Long-Term Debt (Tables)

12 Months Ended

Dec. 31, 2017

Debt Disclosure [Abstract]

Summary of Long-Term Debt

	Year Ended December 31,
	2017 $		2016 $
Revolving credit facilities due through 2022	539,735		466,195
Term loans due through 2021	423,512		475,466
Total principal	963,247		941,661
Less: unamortized discount and debt issuance costs	(10,945	)	(8,645	)
Total debt	952,302		933,016
Less: current portion	(166,745	)	(171,019	)
Non-current portion of long-term debt	785,557		761,997