Restricted Investments - Summary of Restricted Investments by Health Plan (Details) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Restricted Investments
Total Health Plans segment	$ 116	$ 109
Health Plans
Restricted Investments
Total Health Plans segment	116	109
Florida | Health Plans
Restricted Investments
Total Health Plans segment	28	34
Illinois | Health Plans
Restricted Investments
Total Health Plans segment	3	0
Michigan | Health Plans
Restricted Investments
Total Health Plans segment	1	1
New Mexico | Health Plans
Restricted Investments
Total Health Plans segment	43	43
New York | Health Plans
Restricted Investments
Total Health Plans segment	9	0
Ohio | Health Plans
Restricted Investments
Total Health Plans segment	12	12
Puerto Rico | Health Plans
Restricted Investments
Total Health Plans segment	10	10
Texas | Health Plans
Restricted Investments
Total Health Plans segment	4	4
Utah | Health Plans
Restricted Investments
Total Health Plans segment	4	4
Wisconsin | Health Plans
Restricted Investments
Total Health Plans segment	1	1
Other | Health Plans
Restricted Investments
Total Health Plans segment	$ 1	$ 0