Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Accrued expenses and reserve liabilities	$ 35	$ 39
Other accrued medical costs	11	12
Net operating losses	13	16
Fixed assets and intangibles	26	30
Unearned premiums	11	9
Lease financing obligation	5	30
Tax credit carryover	11	12
Other	0	3
Valuation allowance	(24)	(28)
Total deferred income tax assets, net of valuation allowance	88	123
Prepaid expenses	(6)	(6)
Other	(3)	0
Total deferred income tax liabilities	(9)	(6)
Net deferred income tax asset	$ 79	$ 117