General (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 01, 2015
Organization And Description Of Business [Line Items]
Revenue from Medicaid programs	$ 2,439,071,000	$ 2,196,513,000	$ 7,271,852,000	$ 6,570,732,000
Increase (decrease) in net revenue		21,000,000
Increase (decrease) in other operating expense				71,000,000
Impairment of goodwill or indefinite-lived intangible assets					$ 0
State Medicaid programs
Organization And Description Of Business [Line Items]
Revenue from Medicaid programs	62,000,000	53,000,000	221,000,000	180,000,000
Revenue offset amount	$ 30,000,000	$ 21,000,000	$ 97,000,000	$ 71,000,000