Summary of Net Intangible Assets (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Finite Lived Intangible Assets [Line Items]
Net Intangible Assets	$ 220	$ 228
Tradenames
Finite Lived Intangible Assets [Line Items]
Net Intangible Assets	124	124
Medicare Licenses
Finite Lived Intangible Assets [Line Items]
Net Intangible Assets	57	57
Certificates of Need
Finite Lived Intangible Assets [Line Items]
Net Intangible Assets	12	12
Contract Relationships and Other
Finite Lived Intangible Assets [Line Items]
Net Intangible Assets	$ 27	$ 35