Senior Notes Payable and Other Debt - Summary of Senior Notes Payable and Other Debt (Details) $ in Thousands, $ in Millions	Dec. 31, 2020 USD ($)	Dec. 31, 2020 CAD ($)	Apr. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)	Nov. 30, 2019 CAD ($)	Aug. 31, 2019 USD ($)	Jun. 30, 2019 USD ($)	Feb. 28, 2019 USD ($)
Debt Instrument [Line Items]
Long-term debt, gross	$ 11,983,071			$ 12,245,802
Commercial Paper	0			567,450
Debt issuance costs, net	(68,343)			(79,939)
Unamortized fair value adjustment	12,618			20,056
Debt instrument, unamortized discount	(31,934)			(27,146)
Long-term Debt	11,895,412			12,158,773
Revolving Credit Facility
Debt Instrument [Line Items]
Line of credit facility, amount outstanding	39,400
Unsecured Debt | Revolving Credit Facility
Debt Instrument [Line Items]
Long-term debt, gross	39,395			120,787
Secured revolving construction credit facility due 2022
Debt Instrument [Line Items]
Long-term debt, gross				160,492
Line of credit facility, amount outstanding	154,098
Floating Rate Series F Due 2021
Debt Instrument [Line Items]
Senior Notes	235,664			231,018
Three Point Two Five Percent Senior Notes due 2022 [Member]
Debt Instrument [Line Items]
Long-term debt, gross	263,687			500,000
3.30% Senior Notes due 2022
Debt Instrument [Line Items]
Long-term debt, gross	196,386			192,515
Unsecured Term Loan Due 2023
Debt Instrument [Line Items]
Long-term debt, gross	200,000			200,000
Unsecured Debt	200,000						$ 300,000
3.125 Senior Notes [Member]
Debt Instrument [Line Items]
Long-term debt, gross	400,000			400,000
Three Point One Senior Notes Due 2023 [Member]
Debt Instrument [Line Items]
Long-term debt, gross	400,000			400,000
2.55% Senior Notes, Series D due 2023
Debt Instrument [Line Items]
Long-term debt, gross	216,025			211,767
3.50% Senior Notes due 2024 [Member]
Debt Instrument [Line Items]
Senior Notes	400,000			400,000				$ 400,000
Interest rate								3.50%
Three Point Seven Five Zero Percent Senior Notes, Due 2024 [Member]
Debt Instrument [Line Items]
Long-term debt, gross	400,000			400,000
4.125% Senior Notes, Series B due 2024
Debt Instrument [Line Items]
Long-term debt, gross	196,386			192,515
2.80% Senior Notes, Series E due 2024 [Member]
Debt Instrument [Line Items]
Senior Notes	471,328			462,036	$ 600
Interest rate					2.80%
Unsecured Term Loan due 2025 [Member]
Debt Instrument [Line Items]
Unsecured Debt	392,773	$ 500		385,030
Three Point Five Zero Zero Senior Notes, Due 2025 [Member]
Debt Instrument [Line Items]
Long-term debt, gross	600,000			600,000
2.65% Senior Notes due 2025 [Member]
Debt Instrument [Line Items]
Senior Notes	450,000			450,000			$ 450,000
Interest rate							2.65%
Four Point One Two Five Senior Notes, Due 2026 [Member]
Debt Instrument [Line Items]
Long-term debt, gross	500,000			500,000
3.25% Senior Notes due 2026
Debt Instrument [Line Items]
Long-term debt, gross	450,000			450,000
3.850 Senior Notes Due 2037 [Member]
Debt Instrument [Line Items]
Long-term debt, gross	400,000			400,000
4.00% Senior Notes due 2028
Debt Instrument [Line Items]
Long-term debt, gross	650,000			650,000
4.40% Senior Notes due 2029
Debt Instrument [Line Items]
Long-term debt, gross	750,000			750,000
3.00% Senior Notes due 2030 [Member]
Debt Instrument [Line Items]
Senior Notes	650,000			650,000		$ 650,000
Interest rate						3.00%
4.75% Senior Notes due 2030 [Member]
Debt Instrument [Line Items]
Senior Notes	500,000		$ 500,000	0
Interest rate			4.75%
Six Point Nine Zero Percent Senior Notes, Due 2037 [Member]
Debt Instrument [Line Items]
Long-term debt, gross	52,400			52,400
Six Point Five Nine Percent Senior Notes, Due 2038 [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 22,823			22,823
Interest rate	6.59%	6.59%
Five Point Seven Zero Percent Senior Notes, Due 2043 [Member]
Debt Instrument [Line Items]
Long-term debt, gross	$ 300,000			300,000
Four Point Three Seven Five Percent Senior Notes, Due 2045 [Member]
Debt Instrument [Line Items]
Long-term debt, gross	300,000			300,000
4.875% Senior Notes due 2049 [Member]
Debt Instrument [Line Items]
Senior Notes	300,000			300,000				$ 300,000
Interest rate								4.875%
Mortgage loans and other
Debt Instrument [Line Items]
Long-term debt, gross	2,092,106			1,996,969
Borrowings originally denominated in CAD | Unsecured Debt | Revolving Credit Facility
Debt Instrument [Line Items]
Long-term debt, gross	12,200			26,200
Borrowings originally denominated in GBP | Unsecured Debt | Revolving Credit Facility
Debt Instrument [Line Items]
Long-term debt, gross	$ 27,200			$ 27,600