Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Accounts receivable, allowances	$ 79	$ 58
Property and equipment, accumulated depreciation	2,435	2,054
Identifiable intangible assets, accumulated amortization	$ 914	$ 850
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	70,000.00	70,000.00
Preferred stock, shares outstanding (in shares)	70,000.00	70,000.00
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	300,000,000	300,000,000
Common stock, shares issued (in shares)	91,000,000	92,000,000
Common stock, shares outstanding (in shares)	91,000,000	92,000,000