Fair Value of Pension Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	$ 461.1	$ 500.7
Balance at beginning of period	88.9	72.5
Assets still held at year end	(9.8)	(1.8)
Net purchases, sales and settlements	3.2	18.6
Balance at end of period	82.3	88.9
Level 1
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	57.1	61.9
Level 2
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	321.7	349.9
Level 3
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	82.3	88.9
Transfers in/out of Level 3	0.0	(0.4)
Investment funds
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	382.3	410.5
Balance at beginning of period	57.9	40.1
Assets still held at year end	(6.8)	(0.7)
Net purchases, sales and settlements	3.2	18.5
Balance at end of period	54.3	57.9
Investment funds | Level 1
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	14.4	16.8
Investment funds | Level 2
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	313.6	335.8
Investment funds | Level 3
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	54.3	57.9
Transfers in/out of Level 3	0.0	0.0
Insurance contracts
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	7.8	13.7
Insurance contracts | Level 1
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	0.0	0.0
Insurance contracts | Level 2
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	7.8	13.7
Insurance contracts | Level 3
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	0.0	0.0
Limited partnerships
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	28.0	31.0
Balance at beginning of period	31.0	32.1
Assets still held at year end	(3.0)	(1.1)
Net purchases, sales and settlements	0.0	0.0
Balance at end of period	28.0	31.0
Limited partnerships | Level 1
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	0.0	0.0
Limited partnerships | Level 2
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	0.0	0.0
Limited partnerships | Level 3
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	28.0	31.0
Transfers in/out of Level 3	0.0	0.0
Fixed Income Funds
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	22.9	22.5
Fixed Income Funds | Level 1
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	22.6	22.1
Fixed Income Funds | Level 2
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	0.3	0.4
Fixed Income Funds | Level 3
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	0.0	0.0
Other plan assets
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	20.1	23.0
Balance at beginning of period	0.0	0.3
Assets still held at year end	0.0	0.0
Net purchases, sales and settlements	0.0	0.1
Balance at end of period	0.0	0.0
Other plan assets | Level 1
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	20.1	23.0
Other plan assets | Level 2
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	0.0	0.0
Other plan assets | Level 3
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	0.0	0.0
Transfers in/out of Level 3	$ 0.0	$ (0.4)