Commitments and Contingent Liabilities (Litigation) (Narrative) (Details) $ in Millions	1 Months Ended	7 Months Ended	9 Months Ended	12 Months Ended
	Jul. 31, 2005 USD ($)	Nov. 30, 2016	Dec. 31, 2017	Dec. 31, 2004 resident	Mar. 31, 2016 USD ($)	Oct. 07, 2015 USD ($)	Jan. 31, 2012 USD ($)
PFOA Matters [Member]
Loss Contingencies [Line Items]
Accrual balance					$ 14.0
Indemnification assets					14.0
PFOA Matters: Drinking Water Actions [Member]
Loss Contingencies [Line Items]
Binding settlement agreement, class size | resident				80,000
Loss contingency, potential additional loss					235.0
Escrow deposit							$ 1.0
Minimum escrow amount per settlement agreement							$ 0.5
Escrow amount disbursed (less than)					$ 1.0
PFOA Matters: Additional Actions [Member]
Loss Contingencies [Line Items]
Lawsuits alleging personal injury - Filed					3,500
Portion of lawsuits alleging personal injury claims associated only with high cholesterol and/or thyroid disease					75.00%
Lawsuits alleging wrongful death					30
PFOA MDL plaintiffs					6
Compensatory damages awarded						$ 1.6
Portion of pending lawsuits claiming that exposure to PFOA in drinking water caused cancer (less than)					10.00%
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 2016		3
Number of cases for trial in 2017			40