Acquisitions - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Goodwill acquired	$ 3,699	$ 3,733
Other intangible assets useful life, years	10 years 4 months 24 days
American Eldercare Inc.
Business Acquisition [Line Items]
Date of acquisition	Sep. 06, 2013
Goodwill acquired	76
Amount allocated to other intangible assets	$ 75
Other intangible assets useful life, years	9 years 3 months 18 days