Supplemental Cash Flow Information - Cash Paid for Interest and Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Supplemental Cash Flow Information [Abstract]
Interest (net of amounts capitalized)	$ 12,597	$ 23,882	$ 23,098
Net income taxes paid (refunds received)	$ 600	$ 1,045	$ (5,271)