Commitments and Contingent Liabilities (Loss Contingencies) (Details) $ in Millions	9 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2015 USD ($)	Dec. 31, 2005 USD ($)	Dec. 31, 2004	Oct. 07, 2015 USD ($)	Jan. 31, 2012 USD ($)
PFOA Matters [Member]
Loss Contingencies [Line Items]
Accrual balance		$ 20.0
Indemnification assets		20.0
PFOA Matters: Drinking Water Actions [Member]
Loss Contingencies [Line Items]
Binding settlement agreement, class size				80,000
Escrow deposit						$ 1.0
Loss contingency, potential additional loss		$ 235.0
PFOA Matters: Additional Actions [Member]
Loss Contingencies [Line Items]
Lawsuits alleging personal injury - filed		3,500
PFOA MDL plaintiffs		6
Lawsuits alleging personal injury - number of new claims filed		600
Compensatory Damages Awarded					$ 1.6
PFOA Matters: Additional Actions - Ohio MDL [Member]
Loss Contingencies [Line Items]
Lawsuits alleging wrongful death		37
Payment for Plaintiffs Attorney Fees [Member] | PFOA Matters: Drinking Water Actions [Member]
Loss Contingencies [Line Items]
Settlement payments			$ 23.0
Payment to fund community health project [Member] | PFOA Matters: Drinking Water Actions [Member]
Loss Contingencies [Line Items]
Settlement payments			$ 70.0
Scenario, Forecast [Member] | PFOA Matters: Additional Actions [Member]
Loss Contingencies [Line Items]
Number of cases for trial in 2017	40