Acquisitions (Schedule of Consideration Paid and Net Assets Acquired, Business Acquisitions - Pacer) (Details) - USD ($) $ in Thousands		9 Months Ended
	Jun. 01, 2014	Sep. 30, 2014	Sep. 30, 2015	Dec. 31, 2014
Identifiable assets acquired and liabilities assumed:
Goodwill			$ 1,064,822	$ 1,082,466
Earn-Out Arrangements [Member]
Acquisition consideration:
Fair value of contingent consideration (earn-out liability)		$ 33,612
Pacer [Member] | Canadian Dollars [Member]
Acquisition consideration:
Cash	$ 126,500
Total consideration transferred	150,800
Identifiable assets acquired and liabilities assumed:
Current assets, including $3.4 million of cash acquired	114,000
Business combinations, cash acquired	3,400
Property and equipment	81,200
Finite-lived intangible assets	19,400
Current liabilities, including current portion of capital lease obligations and long-term debt	(71,800)
Long-term debt, including capital lease obligations	(69,600)
Deferred income taxes	(30,500)
Total identifiable net assets	50,400
Goodwill	100,400
Total net assets acquired, including goodwill	150,800
Pacer [Member] | Canadian Dollars [Member] | Equity Method Investments [Member]
Identifiable assets acquired and liabilities assumed:
Net equity method investment obligations	(31,000)
Pacer [Member] | Canadian Dollars [Member] | Pre-Qualifications [Member]
Identifiable assets acquired and liabilities assumed:
Pre-qualifications	38,700
Pacer [Member] | Canadian Dollars [Member] | Earn-Out Arrangements [Member]
Acquisition consideration:
Fair value of contingent consideration (earn-out liability)	$ 24,300