Consolidated Balance Sheets (Parenthetical) - USD ($) shares in Thousands, $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Consolidated Balance Sheets
Accounts receivable, allowances for doubtful accounts and billing adjustments	$ 4.7	$ 5.9
Other intangible assets, accumulated amortization	655.6	600.9
Intangible assets - computer software, accumulated amortization	822.6	849.3
Property and equipment, accumulated depreciation and amortization	$ 520.6	$ 521.1
Common stock, par value (in dollars per share)	$ 0.10	$ 0.10
Common stock, authorized (in shares)	600,000	600,000
Common stock, issued (in shares)	202,765	202,765
Common stock, outstanding (in shares)	182,305	180,903
Treasury stock (in shares)	20,460	21,862