Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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- Definition

Amount of assets pledged to secure a debt instrument.

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- Definition

Face (par) amount of debt instrument at time of issuance.

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- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

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- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Senior Unsecured Notes and Secured Debt - Annual Principal Payments Due on Debt Obligations (Details)	9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2019 CAD ($)	Sep. 30, 2019 GBP (£)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)
Annual principal payments due
2019	$ 256,322,000
2020	387,398,000
2021	380,866,000
2022	363,548,000
2023	2,118,199,000
Thereafter	8,949,958,000
Totals	12,456,291,000
Senior Unsecured Notes
Annual principal payments due
2019	0
2020	226,501,000
2021	0
2022	10,000,000
2023	1,788,750,000
Thereafter	7,792,025,000
Totals	$ 9,817,276,000			$ 9,699,984,000	$ 9,753,696,000	$ 8,417,447,000
Senior Unsecured Notes \| Minimum
Annual principal payments due
Interest rate	2.79%	2.79%	2.79%
Senior Unsecured Notes \| Maximum
Annual principal payments due
Interest rate	6.50%	6.50%	6.50%
Senior Unsecured Notes \| Canadian-denominated 3.35% senior unsecured notes due 2020
Annual principal payments due
Interest rate	3.35%	3.35%	3.35%
Face amount	$ 226,501,000	$ 300,000,000
Senior Unsecured Notes \| Canadian-denominated unsecured term credit facility
Annual principal payments due
Face amount	$ 188,750,000	$ 250,000,000
Senior Unsecured Notes \| Canadian-denominated unsecured term credit facility \| Canadian Dealer Offered Rate
Annual principal payments due
Debt instrument, basis spread on variable rate	0.90%
Interest rate at period end	2.86%	2.86%	2.86%
Senior Unsecured Notes \| Unsecured term credit facility
Annual principal payments due
Face amount	$ 500,000,000
Senior Unsecured Notes \| Unsecured term credit facility \| LIBOR
Annual principal payments due
Debt instrument, basis spread on variable rate	0.90%
Interest rate at period end	2.96%	2.96%	2.96%
Senior Unsecured Notes \| Senior unsecured notes due 2028
Annual principal payments due
Interest rate	4.80%	4.80%	4.80%
Face amount	$ 676,775,000		£ 550,000,000
Senior Unsecured Notes \| Senior unsecured notes due 2034
Annual principal payments due
Interest rate	4.50%	4.50%	4.50%
Face amount	$ 615,250,000		£ 500,000,000
Secured Debt
Annual principal payments due
2019	256,322,000
2020	160,897,000
2021	380,866,000
2022	353,548,000
2023	329,449,000
Thereafter	1,157,933,000
Totals	2,639,015,000			$ 2,485,711,000	$ 2,479,755,000	$ 2,618,408,000
Carrying values of properties securing the debt	$ 5,922,479,000
Secured Debt \| Minimum
Annual principal payments due
Interest rate	1.39%	1.39%	1.39%
Secured Debt \| Maximum
Annual principal payments due
Interest rate	12.00%	12.00%	12.00%