Stock Plans - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		9 Months Ended		12 Months Ended		33 Months Ended
	Jul. 29, 2015	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013	Sep. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cost of shares repurchased		$ 3,084		$ 1,891
Payment for repurchase of common stock		$ 3,003	$ 1,020
Common Class A
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock repurchase expiration date		Dec. 31, 2016
Stock repurchase value					$ 7,700
Number of shares repurchased		79.7
Average cost of shares repurchased		$ 38.69
Cost of shares repurchased		$ 3,100		$ 1,900	$ 2,700	$ 7,700
Payment for repurchase of common stock		3,000
Stock repurchase remaining amount		$ 6,000				$ 6,000
Common Class A | Share Repurchase Program amended July 29, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock repurchase expiration date	Dec. 31, 2018
Stock repurchase value	$ 13,700
Increase in share repurchase value	$ 6,000