Derivative Instruments (Narrative) (Details) $ in Millions	9 Months Ended
	Sep. 30, 2020 USD ($) $ / $	Sep. 30, 2020 CAD ($) $ / $	Dec. 31, 2019 USD ($)
credit risk related contingent features default on debt amount		$ 50.0
Derivative Liability, Fair Value, Gross Liability	$ 11,700,000		$ 4,500,000
Derivative Asset, Fair Value, Gross Asset	$ 4,000,000.0		$ 1,100,000
Number of entered into interest rate swap agreements (in interest rate swaps)	4	4
Derivative, Notional Amount	$ 25,000,000.0
Derivative, Fixed Rate Increase	0.90%	0.90%
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	$ 10,800,000
Net Investment Hedging [Member]
Derivative, Notional Amount	200.0
Cash Flow Hedging [Member]
Estimated amount to be reclassified from accumulated other comprehensive income to other expense in the next twelve months	100,000
Interest Rate Swap [Member]
Derivative, Notional Amount	400,000,000.0
Interest Rate Risk [Member]
Estimated amount to be reclassified from accumulated other comprehensive income to other expense in the next twelve months	$ 8,200,000
Currency Swap [Member]
Number of Canadian properties exposed to foreign currency exchange risk (in properties)	4
Cross Currency Swaps 2022 [Member]
Net exchange rate, CAD to US dollar | $ / $	1.31	1.31
Cross Currency Swap 2023 [Member] | Net Investment Hedging [Member]
Derivative, Notional Amount	$ 100.0
Net exchange rate, CAD to US dollar	1.32	1.32
Foreign currency exposure	$ 4,500,000
interest rate swap 4.0450 percent | Interest Rate Swap [Member]
Derivative fixed interest rate	4.045%	4.045%
Derivative, Notional Amount	$ 116,700,000
interest rate swap 4.0575 percent [Member] | Interest Rate Swap [Member]
Derivative fixed interest rate	4.0575%	4.0575%
Derivative, Notional Amount	$ 116,700,000
interest rate swap 4.2450 percent [Member] | Interest Rate Swap [Member]
Derivative fixed interest rate	4.058%	4.058%
Derivative, Notional Amount	$ 116,600,000
interest rate swap 4.2450 percent [Member] | Interest Rate Swap [Member]
Derivative fixed interest rate	4.245%	4.245%
Derivative, Notional Amount	$ 50,000,000.0
interest rate swap 1.3925 percent [Member] | Interest Rate Swap [Member]
Derivative fixed interest rate	1.3925%	1.3925%
Derivative, Notional Amount	$ 25,000,000.0
United States of America, Dollars | Cross Currency Swaps 2022 [Member]
Derivative, Notional Amount	76,600,000
Canada, Dollars | Cross Currency Swaps 2022 [Member]
Derivative, Notional Amount		$ 100.0
Monthly CAD Denominated Cash Flows Properties Under Hedges of Foreign Exchange Risk	$ 7,200,000