Property and Equipment (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Equipment	$ 6,168,403	$ 5,749,975
Oil and natural gas properties	200,205	183,571
Buildings	81,611	80,050
Land	12,055	12,054
Property, Plant and Equipment, Gross, Total	6,462,274	6,025,650
Less accumulated depreciation and depletion	(2,588,664)	(2,390,109)
Property and equipment, net	$ 3,873,610	$ 3,635,541