Supplemental Cash Flow Information - Summary of Supplemental Cash Flow Information (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Noncash Investing Activities [Abstract]
Increase in accrued capital expenditures	$ 235,431	$ 69,767
Asset retirement obligation additions and revisions, net	6,232	5,043
Supplemental Cash Flow Elements [Abstract]
Cash paid for interest	173,057	139,023
Cash paid for income taxes	4,012	23,413
Cash received for income tax refunds	$ (5)	$ (173)