Fair Value Measurements - Schedule of Fair Values of Financial Liabilities (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Oct. 31, 2009
Liabilities:
Long-term debt, including current portion	$ 1,196.7
Preferred Stock	49.2		47.9
Preferred Stock		48.4
Total liabilities at fair value	1,245.9	1,240.6
Total liabilities at fair value		1,221.8
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Liabilities:
Long-term debt, including current portion	1,167.3
Preferred Stock	48.4
Total liabilities at fair value	1,215.7
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Liabilities:
Long-term debt, including current portion
Preferred Stock
Total liabilities at fair value
Significant Observable Inputs (Level 2) [Member]
Liabilities:
Long-term debt, including current portion	1,196.7
Preferred Stock	49.2
Total liabilities at fair value	1,245.9
Significant Unobservable Inputs (Level 3) [Member]
Liabilities:
Long-term debt, including current portion
Preferred Stock
Total liabilities at fair value