Supplemental Cash Flow Information - Supplemental Cash Flow Information (Detail) - USD ($) $ in Thousands	3 Months Ended			12 Months Ended
	Mar. 31, 2016		Mar. 31, 2015	Dec. 31, 2015	[1]
Net cash provided from operating activities included:
Income taxes refunded from taxing authorities	$ 73		$ 0
Interest paid	(37,117)		(54,284)
Non-cash investing and financing activities included:
Increase in asset retirement costs capitalized	1,015	[1]	15,813	$ 22,184
Increase (decrease) in accrued capital expenditures	$ 9,719		$ (110,622)

[1] Includes costs incurred whether capitalized or expensed.