Debt Issuance Costs - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Debt Issuance Costs [Line Items]
Net debt issuance costs	$ 12.4		$ 12.4		$ 13.9
Debt issuance costs			4.8
Amortization of debt issuance costs	1.3	0.8	0.5	1.5
Extinguished Indebtedness [Member]
Debt Issuance Costs [Line Items]
Debt issuance cost charged to interest expense			5.0
Other current assets [Member]
Debt Issuance Costs [Line Items]
Net debt issuance costs	$ 2.2		$ 2.2		$ 3.1