Consolidated Balance Sheets (Parenthetical) - USD ($) shares in Millions, $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Allowance for Doubtful Accounts Receivable, Current	$ 6	$ 6
Preferred Stock, Par or Stated Value Per Share (in dollars per share)	$ 0.01	$ 0.01
Preferred Stock, Shares Authorized (in shares)	100	100
Preferred Stock, Shares Issued (in shares)	0	0
Preferred Stock, Shares Outstanding (in shares)	0	0
Common Stock, Par or Stated Value Per Share (in dollars per share)	$ 0.01	$ 0.01
Common Stock, Shares Authorized (in shares)	1,500	1,500
Common Stock, Shares, Issued (in shares)	603	600
Common Stock, Shares, Outstanding (in shares)	581	583
Treasury Stock, Shares (in shares)	22	17