Senior Unsecured Notes and Secured Debt (Details 2) $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Secured debt principal activity
Secured debt issued	$ 161,799	$ 161,992
Secured debt extinguished	1,020,129	281,051
Excluding Fair Value Adjustments [Member]
Secured debt principal activity
Secured debt principal balance	2,674,689	3,421,266	$ 3,465,066	$ 3,478,207
Secured debt issued	161,799	161,992
Secured debt assumed	23,094	0
Secured debt extinguished	(987,923)	(243,314)
Secured debt principal payments	(32,206)	(37,737)
Secured debt foreign currency	$ 44,859	$ 62,118
Secured debt principal balance average rate	0.03669	0.04328	0.04094	0.0444
Secured debt principal issued average rate	0.02331	0.03051
Secured debt principal assumed average rate	0.0667	0
Secured debt principal extinguished average rate	0.0537	0.04874
Secured debt principal payment average rate	0.04378	0.04579
Secured debt principal foreign currency average rate	0.03116	0.03652