Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 1,371	$ 1,296	$ 1,345	$ 1,237	$ 1,386	$ 1,287	$ 1,317	$ 1,217	$ 5,249	$ 5,207	$ 4,707
Gross Profit	537	509	526	474	542	505	519	460	2,046	2,026	1,847
Operating income	195	11	171	109	194	176	171	113	486	654	552
Net income	$ 118	$ 65	$ 139	$ 79	$ 225	$ 130	$ 115	$ 79	$ 401	$ 549	$ 331
Basic (in dollars per share)	$ 0.66	$ 0.36	$ 0.77	$ 0.44	$ 1.25	$ 0.73	$ 0.64	$ 0.44	$ 2.23	$ 3.05	$ 1.84
Diluted (in dollars per share)	$ 0.65	$ 0.36	$ 0.77	$ 0.43	$ 1.24	$ 0.72	$ 0.64	$ 0.43	$ 2.21	$ 3.03	$ 1.83