Supplemental Cash Flow Information - Supplemental Cash Flow Information (Detail) - USD ($) $ in Thousands	6 Months Ended			12 Months Ended
	Jun. 30, 2015		Jun. 30, 2014	Dec. 31, 2014	[1]
Net cash provided from operating activities included:
Income taxes paid to taxing authorities	$ 0		$ 39
Interest paid	73,189		89,381
Non-cash investing and financing activities included:
Increase in asset retirement costs capitalized	18,684	[1]	5,516	$ 56,822
(Decrease) increase in accrued capital expenditures	$ (156,897)		$ 15,211

[1] Includes costs incurred whether capitalized or expensed.