Pension and Savings Plans (Details 4) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	$ 769.6	$ 771.6
Level 1 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	0	82.6
Level 2 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	744.3	641.3
Level 3 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	25.3	47.7
U.S. equity securities
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	340.4	333.1
U.S. equity securities | Level 1 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	0	82.6
U.S. equity securities | Level 2 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	340.4	250.5
U.S. equity securities | Level 3 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	0	0
International equity securities
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	107.8	118.9
International equity securities | Level 1 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	0	0
International equity securities | Level 2 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	107.8	118.9
International equity securities | Level 3 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	0	0
Collateralized Mortgage Backed Securities [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	98.9	108.8
Collateralized Mortgage Backed Securities [Member] | Level 1 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	0	0
Collateralized Mortgage Backed Securities [Member] | Level 2 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	98.9	108.8
Collateralized Mortgage Backed Securities [Member] | Level 3 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	0	0
U.S. debt securities
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	83.3	60.2
U.S. debt securities | Level 1 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	0	0
U.S. debt securities | Level 2 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	83.3	60.2
U.S. debt securities | Level 3 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	0	0
International debt securities
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	32.0	25.7
International debt securities | Level 1 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	0	0
International debt securities | Level 2 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	32.0	25.7
International debt securities | Level 3 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	0	0
Corporate debt securities
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	45.8	46.1
Corporate debt securities | Level 1 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	0	0
Corporate debt securities | Level 2 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	45.8	46.1
Corporate debt securities | Level 3 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	0	0
Short-term investments
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	36.1	31.1
Short-term investments | Level 1 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	0	0
Short-term investments | Level 2 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	36.1	31.1
Short-term investments | Level 3 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	0	0
Interests in real estate
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	25.3	47.7
Interests in real estate | Level 1 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	0	0
Interests in real estate | Level 2 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	0	0
Interests in real estate | Level 3 [Member]
Fair value of assets in the Master Trust by category and by fair value valuation hierarchy
Total assets at fair value	$ 25.3	$ 47.7	$ 47.4