Debt - Schedule of Debt (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) note_payable	Aug. 31, 2017 USD ($)	Aug. 29, 2017 USD ($)	Jun. 27, 2017 USD ($)	Dec. 30, 2016 USD ($)
Debt [Roll Forward]
Total debt, Beginning balance	$ 6,367,248
Debt Issuances, Net	924,079
Repayments, Extinguishment and Assumptions, Net	(1,226,140)
Accretion and Amortization	8,257
Total debt, Ending balance	6,073,444
Mortgage Notes Payable and Other Debt [Member]
Debt [Roll Forward]
Total debt, Beginning balance	2,671,106
Debt Issuances, Net	4,564
Repayments, Extinguishment and Assumptions, Net	(584,170)
Accretion and Amortization	(8,808)
Total debt, Ending balance	2,082,692
Mortgages [Member]
Debt [Roll Forward]
Outstanding balance, Beginning balance	2,629,949
Net premiums (discount), Beginning balance	36,751
Deferred costs, Beginning balance	(16,633)
Debt Issuances	4,652
Debt Issuances, Deferred Costs	(88)
Repayments, Extinguishment and Assumptions	(563,563)
Repayments, Extinguishment and Assumptions of Debt, Net premiums	(526)
Repayments, Extinguishment and Assumptions of Debt, Deferred costs	883
Accretion and Amortization, (Premiums) Discount	(11,573)
Accretion and Amortization, Deferred costs	2,840
Outstanding balance, Ending balance	2,071,038
Net premiums (discount), Ending balance	24,652
Deferred costs, Ending balance	(12,998)
Mortgage notes in connection with default from non-recourse loan	$ 16,200	$ 41,600	$ 20,500	$ 38,300	$ 11,600
Number of mortgage notes payable in default | note_payable	1
Other Debt [Member]
Debt [Roll Forward]
Outstanding balance, Beginning balance	$ 20,947
Net premiums (discount), Beginning balance	92
Repayments, Extinguishment and Assumptions	(20,947)
Repayments, Extinguishment and Assumptions of Debt, Net premiums	(17)
Accretion and Amortization, (Premiums) Discount	(75)
Outstanding balance, Ending balance	0
Net premiums (discount), Ending balance	0
Corporate Bonds [Member]
Debt [Roll Forward]
Outstanding balance, Beginning balance	2,250,000
Net premiums (discount), Beginning balance	(1,937)
Deferred costs, Beginning balance	(21,839)
Total debt, Beginning balance	2,226,224
Debt Issuances	600,000
Debt Issuances, Deferred Costs	(9,485)
Debt Issuances, Net	590,515
Repayments, Extinguishment and Assumptions, Net	0
Accretion and Amortization, (Premiums) Discount	705
Accretion and Amortization, Deferred costs	4,050
Accretion and Amortization	4,755
Outstanding balance, Ending balance	2,850,000
Net premiums (discount), Ending balance	(1,232)
Deferred costs, Ending balance	(27,274)
Total debt, Ending balance	2,821,494
Convertible Debt [Member]
Debt [Roll Forward]
Outstanding balance, Beginning balance	1,000,000
Net premiums (discount), Beginning balance	(12,894)
Deferred costs, Beginning balance	(13,766)
Total debt, Beginning balance	973,340
Accretion and Amortization, (Premiums) Discount	5,112
Accretion and Amortization, Deferred costs	5,806
Accretion and Amortization	10,918
Outstanding balance, Ending balance	1,000,000
Net premiums (discount), Ending balance	(7,782)
Deferred costs, Ending balance	(7,960)
Total debt, Ending balance	984,258
Credit Facility [Member]
Debt [Roll Forward]
Outstanding balance, Beginning balance	500,000
Deferred costs, Beginning balance	(3,422)
Total debt, Beginning balance	496,578
Debt Issuances	329,000
Debt Issuances, Net	329,000
Repayments, Extinguishment and Assumptions	(644,000)
Repayments, Extinguishment and Assumptions of Debt, Deferred costs	2,030
Repayments, Extinguishment and Assumptions, Net	(641,970)
Accretion and Amortization, Deferred costs	1,392
Accretion and Amortization	1,392
Outstanding balance, Ending balance	185,000
Deferred costs, Ending balance
Total debt, Ending balance	$ 185,000