Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Accounts receivable, allowances for doubtful accounts, billing adjustments and merchant losses	$ 5.3	$ 4.0
Computer software, accumulated amortization	719.5	680.6
Property and equipment, accumulated depreciation and amortization	$ 473.2	$ 457.3
Common stock, par value	$ 0.10	$ 0.10
Common stock, authorized	600,000,000	600,000,000
Common stock, issued	202,765,000	202,769,000
Common stock, outstanding	183,826,000	182,781,000
Treasury stock, shares	18,939,000	19,988,000
Other intangible assets
Intangible assets, accumulated amortization	$ 327.0	$ 257.1
Contract Acquisition Costs
Intangible assets, accumulated amortization	$ 297.4	$ 287.9