Business Segments (Major Customers) (Details) - Customer Concentration Risk - Sales Revenue, Net	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenue, Major Customer [Line Items]
Concentration risk, percentage	10.00%	10.00%	10.00%
AT&T Mobility
Revenue, Major Customer [Line Items]
Concentration risk, percentage	21.00%	24.00%	20.00%
Verizon Wireless
Revenue, Major Customer [Line Items]
Concentration risk, percentage	15.00%	16.00%	11.00%
Sprint Nextel
Revenue, Major Customer [Line Items]
Concentration risk, percentage	11.00%	13.00%	15.00%
T-Mobile
Revenue, Major Customer [Line Items]
Concentration risk, percentage	9.00%	10.00%	10.00%