Employee Benefits (Fair Value) (Details) - USD ($) $ in Millions | 12 Months Ended | | |
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2016 | Dec. 31, 2015 |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | | | | |
Fair value of plan assets | $ 867.1 | $ 899.3 | $ 878.7 | $ 867.1 |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] | | | | |
Fair value of plan assets beginning of year | 867.1 | 899.3 | | |
Fair value of plan assets at year end | 878.7 | 867.1 | | |
Fair Value, Measurements, Recurring [Member] | | | | |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | | | | |
Investments measured at net asset value | | | 496.3 | 497.4 |
Fair value of plan assets | 867.1 | 867.1 | 878.7 | 867.1 |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] | | | | |
Fair value of plan assets beginning of year | 867.1 | | | |
Fair value of plan assets at year end | 878.7 | 867.1 | | |
Fair Value, Measurements, Recurring [Member] | Level 1 | | | | |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | | | | |
Fair value of plan assets | 187.6 | 187.6 | 184.8 | 187.6 |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] | | | | |
Fair value of plan assets beginning of year | 187.6 | | | |
Fair value of plan assets at year end | 184.8 | 187.6 | | |
Fair Value, Measurements, Recurring [Member] | Level 2 | | | | |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | | | | |
Fair value of plan assets | 137.9 | 137.9 | 155.8 | 137.9 |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] | | | | |
Fair value of plan assets beginning of year | 137.9 | | | |
Fair value of plan assets at year end | 155.8 | 137.9 | | |
Fair Value, Measurements, Recurring [Member] | Level 3 | | | | |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | | | | |
Investments measured at net asset value | | | 496.3 | 497.4 |
Fair value of plan assets | 44.2 | 41.4 | 41.8 | 44.2 |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] | | | | |
Fair value of plan assets beginning of year | 44.2 | 41.4 | | |
Purchases | 6.7 | 4.5 | | |
Sales | (0.6) | (0.7) | | |
Unrealized gain (loss) | (8.5) | (1) | | |
Fair value of plan assets at year end | 41.8 | 44.2 | | |
Fair Value, Measurements, Recurring [Member] | Equities | | | | |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | | | | |
Fair value of plan assets | 83.2 | 83.2 | 87.9 | 83.2 |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] | | | | |
Fair value of plan assets beginning of year | 83.2 | | | |
Fair value of plan assets at year end | 87.9 | 83.2 | | |
Fair Value, Measurements, Recurring [Member] | Equities | Level 1 | | | | |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | | | | |
Fair value of plan assets | 83.2 | 83.2 | 87.9 | 83.2 |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] | | | | |
Fair value of plan assets beginning of year | 83.2 | | | |
Fair value of plan assets at year end | 87.9 | 83.2 | | |
Fair Value, Measurements, Recurring [Member] | Equities | Level 2 | | | | |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | | | | |
Fair value of plan assets | 0 | 0 | 0 | 0 |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] | | | | |
Fair value of plan assets beginning of year | 0 | | | |
Fair value of plan assets at year end | 0 | 0 | | |
Fair Value, Measurements, Recurring [Member] | Equities | Level 3 | | | | |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | | | | |
Fair value of plan assets | 0 | 0 | 0 | 0 |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] | | | | |
Fair value of plan assets beginning of year | 0 | | | |
Fair value of plan assets at year end | 0 | 0 | | |
Fair Value, Measurements, Recurring [Member] | Private equities | | | | |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | | | | |
Fair value of plan assets | 40 | 40 | 38.3 | 40 |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] | | | | |
Fair value of plan assets beginning of year | 40 | | | |
Fair value of plan assets at year end | 38.3 | 40 | | |
Fair Value, Measurements, Recurring [Member] | Private equities | Level 1 | | | | |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | | | | |
Fair value of plan assets | 0 | 0 | 0 | 0 |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] | | | | |
Fair value of plan assets beginning of year | 0 | | | |
Fair value of plan assets at year end | 0 | 0 | | |
Fair Value, Measurements, Recurring [Member] | Private equities | Level 2 | | | | |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | | | | |
Fair value of plan assets | 0 | 0 | 0 | 0 |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] | | | | |
Fair value of plan assets beginning of year | 0 | | | |
Fair value of plan assets at year end | 0 | 0 | | |
Fair Value, Measurements, Recurring [Member] | Private equities | Level 3 | | | | |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | | | | |
Unfunded Commitments | | | 11 | 11.3 |
Investments measured at net asset value | | | 94.6 | 91.1 |
Fair value of plan assets | 40 | 37 | 38.3 | 40 |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] | | | | |
Fair value of plan assets beginning of year | 40 | 37 | | |
Purchases | 4 | 4.5 | | |
Sales | (0.6) | (0.7) | | |
Unrealized gain (loss) | (5.1) | (0.8) | | |
Fair value of plan assets at year end | 38.3 | 40 | | |
Fair Value, Measurements, Recurring [Member] | Corporate | | | | |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | | | | |
Fair value of plan assets | 35.9 | 35.9 | 24.8 | 35.9 |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] | | | | |
Fair value of plan assets beginning of year | 35.9 | | | |
Fair value of plan assets at year end | 24.8 | 35.9 | | |
Fair Value, Measurements, Recurring [Member] | Corporate | Level 1 | | | | |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | | | | |
Fair value of plan assets | 16 | 16 | 5.4 | 16 |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] | | | | |
Fair value of plan assets beginning of year | 16 | | | |
Fair value of plan assets at year end | 5.4 | 16 | | |
Fair Value, Measurements, Recurring [Member] | Corporate | Level 2 | | | | |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | | | | |
Fair value of plan assets | 15.7 | 15.7 | 15.9 | 15.7 |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] | | | | |
Fair value of plan assets beginning of year | 15.7 | | | |
Fair value of plan assets at year end | 15.9 | 15.7 | | |
Fair Value, Measurements, Recurring [Member] | Corporate | Level 3 | | | | |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | | | | |
Fair value of plan assets | 4.2 | 4.2 | 3.5 | 4.2 |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] | | | | |
Fair value of plan assets beginning of year | 4.2 | | | |
Fair value of plan assets at year end | 3.5 | 4.2 | | |
Fair Value, Measurements, Recurring [Member] | Government | | | | |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | | | | |
Fair value of plan assets | 194.5 | 194.5 | 184.1 | 194.5 |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] | | | | |
Fair value of plan assets beginning of year | 194.5 | | | |
Fair value of plan assets at year end | 184.1 | 194.5 | | |
Fair Value, Measurements, Recurring [Member] | Government | Level 1 | | | | |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | | | | |
Fair value of plan assets | 73 | 73 | 72.9 | 73 |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] | | | | |
Fair value of plan assets beginning of year | 73 | | | |
Fair value of plan assets at year end | 72.9 | 73 | | |
Fair Value, Measurements, Recurring [Member] | Government | Level 2 | | | | |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | | | | |
Fair value of plan assets | 121.5 | 121.5 | 111.2 | 121.5 |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] | | | | |
Fair value of plan assets beginning of year | 121.5 | | | |
Fair value of plan assets at year end | 111.2 | 121.5 | | |
Fair Value, Measurements, Recurring [Member] | Government | Level 3 | | | | |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | | | | |
Fair value of plan assets | 0 | 0 | 0 | 0 |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] | | | | |
Fair value of plan assets beginning of year | 0 | | | |
Fair value of plan assets at year end | 0 | 0 | | |
Fair Value, Measurements, Recurring [Member] | Absolute Return | | | | |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | | | | |
Fair value of plan assets | 0.7 | 0.7 | 0 | 0.7 |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] | | | | |
Fair value of plan assets beginning of year | 0.7 | | | |
Fair value of plan assets at year end | 0 | 0.7 | | |
Fair Value, Measurements, Recurring [Member] | Absolute Return | Level 1 | | | | |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | | | | |
Fair value of plan assets | 0 | 0 | 0 | 0 |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] | | | | |
Fair value of plan assets beginning of year | 0 | | | |
Fair value of plan assets at year end | 0 | 0 | | |
Fair Value, Measurements, Recurring [Member] | Absolute Return | Level 2 | | | | |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | | | | |
Fair value of plan assets | 0.7 | 0.7 | 0 | 0.7 |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] | | | | |
Fair value of plan assets beginning of year | 0.7 | | | |
Fair value of plan assets at year end | 0 | 0.7 | | |
Fair Value, Measurements, Recurring [Member] | Absolute Return | Level 3 | | | | |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | | | | |
Investments measured at net asset value | | | 123.8 | 109.8 |
Fair value of plan assets | 0 | 0 | 0 | 0 |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] | | | | |
Fair value of plan assets beginning of year | 0 | | | |
Fair value of plan assets at year end | 0 | 0 | | |
Fair Value, Measurements, Recurring [Member] | Interest bearing | | | | |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | | | | |
Fair value of plan assets | 15.4 | 15.4 | 47.3 | 15.4 |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] | | | | |
Fair value of plan assets beginning of year | 15.4 | | | |
Fair value of plan assets at year end | 47.3 | 15.4 | | |
Fair Value, Measurements, Recurring [Member] | Interest bearing | Level 1 | | | | |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | | | | |
Fair value of plan assets | 15.4 | 15.4 | 18.6 | 15.4 |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] | | | | |
Fair value of plan assets beginning of year | 15.4 | | | |
Fair value of plan assets at year end | 18.6 | 15.4 | | |
Fair Value, Measurements, Recurring [Member] | Interest bearing | Level 2 | | | | |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | | | | |
Fair value of plan assets | 0 | 0 | 28.7 | 0 |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] | | | | |
Fair value of plan assets beginning of year | 0 | | | |
Fair value of plan assets at year end | 28.7 | 0 | | |
Fair Value, Measurements, Recurring [Member] | Interest bearing | Level 3 | | | | |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | | | | |
Fair value of plan assets | 0 | 0 | 0 | 0 |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] | | | | |
Fair value of plan assets beginning of year | 0 | | | |
Fair value of plan assets at year end | 0 | 0 | | |
Fair Value, Measurements, Recurring [Member] | Fixed income | Level 3 | | | | |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | | | | |
Unfunded Commitments | | | 6.2 | 4 |
Investments measured at net asset value | | | 186.2 | 193.1 |
Fair value of plan assets | 4.2 | 4.4 | 3.5 | 4.2 |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] | | | | |
Fair value of plan assets beginning of year | 4.2 | 4.4 | | |
Purchases | 2.7 | 0 | | |
Sales | 0 | 0 | | |
Unrealized gain (loss) | (3.4) | (0.2) | | |
Fair value of plan assets at year end | $ 3.5 | $ 4.2 | | |
Fair Value, Measurements, Recurring [Member] | Equity Funds [Member] | Level 3 | | | | |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | | | | |
Investments measured at net asset value | | | $ 91.7 | $ 103.4 |