Acquisitions (Narrative) (Details)	6 Months Ended
	Jun. 30, 2015
Business Combinations [Abstract]
Business combinations, provisional information, initial accounting incomplete, items	As of June 30, 2015, determination of the fair values of the net assets acquired, including the estimated values of contingent earn-out obligations and the estimated useful lives of acquired assets for the WesTower acquisition, as discussed below, were provisional and remained preliminary. Management continues to assess the valuation of these items and any ultimate purchase price adjustments that may result based on the final net assets and net working capital, as prescribed in the purchase agreement.
Business combinations, provisional information, initial accounting incomplete, reasons	The Company will revise its preliminary estimates of the fair values of net assets acquired if new information is obtained about the facts and circumstances existing as of the date of acquisition or for purchase price adjustments.