Debt - Schedule of Debt (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Debt [Roll Forward]
Total debt, Beginning balance	$ 6,087,922
Debt Issuances, Net	1,970,371
Repayments, Extinguishment and Assumptions, Net	(2,356,459)
Accretion and Amortization, Net	3,891
Total debt, Ending balance	5,705,725
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
Debt Issuances	705
Debt Issuances, Deferred costs	(96)
Debt Issuances, Net	609
Repayments, Extinguishment and Assumptions	(388,780)
Repayments, Extinguishment and Assumptions of Debt, Premium	(1,503)
Repayments, Extinguishment and Assumptions of Debt, Deferred costs	615
Repayments, Extinguishment and Assumptions, Net	(389,668)
Accretion and Amortization	(7,713)
Accretion and Amortization, Deferred costs	2,249
Accretion and Amortization, Net	(5,464)
Outstanding balance, Ending balance	1,529,057
Net premiums (discount), Ending balance	6,861
Deferred costs, Ending balance	(7,784)
Total debt, Ending balance	1,528,134
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
Debt Issuances	600,000
Debt Issuance, Discount	(6,948)
Debt Issuances, Deferred costs	(5,011)
Debt Issuances, Net	588,041
Repayments, Extinguishment and Assumptions	(1,150,000)
Repayments, Extinguishment and Assumptions of Debt, Deferred costs	2,144
Repayments, Extinguishment and Assumptions, Net	(1,147,856)
Accretion and Amortization	644
Accretion and Amortization, Deferred costs	4,301
Accretion and Amortization, Net	4,945
Outstanding balance, Ending balance	2,850,000
Net premiums (discount), Ending balance	(10,419)
Deferred costs, Ending balance	(25,842)
Total debt, Ending balance	2,813,739
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
Repayments, Extinguishment and Assumptions	(80,698)
Repayments, Extinguishment and Assumptions of Debt, Discount	391
Repayments, Extinguishment and Assumptions of Debt, Deferred costs	372
Repayments, Extinguishment and Assumptions, Net	(79,935)
Accretion and Amortization	1,663
Accretion and Amortization, Deferred costs	1,572
Accretion and Amortization, Net	3,235
Outstanding balance, Ending balance	321,802
Net premiums (discount), Ending balance	(1,855)
Deferred costs, Ending balance	(1,764)
Total debt, Ending balance	318,183
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	1,386,000
Debt Issuances, Deferred costs	(4,279)
Debt Issuances, Net	1,381,721
Repayments, Extinguishment and Assumptions	(739,000)
Repayments, Extinguishment and Assumptions of Debt, Deferred costs	0
Repayments, Extinguishment and Assumptions, Net	(739,000)
Accretion and Amortization, Deferred costs	1,175
Accretion and Amortization, Net	1,175
Outstanding balance, Ending balance	1,050,000
Deferred costs, Ending balance	(4,331)
Total debt, Ending balance	$ 1,045,669