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Labor Union Contracts	3 Months Ended
Labor Union Contracts	Mar. 31, 2018
Labor Union Contracts [Abstract]
Concentration risk disclosure	Labor Union Contracts As of March 31, 2018, approximately 10,000, or 44%, of our employees were members of various bargaining units represented by the Communication Workers of America ("CWA") and the International Brotherhood of Electrical Workers ("IBEW").