Retirement Benefits (Fair Value Disclosures) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016		Dec. 31, 2015
Defined Benefit Plan, Percentage of Global Investments in Plan Assets		80.00%
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		$ 1,961.2		$ 1,943.7
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		1,943.7		1,918.7
Defined Benefit Plan, Business Combinations and Acquisitions, Plan Assets		0.0		0.0
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		10,179.7		9,995.6
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		9,995.6		9,835.7
Defined Benefit Plan, Business Combinations and Acquisitions, Plan Assets		$ 0.0		235.9
Fixed Income Funds [Member]
Defined Benefit Plan, Target Allocation Percentage of Assets		20.00%
Fixed Income Funds [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		$ 68.0		61.2
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		61.2
Fixed Income Funds [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		2,631.3		1,309.9
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		1,309.9
Fixed Income Funds - Repurchased Agreements [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		(1,024.4)
Equity Funds [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		116.0		104.5
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		104.5
Equity Funds [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		1,355.0		1,221.6
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		$ 1,221.6
Equity Securities [Member]
Defined Benefit Plan, Target Allocation Percentage of Assets		80.00%
Equity Securities [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		$ 38.7		40.1
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		40.1
Equity Securities [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		402.4		414.3
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		414.3
Equity Securities - International [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		146.3		144.7
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		144.7
Equity Securities - International [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		2,285.6		2,261.7
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		2,261.7
Fixed Income Funds, Emerging Markets [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		42.6		36.9
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		36.9
Fixed Income Funds, Emerging Markets [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		450.0		472.3
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		472.3
Hedge Funds [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		261.0		272.3
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		272.3
Hedge Funds [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		2,904.6		3,073.2
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		3,073.2
Real Estate [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		34.8		33.2
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		33.2
Real Estate [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		504.1		541.1
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		541.1
Other Assets [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		45.5		42.6
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		42.6
Other Assets [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		671.1		701.5
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		701.5
Other Contract [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		1,208.3		1,208.2
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		1,208.2
Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		1.7		1.7
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		1.7
Fair Value, Inputs, Level 3 [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		17.1		17.1
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		17.1
Fair Value, Inputs, Level 3 [Member] | Fixed Income Funds [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.0		0.0
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		0.0
Fair Value, Inputs, Level 3 [Member] | Fixed Income Funds [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.0		0.0
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		0.0
Fair Value, Inputs, Level 3 [Member] | Fixed Income Funds - Repurchased Agreements [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.0
Fair Value, Inputs, Level 3 [Member] | Equity Funds [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		1.7		1.7
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		1.7
Fair Value, Inputs, Level 3 [Member] | Equity Funds [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		16.8		16.8
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		16.8
Fair Value, Inputs, Level 3 [Member] | Equity Securities [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.0		0.0
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		0.0
Fair Value, Inputs, Level 3 [Member] | Equity Securities [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.0		0.0
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		0.0
Fair Value, Inputs, Level 3 [Member] | Equity Securities - International [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.0		0.0
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		0.0
Fair Value, Inputs, Level 3 [Member] | Equity Securities - International [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.0		0.0
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		0.0
Fair Value, Inputs, Level 3 [Member] | Fixed Income Funds, Emerging Markets [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.0		0.0
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		0.0
Fair Value, Inputs, Level 3 [Member] | Fixed Income Funds, Emerging Markets [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.3		0.3
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		0.3
Fair Value, Inputs, Level 3 [Member] | Hedge Funds [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.0		0.0
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		0.0
Fair Value, Inputs, Level 3 [Member] | Hedge Funds [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.0		0.0
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		0.0
Fair Value, Inputs, Level 3 [Member] | Real Estate [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.0		0.0
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		0.0
Fair Value, Inputs, Level 3 [Member] | Real Estate [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.0		0.0
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		0.0
Fair Value, Inputs, Level 3 [Member] | Other Assets [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.0		0.0
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		0.0
Fair Value, Inputs, Level 3 [Member] | Other Assets [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.0		0.0
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		0.0
Fair Value, Inputs, Level 3 [Member] | Other Contract [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.0		0.0
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		0.0
Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		1,288.6		1,276.9
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		1,276.9
Fair Value, Inputs, Level 2 [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		1,247.0		992.1
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		992.1
Fair Value, Inputs, Level 2 [Member] | Fixed Income Funds [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		58.4		52.9
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		52.9
Fair Value, Inputs, Level 2 [Member] | Fixed Income Funds [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		1,983.0		745.9
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		745.9
Fair Value, Inputs, Level 2 [Member] | Fixed Income Funds - Repurchased Agreements [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		(1,024.4)
Fair Value, Inputs, Level 2 [Member] | Equity Funds [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.0		0.0
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		0.0
Fair Value, Inputs, Level 2 [Member] | Equity Funds [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.2		0.3
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		0.3
Fair Value, Inputs, Level 2 [Member] | Equity Securities [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.0		0.0
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		0.0
Fair Value, Inputs, Level 2 [Member] | Equity Securities [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.0		0.0
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		0.0
Fair Value, Inputs, Level 2 [Member] | Equity Securities - International [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.0		0.0
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		0.0
Fair Value, Inputs, Level 2 [Member] | Equity Securities - International [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.0		0.0
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		0.0
Fair Value, Inputs, Level 2 [Member] | Fixed Income Funds, Emerging Markets [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		18.2		15.3
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		15.3
Fair Value, Inputs, Level 2 [Member] | Fixed Income Funds, Emerging Markets [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		180.1		151.5
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		151.5
Fair Value, Inputs, Level 2 [Member] | Hedge Funds [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.0		0.0
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		0.0
Fair Value, Inputs, Level 2 [Member] | Hedge Funds [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.0		0.0
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		0.0
Fair Value, Inputs, Level 2 [Member] | Real Estate [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.0		0.0
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		0.0
Fair Value, Inputs, Level 2 [Member] | Real Estate [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.0		0.0
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		0.0
Fair Value, Inputs, Level 2 [Member] | Other Assets [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		3.7		0.5
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		0.5
Fair Value, Inputs, Level 2 [Member] | Other Assets [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		108.1		94.4
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		94.4
Fair Value, Inputs, Level 2 [Member] | Other Contract [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		1,208.3		1,208.2
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		1,208.2
Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		131.6		127.9
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		127.9
Fair Value, Inputs, Level 1 [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		1,672.7		1,519.2
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		1,519.2
Fair Value, Inputs, Level 1 [Member] | Fixed Income Funds [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.0		0.0
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		0.0
Fair Value, Inputs, Level 1 [Member] | Fixed Income Funds [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		27.2		0.0
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		0.0
Fair Value, Inputs, Level 1 [Member] | Fixed Income Funds - Repurchased Agreements [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.0
Fair Value, Inputs, Level 1 [Member] | Equity Funds [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.0		0.0
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		0.0
Fair Value, Inputs, Level 1 [Member] | Equity Funds [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.0		0.0
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		0.0
Fair Value, Inputs, Level 1 [Member] | Equity Securities [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		16.7		18.2
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		18.2
Fair Value, Inputs, Level 1 [Member] | Equity Securities [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		165.5		180.1
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		180.1
Fair Value, Inputs, Level 1 [Member] | Equity Securities - International [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		52.0		51.5
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		51.5
Fair Value, Inputs, Level 1 [Member] | Equity Securities - International [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		770.5		751.5
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		751.5
Fair Value, Inputs, Level 1 [Member] | Fixed Income Funds, Emerging Markets [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.0		0.0
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		0.0
Fair Value, Inputs, Level 1 [Member] | Fixed Income Funds, Emerging Markets [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.0		0.0
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		0.0
Fair Value, Inputs, Level 1 [Member] | Hedge Funds [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.0		0.0
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		0.0
Fair Value, Inputs, Level 1 [Member] | Hedge Funds [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.0		2.4
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		2.4
Fair Value, Inputs, Level 1 [Member] | Real Estate [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		34.8		33.2
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		33.2
Fair Value, Inputs, Level 1 [Member] | Real Estate [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		344.5		329.6
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		329.6
Fair Value, Inputs, Level 1 [Member] | Other Assets [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		28.1		25.0
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		25.0
Fair Value, Inputs, Level 1 [Member] | Other Assets [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		365.0		255.6
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		255.6
Fair Value, Inputs, Level 1 [Member] | Other Contract [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.0		0.0
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance		0.0
Fair Value, Retirement Benefits, Investments Valued at Net Asset Value [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		539.3	[1]	537.2	[2]
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance	[2]	537.2
Fair Value, Retirement Benefits, Investments Valued at Net Asset Value [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		7,242.9	[1]	7,467.2	[2]
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance	[2]	7,467.2
Fair Value, Retirement Benefits, Investments Valued at Net Asset Value [Member] | Fixed Income Funds [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		9.6	[1]	8.3	[2]
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance	[2]	8.3
Fair Value, Retirement Benefits, Investments Valued at Net Asset Value [Member] | Fixed Income Funds [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		621.1	[1]	564.0	[2]
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance	[2]	564.0
Fair Value, Retirement Benefits, Investments Valued at Net Asset Value [Member] | Fixed Income Funds - Repurchased Agreements [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance	[1]	0.0
Fair Value, Retirement Benefits, Investments Valued at Net Asset Value [Member] | Equity Funds [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		114.3	[1]	102.8	[2]
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance	[2]	102.8
Fair Value, Retirement Benefits, Investments Valued at Net Asset Value [Member] | Equity Funds [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		1,338.0	[1]	1,204.5	[2]
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance	[2]	1,204.5
Fair Value, Retirement Benefits, Investments Valued at Net Asset Value [Member] | Equity Securities [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		22.0	[1]	21.9	[2]
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance	[2]	21.9
Fair Value, Retirement Benefits, Investments Valued at Net Asset Value [Member] | Equity Securities [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		236.9	[1]	234.2	[2]
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance	[2]	234.2
Fair Value, Retirement Benefits, Investments Valued at Net Asset Value [Member] | Equity Securities - International [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		94.3	[1]	93.2	[2]
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance	[2]	93.2
Fair Value, Retirement Benefits, Investments Valued at Net Asset Value [Member] | Equity Securities - International [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		1,515.1	[1]	1,510.2	[2]
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance	[2]	1,510.2
Fair Value, Retirement Benefits, Investments Valued at Net Asset Value [Member] | Fixed Income Funds, Emerging Markets [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		24.4	[1]	21.6	[2]
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance	[2]	21.6
Fair Value, Retirement Benefits, Investments Valued at Net Asset Value [Member] | Fixed Income Funds, Emerging Markets [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		269.6	[1]	320.5	[2]
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance	[2]	320.5
Fair Value, Retirement Benefits, Investments Valued at Net Asset Value [Member] | Hedge Funds [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		261.0	[1]	272.3	[2]
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance	[2]	272.3
Fair Value, Retirement Benefits, Investments Valued at Net Asset Value [Member] | Hedge Funds [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		2,904.6	[1]	3,070.8	[2]
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance	[2]	3,070.8
Fair Value, Retirement Benefits, Investments Valued at Net Asset Value [Member] | Real Estate [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.0	[1]	0.0	[2]
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance	[2]	0.0
Fair Value, Retirement Benefits, Investments Valued at Net Asset Value [Member] | Real Estate [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		159.6	[1]	211.5	[2]
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance	[2]	211.5
Fair Value, Retirement Benefits, Investments Valued at Net Asset Value [Member] | Other Assets [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		13.7	[1]	17.1	[2]
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance	[2]	17.1
Fair Value, Retirement Benefits, Investments Valued at Net Asset Value [Member] | Other Assets [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		198.0	[1]	351.5	[2]
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance	[2]	351.5
Fair Value, Retirement Benefits, Investments Valued at Net Asset Value [Member] | Other Contract [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Fair Value of Plan Assets, Ending Balance		0.0	[1]	$ 0.0	[2]
Defined Benefit Plan, Fair Value of Plan Assets, Beginning Balance	[2]	$ 0.0

[1] (1) Certain investments that are measured at fair value using the NAV per share (or its equivalent) as a practical expedient have not been classified in the fair value hierarchy.

[2] (1) Certain investments that are measured at fair value using the NAV per share (or its equivalent) as a practical expedient have not been classified in the fair value hierarchy.