CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Accounts receivable, allowances	$ 36.0	$ 36.6
Property and equipment, accumulated depreciation	$ 731.8	$ 706.0
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	10,000,000	10,000,000
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	1,000,000,000	1,000,000,000
Common stock, shares issued	342,902,272	342,902,272
Treasury stock, shares	150,981,594	151,932,157
Series common stock
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	10,000,000	10,000,000