Derivative Instruments (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 CAD ($) properties swap_agreements	Jan. 10, 2020 USD ($) $ / $	Jan. 10, 2020 CAD ($) $ / $	Dec. 31, 2019 USD ($) $ / $	Dec. 31, 2019 CAD ($) $ / $	Dec. 31, 2018 USD ($)
Derivative Liability, Fair Value, Gross Liability				$ 4,500,000		$ 0
Derivative Asset, Fair Value, Gross Asset				1,100,000		$ 10,600,000
Derivative, Notional Amount				25,000,000.0
Derivative Liability, Fair Value, Amount Not Offset Against Collateral				4,000,000.0
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				200,000
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				$ 1,800,000
Cross Currency Swaps 2020 [Member]
Derivative, Forward Exchange Rate | $ / $				1.26	1.26
Cross Currency Swap 2023 [Member]
Number of Canadian properties exposed to foreign currency exchange risk | properties	4
Cross Currency Swap 2023 [Member] | Net Investment Hedging [Member]
Derivative, Notional Amount				$ 100.0
Description of Foreign Currency Exposure	$ 4.5
Maximum [Member]
credit risk related contingent features default on debt amount				50,000,000.0
Maximum [Member] | Interest Rate Swap [Member]
Number of entered into interest rate swap agreements | swap_agreements	4
Derivative, Notional Amount				400,000,000.0
Canada, Dollars | Cross Currency Swaps 2020 [Member]
Monthly CAD Denominated Cash Flows Properties Under Hedges of Foreign Exchange Risk				$ 13,500,000
Derivative, Notional Amount					$ 100.0
Canada, Dollars | Cross Currency Swap 2023 [Member] | Net Investment Hedging [Member]
Derivative, Forward Exchange Rate				1.32	1.32
United States of America, Dollars | Cross Currency Swaps 2020 [Member]
Derivative, Notional Amount				$ 79,500,000
interest rate swap 3.1450 percent [Member] | Interest Rate Swap [Member]
Derivative, Fixed Interest Rate				3.145%	3.145%
Derivative, Notional Amount				$ 116,700,000
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
interest rate swap 3.1575 percent [Member] | Interest Rate Swap [Member]
Derivative, Fixed Interest Rate				3.1575%	3.1575%
Derivative, Notional Amount				$ 116,700,000
interest rate swap 3.1580 percent [Member] | Interest Rate Swap [Member]
Derivative, Fixed Interest Rate				3.158%	3.158%
Derivative, Notional Amount				$ 116,600,000
interest rate swap 3.35 percent [Member] | Interest Rate Swap [Member]
Derivative, Fixed Interest Rate				3.345%	3.345%
Derivative, Notional Amount				$ 50,000,000.0
Subsequent Event [Member] | Cross Currency Swaps 2022 [Member]
Derivative, Forward Exchange Rate | $ / $		1.31	1.31
Subsequent Event [Member] | Canada, Dollars | Cross Currency Swaps 2022 [Member]
Monthly CAD Denominated Cash Flows Properties Under Hedges of Foreign Exchange Risk		$ 7,200,000
Derivative, Notional Amount			$ 100.0
Subsequent Event [Member] | United States of America, Dollars | Cross Currency Swaps 2022 [Member]
Derivative, Notional Amount		$ 76,600,000