Summary of Fair Values of Metropolitan's Assets Acquired and Liabilities Assumed (Detail) (Metropolitan Health Networks, Inc., USD $) In Millions, unless otherwise specified	Dec. 31, 2012
Metropolitan Health Networks, Inc.
Business Acquisition [Line Items]
Cash and cash equivalents	$ 49
Receivables, net	28
Other current assets	40
Property and equipment	22
Goodwill	569
Other intangible assets	263
Other long-term assets	1
Total assets acquired	972
Current liabilities	(22)
Other long-term liabilities	(99)
Total liabilities assumed	(121)
Net assets acquired	$ 851