Acquisitions - Fiscal 2019 Acquisitions (Details) $ in Millions		9 Months Ended
	Oct. 01, 2018 USD ($)	Dec. 31, 2018 USD ($) acquisition	Mar. 31, 2018 USD ($)
Business Acquisition [Line Items]
Goodwill		$ 7,593	$ 7,619
Molina Medicaid Solutions
Business Acquisition [Line Items]
Total consideration transferred	$ 232
Current assets	93
Intangible assets, other than goodwill	69
Other assets	11
Current liabilities	45
Other liabilities	19
Goodwill	$ 123
Estimated useful lives (years)	13 years
Series of Individually Immaterial Business Acquisitions
Business Acquisition [Line Items]
Total consideration transferred		$ 193
Number of acquisitions | acquisition		6
Cash consideration for business acquisition		$ 152
Contingent consideration		$ 41