Supplemental Cash Flow Information - Summary of Supplemental Cash Flow Information (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Supplemental Cash Flow Elements [Abstract]
Cash paid for interest	$ 52,251	$ 57,952
Cash paid for income taxes	0	2
Cash received for income tax refunds	5	148
Noncash Investing and Financing Items [Abstract]
Accrued capital expenditures	301,500		$ 302,800
Increase (Decrease) in Asset Retirement Obligations	$ 1,609	$ 1,565