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Labor Union Contracts
3 Months Ended
Mar. 31, 2017
Labor Union Contracts [Abstract]  
Concentration risk disclosure
Labor Union Contracts
Approximately 45% of our employees are members of various bargaining units represented by the Communication Workers of America and the International Brotherhood of Electrical Workers. Approximately 10,000, or 45%, of our employees are subject to collective bargaining agreements that are scheduled to expire October 7, 2017.