Activity in Allowance for Credit Losses (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at Beginning of Year	$ 1.5	$ 1.5	$ 1.5
Provisions	0	1.8	0
Charge-offs, Net of Recoveries	0	(1.8)	0
Balance at End of Period	$ 1.5	$ 1.5	$ 1.5