SENIOR NOTES PAYABLE AND OTHER DEBT - Summary of Senior Notes Payables and Other Debt (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Feb. 28, 2019	Jan. 03, 2019	Dec. 31, 2018
Debt instruments
Senior notes payable and other debt, gross	$ 10,789,178
Long-term debt and short-term borrowings, gross	10,789,178			$ 10,829,702
Deferred financing costs, net	(83,117)			(69,615)
Unamortized fair value adjustment	9,584			(1,163)
Unamortized discounts	(25,469)			(25,225)
Senior notes payable and other debt	10,690,176			10,733,699
Unsecured revolving credit facility (1) | Revolving Credit Facility
Debt instruments
Senior notes payable and other debt, gross	52,135			765,919
Unsecured revolving credit facility (1) | Revolving Credit Facility | Borrowings Originally Denominated in CAD
Debt instruments
Senior notes payable and other debt, gross	24,000			23,100
Unsecured revolving credit facility (1) | Revolving Credit Facility | Borrowings Originally Denominated in GBP
Debt instruments
Senior notes payable and other debt, gross	28,200			27,800
Secured revolving construction credit facility due 2022 | Revolving Credit Facility
Debt instruments
Senior notes payable and other debt, gross	104,629			90,488
3.00% Senior Notes, Series A due 2019
Debt instruments
Senior notes payable and other debt, gross	$ 299,760			293,319
Interest rate	3.00%
2.70% Senior Notes due 2020
Debt instruments
Senior notes payable and other debt, gross	$ 500,000			500,000
Interest rate	2.70%
4.25% Senior Notes due 2022
Debt instruments
Senior notes payable and other debt, gross	$ 600,000			600,000
Interest rate	4.25%
3.25% Senior Notes due 2022
Debt instruments
Senior notes payable and other debt, gross	$ 500,000			500,000
Interest rate	3.25%
3.30% Senior Notes, Series C due 2022
Debt instruments
Senior notes payable and other debt, gross	$ 187,350			183,325
Interest rate	3.30%
Unsecured Term Loan due 2023
Debt instruments
Senior notes payable and other debt, gross	$ 300,000			300,000
3.125% Senior Notes due 2023
Debt instruments
Senior notes payable and other debt, gross	$ 400,000			400,000
Interest rate	3.125%
3.10% Senior Notes due 2023
Debt instruments
Senior notes payable and other debt, gross	$ 400,000			400,000
Interest rate	3.10%
2.55% Senior Notes, Series D due 2023
Debt instruments
Senior notes payable and other debt, gross	$ 206,085			201,657
Interest rate	2.55%
Unsecured Term Loan due 2024
Debt instruments
Senior notes payable and other debt, gross	$ 600,000			600,000
3.50% Senior Notes due 2024
Debt instruments
Senior notes payable and other debt, gross	$ 400,000	$ 400,000		0
Interest rate	3.50%	3.50%
3.75% Senior Notes due 2024
Debt instruments
Senior notes payable and other debt, gross	$ 400,000			400,000
Interest rate	3.75%
4.125% Senior Notes, Series B due 2024
Debt instruments
Senior notes payable and other debt, gross	$ 187,350			183,324
Interest rate	4.125%
3.50% Senior Notes due 2025
Debt instruments
Senior notes payable and other debt, gross	$ 600,000			600,000
Interest rate	3.50%
4.125% Senior Notes due 2026
Debt instruments
Senior notes payable and other debt, gross	$ 500,000			500,000
Interest rate	4.125%
3.25% Senior Notes due 2026
Debt instruments
Senior notes payable and other debt, gross	$ 450,000			450,000
Interest rate	3.25%
3.85% Senior Notes Due 2027
Debt instruments
Senior notes payable and other debt, gross	$ 400,000			400,000
Interest rate	3.85%
4.00% Senior Notes due 2028
Debt instruments
Senior notes payable and other debt, gross	$ 650,000			650,000
Interest rate	4.00%
4.40% Senior Notes due 2029
Debt instruments
Senior notes payable and other debt, gross	$ 750,000			750,000
Interest rate	4.40%
6.90% Senior Notes due 2037
Debt instruments
Senior notes payable and other debt, gross	$ 52,400			52,400
Interest rate	6.90%
6.59% Senior Notes due 2038
Debt instruments
Senior notes payable and other debt, gross	$ 22,823			22,823
Interest rate	6.59%
5.45% Senior Notes due 2043
Debt instruments
Senior notes payable and other debt, gross	$ 0			$ 258,750
Interest rate			5.45%	5.45%
5.70% Senior Notes due 2043
Debt instruments
Senior notes payable and other debt, gross	$ 300,000			$ 300,000
Interest rate	5.70%
4.375% Senior Notes due 2045
Debt instruments
Senior notes payable and other debt, gross	$ 300,000			300,000
Interest rate	4.375%
4.875% Senior Notes due 2049
Debt instruments
Senior notes payable and other debt, gross	$ 300,000	$ 300,000		0
Interest rate	4.875%	4.875%
Mortgages Loans and Other
Debt instruments
Senior notes payable and other debt, gross	$ 1,131,646			$ 1,127,697