CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Accounts receivable, allowance for doubtful accounts	$ 71	$ 62
Property and equipment, accumulated depreciation	1,367	1,233
Customer relationships, accumulated amortization	5,299	4,871
Other intangibles, accumulated amortization	$ 2,134	$ 1,965
Common stock, par value (in dollars per share)	$ 0	$ 0.01
Common stock, authorized shares (in shares)	0	1,000
Common stock, issued shares (in shares)	0	1,000
Class A Common Stock
Common stock, par value (in dollars per share)	$ 0.01	$ 0
Common stock, authorized shares (in shares)	1,600,000,000	0
Common stock, issued shares (in shares)	179,873,244	0
Common stock, outstanding shares (in shares)	179,873,244	0
Class B Common Stock
Common stock, par value (in dollars per share)	$ 0.01	$ 0
Common stock, authorized shares (in shares)	800,000,000	0
Common stock, issued shares (in shares)	719,330,114	0
Common stock, outstanding shares (in shares)	719,330,114	0