Supplemental Cash Flow Information - Supplemental Cash Flow Information (Detail) - USD ($) $ in Thousands	6 Months Ended			12 Months Ended
	Jun. 30, 2019		Jun. 30, 2018	Dec. 31, 2018	[1]
Net cash provided from operating activities included:
Income taxes refunded from taxing authorities			$ 7,521
Interest paid	$ (99,675)		(103,439)
Non-cash investing and financing activities included:
Increase in asset retirement costs capitalized	2,326	[1]	19,561	$ 28,826
Increase (decrease) in accrued capital expenditures	$ 6,346		$ (102,809)

[1] Includes costs incurred whether capitalized or expensed.