Condensed Consolidating Financial Information - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Subsidiaries Guarantor [Member]
Condensed Financial Statements, Captions [Line Items]
Change in total assets or liabilities	$ 1,010.4	$ 888.9
Subsidiaries Non Guarantor [Member]
Condensed Financial Statements, Captions [Line Items]
Change in total assets or liabilities	$ 390.9	$ 5.5