Revenue - Disaggregation of Revenue (Details) - Revenue from Contract with Customer [Member]	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Total net sales	100.00%	100.00%	100.00%	100.00%
CIG
Disaggregation of Revenue [Line Items]
Total net sales	19.30%	19.30%	19.20%	19.50%
Construction
Disaggregation of Revenue [Line Items]
Total net sales	60.40%	58.80%	59.40%	58.60%
CIG
Disaggregation of Revenue [Line Items]
Total net sales	20.30%	21.90%	21.40%	21.90%