Supplementary Balance Sheet Information - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Line Items]
Cash and cash equivalents, money market accounts	$ 5.0		$ 5.0		$ 2.5
Amortization expense related to conversion costs	3.9	6.0	13.4	17.5
Amortization related to payments for processing rights	$ 3.3	$ 3.2	$ 9.8	$ 10.0
Maximum
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Line Items]
Cash and cash equivalents, money market accounts, original maturity date	90 days		90 days		90 days