Acquisitions - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended		0 Months Ended		0 Months Ended
	Sep. 30, 2014	Dec. 31, 2013	Sep. 06, 2013 American Eldercare Inc.	Sep. 06, 2013 American Eldercare Inc.	Sep. 06, 2013 Customer Contracts and Technology American Eldercare Inc.
Business Acquisition [Line Items]
Date of acquisition			Sep. 06, 2013
Goodwill acquired	$ 3,695	$ 3,733		$ 76
Amount allocated to other intangible assets				$ 75
Other intangible assets useful life, years	10 years 5 months 24 days				9 years 3 months 18 days