Debt - Schedule of Debt (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2019 USD ($)
Debt [Roll Forward]
Total debt, Beginning balance	$ 6,087,922
Debt Issuances, Net	1,029,720
Repayments, Extinguishment and Assumptions, Net	(1,461,493)
Accretion and Amortization, Net	2,111
Total debt, Ending balance	5,658,260
Mortgages [Member]
Debt [Roll Forward]
Outstanding balance, Beginning balance	1,917,132
Net premiums (discount), Beginning balance	16,077
Deferred costs, Beginning balance	(10,552)
Total debt, Beginning balance	1,922,657
Repayments, Extinguishment and Assumptions	(174,725)
Repayments, Extinguishment and Assumptions of Debt, Deferred costs	125
Repayments, Extinguishment and Assumptions of Debt, Premium	107
Repayments, Extinguishment and Assumptions, Net	(174,493)
Accretion and Amortization	(4,020)
Accretion and Amortization, Deferred costs	1,187
Accretion and Amortization, Net	(2,833)
Outstanding balance, Ending balance	1,742,407
Net premiums (discount), Ending balance	12,164
Deferred costs, Ending balance	(9,240)
Total debt, Ending balance	1,745,331
Mortgage note in default	19,500
Corporate Bonds [Member]
Debt [Roll Forward]
Outstanding balance, Beginning balance	3,400,000
Net premiums (discount), Beginning balance	(4,115)
Deferred costs, Beginning balance	(27,276)
Total debt, Beginning balance	3,368,609
Repayments, Extinguishment and Assumptions	(750,000)
Repayments, Extinguishment and Assumptions, Net	(750,000)
Accretion and Amortization	328
Accretion and Amortization, Deferred costs	2,193
Accretion and Amortization, Net	2,521
Outstanding balance, Ending balance	2,650,000
Net premiums (discount), Ending balance	(3,787)
Deferred costs, Ending balance	(25,083)
Total debt, Ending balance	2,621,130
Convertible Debt [Member]
Debt [Roll Forward]
Outstanding balance, Beginning balance	402,500
Net premiums (discount), Beginning balance	(3,909)
Deferred costs, Beginning balance	(3,708)
Total debt, Beginning balance	394,883
Accretion and Amortization	970
Accretion and Amortization, Deferred costs	913
Accretion and Amortization, Net	1,883
Outstanding balance, Ending balance	402,500
Net premiums (discount), Ending balance	(2,939)
Deferred costs, Ending balance	(2,795)
Total debt, Ending balance	396,766
Credit Facility [Member]
Debt [Roll Forward]
Outstanding balance, Beginning balance	403,000
Deferred costs, Beginning balance	(1,227)
Total debt, Beginning balance	401,773
Debt Issuances	1,034,000
Debt Issuances, Deferred costs	(4,280)
Debt Issuances, Net	1,029,720
Repayments, Extinguishment and Assumptions	(537,000)
Repayments, Extinguishment and Assumptions, Net	(537,000)
Accretion and Amortization, Deferred costs	540
Accretion and Amortization, Net	540
Outstanding balance, Ending balance	900,000
Deferred costs, Ending balance	(4,967)
Total debt, Ending balance	$ 895,033