Significant Components of Contract Acquisition Costs, Net of Accumulated Amortization (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Acquired Finite-Lived Intangible Assets [Line Items]
Conversion costs, accumulated amortization	$ 88.5	$ 109.8
Payments for processing rights, accumulated amortization	$ 191.0	$ 186.1