CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Accounts receivable, allowance for doubtful accounts	$ 74	$ 71
Property and equipment, accumulated depreciation	1,416	1,367
Customer relationships, accumulated amortization	5,660	5,299
Other intangibles, accumulated amortization	$ 2,365	$ 2,134
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, authorized shares (in shares)	1,000	1,000
Common stock, issued shares (in shares)	1,000	1,000
Class A Common Stock
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, authorized shares (in shares)	1,600,000,000	1,600,000,000
Common stock, issued shares (in shares)	367,893,026	179,873,244
Common stock, outstanding shares (in shares)	367,893,026	179,873,244
Class B Common Stock
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, authorized shares (in shares)	624,998,004	800,000,000
Common stock, issued shares (in shares)	544,066,353	719,330,114
Common stock, outstanding shares (in shares)	544,066,353	719,330,114