Fair Value of Pension Plan Assets (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	$ 527.0	$ 508.1
Balance at beginning of period	62.1	88.3
Actual return on plan assets:
Assets sold during the year	0.4	0.6
Assets still held at year end	(1.3)	(0.8)
Net purchases, sales and settlements	11.3	(26.0)
Balance at end of period	72.5	62.1
Level 1
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	61.2	62.4
Level 2
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	393.3	383.6
Level 3
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	72.5	62.1
Investment funds
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	431.5	406.7
Balance at beginning of period	25.4	48.2
Actual return on plan assets:
Assets sold during the year	0.2	0.6
Assets still held at year end	(0.7)	1.9
Net purchases, sales and settlements	15.2	(25.3)
Balance at end of period	40.1	25.4
Investment funds | Level 1
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	18.8	22.2
Investment funds | Level 2
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	372.6	359.1
Investment funds | Level 3
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	40.1	25.4
Insurance contracts
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	19.3	22.0
Insurance contracts | Level 1
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	0	0
Insurance contracts | Level 2
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	19.3	22.0
Insurance contracts | Level 3
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	0	0
Limited partnerships
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	32.1	36.1
Balance at beginning of period	36.1	39.8
Actual return on plan assets:
Assets sold during the year	0.2	0
Assets still held at year end	(0.3)	(2.9)
Net purchases, sales and settlements	(3.9)	(0.8)
Balance at end of period	32.1	36.1
Limited partnerships | Level 1
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	0	0
Limited partnerships | Level 2
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	0	0
Limited partnerships | Level 3
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	32.1	36.1
Other plan assets
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	44.1	43.3
Balance at beginning of period	0.6	0.3
Actual return on plan assets:
Assets sold during the year	0	0
Assets still held at year end	(0.3)	0.2
Net purchases, sales and settlements	0	0.1
Balance at end of period	0.3	0.6
Other plan assets | Level 1
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	42.4	40.2
Other plan assets | Level 2
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	1.4	2.5
Other plan assets | Level 3
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	$ 0.3	$ 0.6