Employee Benefit Plans (Details 2) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Employee Benefit Plans
Expected return on plan assets (as a percent)	3.50%
Plan Assets:
Total plan assets	$ 123.9	$ 112.9	$ 111.3
Target allocations
Bonds including cash (as a percent)	55.00%
Equity investments (as a percent)	30.00%
Real estate and mortgages (as a percent)	15.00%
Estimated Future Benefit Payments
2013	7.3
2014	3.9
2015	3.9
2016	4.8
2017	4.8
2018-2022	31.4
Company's contribution
Company's contributions to defined contribution plans	4.6	3.7	2.5
Maximum
Employee Benefit Plans
Discount rate (as a percent)	4.10%	5.50%	5.60%
Expected return on plan assets (as a percent)		4.00%	4.30%
Expected rate of compensation increase (as a percent)	3.80%	3.80%	3.00%
Minimum
Employee Benefit Plans
Discount rate (as a percent)	0.80%	1.10%	1.20%
Expected return on plan assets (as a percent)		3.40%	3.50%
Expected rate of compensation increase (as a percent)	1.00%	1.00%	1.00%
Cash and cash equivalents
Plan Assets:
Total plan assets	12.1	8.3
Debt securities:
Plan Assets:
Total plan assets	52.1	49.4
Debt securities: U.S. corporations
Plan Assets:
Total plan assets	1.3
Debt securities: Foreign corporations
Plan Assets:
Total plan assets	7.5	12.5
Debt securities: Foreign governments
Plan Assets:
Total plan assets	43.3	36.9
Equity Securities:
Plan Assets:
Total plan assets	37.8	34.6
Equity Securities: Foreign corporations
Plan Assets:
Total plan assets	6.4	28.6
Equity Securities: U.S. corporations
Plan Assets:
Total plan assets	31.4	6.0
Real estate
Plan Assets:
Total plan assets	15.0	13.9
Mortgage and other asset-backed securities
Plan Assets:
Total plan assets	6.9	6.7
Quoted Prices in Active Markets Available (Level 1)
Plan Assets:
Total plan assets	117.0	106.2
Quoted Prices in Active Markets Available (Level 1) | Cash and cash equivalents
Plan Assets:
Total plan assets	12.1	8.3
Quoted Prices in Active Markets Available (Level 1) | Debt securities:
Plan Assets:
Total plan assets	52.1	49.4
Quoted Prices in Active Markets Available (Level 1) | Debt securities: U.S. corporations
Plan Assets:
Total plan assets	1.3
Quoted Prices in Active Markets Available (Level 1) | Debt securities: Foreign corporations
Plan Assets:
Total plan assets	7.5	12.5
Quoted Prices in Active Markets Available (Level 1) | Debt securities: Foreign governments
Plan Assets:
Total plan assets	43.3	36.9
Quoted Prices in Active Markets Available (Level 1) | Equity Securities:
Plan Assets:
Total plan assets	37.8	34.6
Quoted Prices in Active Markets Available (Level 1) | Equity Securities: Foreign corporations
Plan Assets:
Total plan assets	6.4	28.6
Quoted Prices in Active Markets Available (Level 1) | Equity Securities: U.S. corporations
Plan Assets:
Total plan assets	31.4	6.0
Quoted Prices in Active Markets Available (Level 1) | Real estate
Plan Assets:
Total plan assets	15.0	13.9
Significant Other Observable Inputs (Level 2)
Plan Assets:
Total plan assets	6.9	6.7
Significant Other Observable Inputs (Level 2) | Mortgage and other asset-backed securities
Plan Assets:
Total plan assets	$ 6.9	$ 6.7