances
Senior unsecured debt balance	8,343,139	8,817,524	$ 8,260,038	$ 8,645,758
Senior unsecured debt issued	0	705,000
Senior unsecured debt extinguished	0	(400,000)
Senior unsecured debt foreign currency	$ 83,101	$ (133,234)
Senior unsecured debt balance average rate	0.04276	0.04263	0.04245	0.04237
Senior unsecured debt issued average rate	0	0.04228
Senior unsecured debt extinguished average rate	0	0.03625
Senior unsecured debt foreign currency average rate	0.0432	0.04417