Supplemental cash flow and non-cash information - Summary (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Supplemental Cash Flow Elements [Abstract]
Interest Paid, Capitalized, Investing Activities	$ 1,181	$ 242
Supplemental cash flow information:
Cash paid for interest	23,697	26,345
Supplemental non-cash investing information:
Increase in accrued capital expenditures	16,272	6,443
Capitalized share-settled equity-based compensation	965	1,899
Capitalized asset retirement cost	886	271
Right-of-use assets obtained in exchange for operating lease liabilities	$ 0	$ 22,090