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Summary of Activities Related to Unrecognized Tax Benefits (Detail) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Schedule of Unrecognized Tax Benefits [Line Items]    
Beginning Balance $ 4.3 $ 3.8
Increases related to current year tax 0.2 1.3
Decreases due to settlements with tax authorities   (0.2)
Increases from prior period positions 0.1  
Decreases from prior period positions (0.2)  
Decreases due to lapse of statute of limitations (0.4) (0.6)
Ending Balance $ 4.0 $ 4.3