Fair Value of Pension Plan Assets (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	$ 497.4	$ 470.8
Balance at beginning of period	85.0	57.2
Actual return on plan assets:
Assets sold during the year	0	0.1
Assets still held at year end	0.9	(1.8)
Net purchases, sales and settlements	2.4	29.5
Balance at end of period	88.3	85.0
Level 1
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	50.9	49.5
Level 2
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	358.2	336.3
Level 3
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	88.3	85.0
Investment funds
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	398.4	369.3
Balance at beginning of period	43.8	53.9
Actual return on plan assets:
Assets sold during the year	0	0.1
Assets still held at year end	2.2	(0.6)
Net purchases, sales and settlements	2.2	(9.6)
Balance at end of period	48.2	43.8
Investment funds | Level 1
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	22.3	18.4
Investment funds | Level 2
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	327.9	307.1
Investment funds | Level 3
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	48.2	43.8
Insurance contracts
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	24.8	24.8
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	24.8	24.8
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	39.8	41.1
Balance at beginning of period	41.1	3.2
Actual return on plan assets:
Assets sold during the year	0	0
Assets still held at year end	(1.3)	(1.2)
Net purchases, sales and settlements	0	39.1
Balance at end of period	39.8	41.1
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	39.8	41.1
Other plan assets
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	34.4	35.6
Balance at beginning of period	0.1	0.1
Actual return on plan assets:
Assets sold during the year	0	0
Assets still held at year end	0	0
Net purchases, sales and settlements	0.2	0
Balance at end of period	0.3	0.1
Other plan assets | Level 1
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	28.6	31.1
Other plan assets | Level 2
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	5.5	4.4
Other plan assets | Level 3
Fair value assets and liabilities measured on recurring and nonrecurring basis
Fair Value of Plan Assets	$ 0.3	$ 0.1