Employee Benefits Schedule of fair value of financial assets for pension and postretirement benefits (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 423.9	$ 398.1
Domestic equity mutual funds [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	2.1	2.6
Fixed income mutual funds [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	62.7	53.7
Inflation protection mutual funds [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	19.5
Corporate bonds [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	1.9	2.0
U.S. government securities [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	3.1	3.2
Cash equivalent commingled funds [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	3.0	3.5
Domestic equity index commingled funds [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	145.8	160.9
Foreign equity growth commingled funds [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	28.2	52.7
Foreign equity index commingled funds [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	43.0	36.7
Corporate debt commingled funds [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	65.7	45.7
Inflation protection commingled funds [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	18.7
Foreign equity growth 103-12 investment entities [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	30.2	37.1
Level 1 [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	84.3	56.3
Level 1 [Member] | Domestic equity mutual funds [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	2.1	2.6
Level 1 [Member] | Fixed income mutual funds [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	62.7	53.7
Level 1 [Member] | Inflation protection mutual funds [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	19.5
Level 1 [Member] | Corporate bonds [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Level 1 [Member] | U.S. government securities [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Level 1 [Member] | Cash equivalent commingled funds [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Level 1 [Member] | Domestic equity index commingled funds [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Level 1 [Member] | Foreign equity growth commingled funds [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Level 1 [Member] | Foreign equity index commingled funds [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Level 1 [Member] | Corporate debt commingled funds [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Level 1 [Member] | Inflation protection commingled funds [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0
Level 1 [Member] | Foreign equity growth 103-12 investment entities [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Level 2 [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	339.6	341.8
Level 2 [Member] | Domestic equity mutual funds [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Level 2 [Member] | Fixed income mutual funds [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Level 2 [Member] | Inflation protection mutual funds [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0
Level 2 [Member] | Corporate bonds [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	1.9	2.0
Level 2 [Member] | U.S. government securities [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	3.1	3.2
Level 2 [Member] | Cash equivalent commingled funds [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	3.0	3.5
Level 2 [Member] | Domestic equity index commingled funds [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	145.8	160.9
Level 2 [Member] | Foreign equity growth commingled funds [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	28.2	52.7
Level 2 [Member] | Foreign equity index commingled funds [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	43.0	36.7
Level 2 [Member] | Corporate debt commingled funds [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	65.7	45.7
Level 2 [Member] | Inflation protection commingled funds [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	18.7
Level 2 [Member] | Foreign equity growth 103-12 investment entities [Member]
Defined Benefit Plan Disclosure Fair Value [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 30.2	$ 37.1