Debt (Tables)

3 Months Ended

Mar. 31, 2017

Debt [Abstract]

Schedule of Debt

		Carrying amount
		March 31,		December 31,
			2017		2016
Short-term debt		$	24,616	$	23,912
Long-term debt:
	Revolving loan, denominated in Canadian dollars, unsecured, bearing
	interest at a weighted average rate of 2.426%, due in monthly installments
	of interest only, with the committed, revolving credit facility available until
	October 2021		70,575		69,926
	Revolving loan, denominated in United States dollars, unsecured, bearing
	interest at a weighted average rate of 2.280%, due in monthly installments
	of interest only, with the committed, revolving credit facility available until
	October 2021		30,000		30,000
	Senior unsecured notes, bearing interest at 5.375% due in semi-annual
	installments, with the full amount of principal due in January 2025		500,000		500,000
	Less: unamortized debt issue costs		(4,137)		(4,220)
			596,438		595,706
Total debt		$	621,054	$	619,618