Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Accounts receivable, allowance for doubtful accounts and billing adjustments	$ 4.5	$ 3.9
Property and equipment, accumulated depreciation and amortization	376.8	364.2
Computer software, accumulated amortization	511.0	627.3
Contract acquisition costs, accumulated amortization	226.1	216.0
Other intangible assets, accumulated amortization	$ 66.2	$ 55.2
Common stock, par value	$ 0.10	$ 0.10
Common stock, Authorized	600,000	600,000
Common stock, issued	202,813	202,471
Common stock, outstanding	188,614	187,031
Treasury stock, shares	14,199	15,440