Property and Equipment (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Property Plant And Equipment [Abstract]
Equipment	$ 6,361,452	$ 5,749,975
Oil and natural gas properties	207,340	183,571
Buildings	83,230	80,050
Land	12,046	12,054
Property, Plant and Equipment, Gross, Total	6,664,068	6,025,650
Less accumulated depreciation and depletion	(2,756,737)	(2,390,109)
Property and equipment, net	$ 3,907,331	$ 3,635,541