Fair Value of Pension Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	$ 500.7	$ 527.0
Balance at beginning of period	72.5	62.1
Actual return on plan assets:
Assets sold during the year	0.0	0.4
Assets still held at year end	(1.8)	(1.3)
Net purchases, sales and settlements	18.6	11.3
Defined Benefit Plan, Transfers Between Measurement Levels	(0.4)	0.0
Balance at end of period	88.9	72.5
Level 1
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	61.9	61.2
Level 2
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	349.9	393.3
Level 3
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	88.9	72.5
Investment funds
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	410.5	431.5
Balance at beginning of period	40.1	25.4
Actual return on plan assets:
Assets sold during the year	0.0	0.2
Assets still held at year end	(0.7)	(0.7)
Net purchases, sales and settlements	18.5	15.2
Defined Benefit Plan, Transfers Between Measurement Levels	0.0	0.0
Balance at end of period	57.9	40.1
Investment funds | Level 1
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	16.8	18.8
Investment funds | Level 2
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	335.8	372.6
Investment funds | Level 3
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	57.9	40.1
Insurance contracts
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	13.7	19.3
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	13.7	19.3
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	31.0	32.1
Balance at beginning of period	32.1	36.1
Actual return on plan assets:
Assets sold during the year	0.0	0.2
Assets still held at year end	(1.1)	(0.3)
Net purchases, sales and settlements	0.0	(3.9)
Defined Benefit Plan, Transfers Between Measurement Levels	0.0	0.0
Balance at end of period	31.0	32.1
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	31.0	32.1
Fixed Income Funds
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	22.5	19.0
Fixed Income Funds | Level 1
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	22.1	17.6
Fixed Income Funds | Level 2
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	0.4	1.4
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	23.0	25.1
Balance at beginning of period	0.3	0.6
Actual return on plan assets:
Assets sold during the year	0.0	0.0
Assets still held at year end	0.0	(0.3)
Net purchases, sales and settlements	0.1	0.0
Defined Benefit Plan, Transfers Between Measurement Levels	(0.4)	0.0
Balance at end of period	0.0	0.3
Other plan assets | Level 1
Fair value assets and liabilities measured on recurring basis
Fair Value of Plan Assets	23.0	24.8
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	$ 0.3