Acquisitions (Schedule of Business Acquisitions, Consideration Paid and Identifiable Net Assets Acquired) (Details) (USD $)			0 Months Ended							0 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	May 01, 2013 Big Country [Member]	May 02, 2013 Big Country [Member]	May 02, 2013 Big Country [Member] Pre-Qualifications [Member]	May 02, 2013 Big Country [Member] Current Assets [Member]	May 02, 2013 Big Country [Member] Current Liabilities [Member]	May 02, 2013 Big Country [Member] Long-term Debt [Member]	May 02, 2013 Big Country [Member] Deferred Income Taxes [Member]	May 01, 2013 Big Country [Member] Earn-out Arrangements [Member]
Purchase price consideration:
Cash			$ 103,500,000
Fair value of contingent consideration (earn-out liability)										22,800,000
Total consideration transferred			126,300,000
Identifiable assets acquired and liabilities assumed:
Assets						69,000,000
Property and equipment				44,000,000
Pre-qualifications					29,600,000
Finite-lived intangible assets				10,700,000
Liabilities							(21,700,000)	(24,400,000)	(13,100,000)
Total identifiable net assets				94,100,000
Goodwill	891,266,000	824,953,000		32,200,000
Total net assets acquired, including goodwill				$ 126,300,000