Schedule II-Valuation and Qualifying Accounts (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Allowance For Loss On Receivables
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 85		$ 52		$ 51
Acquired Balances	0		0		0
Charged (Credited) to Costs and Expenses	26		31		19
Charged to Other Accounts	8	[1]	22	[1]	(1)	[1]
Deductions or Write-offs	(25)		(20)		(17)
Balance at End of Period	94		85		52
Deferred Tax Asset Valuation Allowance
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	(28)		(28)		(30)
Acquired Balances	0		0		0
Charged (Credited) to Costs and Expenses	0		0		2
Charged to Other Accounts	0	[1]	0	[1]	0	[1]
Deductions or Write-offs	0		0		0
Balance at End of Period	$ (28)		$ (28)		$ (28)

[1] Represents changes in retroactive membership adjustments to premiums revenue and contractual allowances adjustments to services revenue as more fully described in Note 2 to the consolidated financial statements.