Subsequent Events - Additional Information (Detail) (USD $) In Millions, unless otherwise specified					1 Months Ended
	Oct. 28, 2012 Short-Term Credit Facility [Member]	Oct. 30, 2011 Short-Term Credit Facility [Member]	Oct. 18, 2013 Subsequent Event [Member] Short-Term Financing Program [Member]	Apr. 29, 2013 Subsequent Event [Member] Short-Term Financing Program [Member]	Dec. 31, 2012 Subsequent Event [Member] Senior Vice President [Member]	Jan. 25, 2013 Subsequent Event [Member] Short-Term Credit Facility [Member]	Oct. 18, 2013 Subsequent Event [Member] Short-Term Credit Facility [Member]
Subsequent Event [Line Items]
Extension to expiry date						Mar. 31, 2015
Line of credit facility, maximum borrowing capacity	$ 195.0			$ 150.0		$ 45.0
Letters of credit maximum available						25
Minimum liquidity requirement						15
Increase in borrowing capacity of facility				200.0
Outstanding under the Short-Term Financing Program and Short-Term Credit Facility	21.9	19.4	150.0				22.4
Severance costs					$ 0.3