Acquisitions (Schedule of Business Acquisition Consideration Paid And Net Assets Acquired) (Details) (USD $)			6 Months Ended		0 Months Ended				0 Months Ended
	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2014 Earn-Out Arrangements [Member]	Jun. 30, 2013 Earn-Out Arrangements [Member]	Jun. 01, 2014 Pacer [Member]	Jun. 01, 2014 Pacer [Member]	Jun. 01, 2014 Pacer [Member] Pre-Qualifications [Member]	Jun. 01, 2014 Pacer [Member] Equity Method Investments [Member]	Jun. 01, 2014 Pacer [Member] Earn-Out Arrangements [Member]
Purchase price consideration:
Cash					$ 126,500,000
Fair value of contingent consideration (earn-out liability)			33,612,000	26,721,000					24,300,000
Total consideration transferred					150,800,000
Identifiable assets acquired and liabilities assumed:
Current assets						118,400,000
Equity method investments								3,500,000
Other long-term assets						8,700,000
Property and equipment						72,800,000
Pre-qualifications							39,200,000
Finite-lived intangible assets						19,600,000
Current liabilities						(48,000,000)
Long-term debt						(87,000,000)
Deferred income taxes						(29,300,000)
Total identifiable net assets						97,900,000
Goodwill	983,133,000	902,044,000				52,900,000
Total net assets acquired, including goodwill						$ 150,800,000