Employee Benefit Plans US Pension Assets, Fair Value Measurement by Input Level (Details) - Pension Benefits, U.S. Plans - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	$ 1,449.2	$ 1,399.6
Fair Value, Inputs, Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	299.2	380.1
Fair Value, Inputs, Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	316.7	306.3
Fair Value, Inputs, Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
NAV as a Practical Expedient
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	833.3	713.2
Equity Securities | U.S. Large Cap
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	85.5	176.2
Equity Securities | U.S. Large Cap | Fair Value, Inputs, Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
Equity Securities | U.S. Large Cap | Fair Value, Inputs, Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
Equity Securities | U.S. Large Cap | Fair Value, Inputs, Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
Equity Securities | U.S. Large Cap | NAV as a Practical Expedient
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	85.5	176.2
Equity Securities | U.S. Mid Cap
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets		55.0
Equity Securities | U.S. Mid Cap | Fair Value, Inputs, Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets		0.0
Equity Securities | U.S. Mid Cap | Fair Value, Inputs, Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets		0.0
Equity Securities | U.S. Mid Cap | Fair Value, Inputs, Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets		0.0
Equity Securities | U.S. Mid Cap | NAV as a Practical Expedient
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets		55.0
Equity Securities | U.S. Small Cap
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	50.2	56.9
Equity Securities | U.S. Small Cap | Fair Value, Inputs, Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	50.2	56.9
Equity Securities | U.S. Small Cap | Fair Value, Inputs, Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
Equity Securities | U.S. Small Cap | Fair Value, Inputs, Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
Equity Securities | U.S. Small Cap | NAV as a Practical Expedient
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
Equity Securities | Global Equity Securities
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	259.7
Equity Securities | Global Equity Securities | Fair Value, Inputs, Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0
Equity Securities | Global Equity Securities | Fair Value, Inputs, Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0
Equity Securities | Global Equity Securities | Fair Value, Inputs, Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0
Equity Securities | Global Equity Securities | NAV as a Practical Expedient
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	259.7
Equity Securities | International Securities
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	26.3	126.6
Equity Securities | International Securities | Fair Value, Inputs, Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	63.7
Equity Securities | International Securities | Fair Value, Inputs, Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
Equity Securities | International Securities | Fair Value, Inputs, Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
Equity Securities | International Securities | NAV as a Practical Expedient
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	26.3	62.9
Equity Securities | Emerging Markets
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	49.6	35.5
Equity Securities | Emerging Markets | Fair Value, Inputs, Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
Equity Securities | Emerging Markets | Fair Value, Inputs, Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
Equity Securities | Emerging Markets | Fair Value, Inputs, Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
Equity Securities | Emerging Markets | NAV as a Practical Expedient
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	49.6	35.5
United States Government and Government Agencies and Authorities
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	238.9	244.3
United States Government and Government Agencies and Authorities | Fair Value, Inputs, Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	227.8	231.5
United States Government and Government Agencies and Authorities | Fair Value, Inputs, Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	11.1	12.8
United States Government and Government Agencies and Authorities | Fair Value, Inputs, Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
United States Government and Government Agencies and Authorities | NAV as a Practical Expedient
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
Corporate Debt Securities
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	303.6	291.4
Corporate Debt Securities | Fair Value, Inputs, Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
Corporate Debt Securities | Fair Value, Inputs, Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	303.6	291.4
Corporate Debt Securities | Fair Value, Inputs, Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
Corporate Debt Securities | NAV as a Practical Expedient
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
States, Municipalities, and Political Subdivisions
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	2.0	2.1
States, Municipalities, and Political Subdivisions | Fair Value, Inputs, Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
States, Municipalities, and Political Subdivisions | Fair Value, Inputs, Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	2.0	2.1
States, Municipalities, and Political Subdivisions | Fair Value, Inputs, Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
States, Municipalities, and Political Subdivisions | NAV as a Practical Expedient
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
Opportunistic Credits
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	181.8	163.5
Opportunistic Credits | Fair Value, Inputs, Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
Opportunistic Credits | Fair Value, Inputs, Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
Opportunistic Credits | Fair Value, Inputs, Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
Opportunistic Credits | NAV as a Practical Expedient
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	181.8	163.5
Real Estate
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	88.9	83.5
Real Estate | Fair Value, Inputs, Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
Real Estate | Fair Value, Inputs, Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
Real Estate | Fair Value, Inputs, Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
Real Estate | NAV as a Practical Expedient
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	88.9	83.5
Private Equity Direct Investments
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	37.4	30.4
Private Equity Direct Investments | Fair Value, Inputs, Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
Private Equity Direct Investments | Fair Value, Inputs, Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
Private Equity Direct Investments | Fair Value, Inputs, Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
Private Equity Direct Investments | NAV as a Practical Expedient
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	37.4	30.4
Private Equity Funds
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	32.0	35.3
Private Equity Funds | Fair Value, Inputs, Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
Private Equity Funds | Fair Value, Inputs, Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
Private Equity Funds | Fair Value, Inputs, Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
Private Equity Funds | NAV as a Practical Expedient
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	32.0	35.3
Hedge Funds
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	72.1	70.9
Hedge Funds | Fair Value, Inputs, Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
Hedge Funds | Fair Value, Inputs, Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
Hedge Funds | Fair Value, Inputs, Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
Hedge Funds | NAV as a Practical Expedient
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	72.1	70.9
Cash and Cash Equivalents
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	21.2	28.0
Cash and Cash Equivalents | Fair Value, Inputs, Level 1
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	21.2	28.0
Cash and Cash Equivalents | Fair Value, Inputs, Level 2
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
Cash and Cash Equivalents | Fair Value, Inputs, Level 3
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	0.0	0.0
Cash and Cash Equivalents | NAV as a Practical Expedient
Defined Benefit Plans and Other Postretirement Benefit Plans
Fair Value of Invested Pension Assets	$ 0.0	$ 0.0