Acquisitions (Schedule of Consideration Paid and Net Assets Acquired, Business Acquisitions - WesTower) (Details) - USD ($) $ in Thousands	Oct. 01, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Identifiable assets acquired and liabilities assumed:
Goodwill		$ 988,511	$ 1,082,466	$ 902,000
WesTower [Member]
Acquisition consideration:
Cash	$ 198,000
Acquisition consideration	198,000
Identifiable assets acquired and liabilities assumed:
Accounts receivable	179,800
Other current assets, including $18.0 million of cash acquired	66,600
Business combinations, cash acquired	18,000
Property, equipment and other long-term assets	9,300
Finite-lived intangible assets	42,600
Billings in excess of costs and earnings	(33,300)
Other current liabilities, including current portion of capital lease obligations	(87,700)
Long-term liabilities, including capital lease obligations	(26,400)
Total identifiable net assets	150,900
Goodwill	47,100
Total net assets acquired, including goodwill	$ 198,000