Investment Components, Including Associated Derivatives but Excluding Held to Maturity Investments (Detail) - USD ($)
$ in Millions
Mar. 31, 2016
Dec. 31, 2015
Jun. 30, 2015
Mar. 31, 2015
Dec. 31, 2014
Jun. 30, 2014
Cash, Cash Equivalents and Investments [Line Items]            
Cost Basis $ 112,038   $ 103,647      
Unrealized Gains 5,177   5,220      
Unrealized Losses (373)   (313)      
Recorded Basis 116,842   108,554      
Cash and cash equivalents 7,170 $ 7,185 5,595 $ 7,414 $ 6,426 $ 8,669
Short-term Investments 98,382   90,931      
Equity and Other Investments 11,290   12,028      
Cash            
Cash, Cash Equivalents and Investments [Line Items]            
Cash 3,691   3,679      
Unrealized Gains 0   0      
Unrealized Losses 0   0      
Cash 3,691   3,679      
Cash and cash equivalents 3,691   3,679      
Short-term Investments 0   0      
Equity and Other Investments 0   0      
Mutual funds            
Cash, Cash Equivalents and Investments [Line Items]            
Cost Basis 1,111   1,100      
Unrealized Gains 0   0      
Unrealized Losses 0   0      
Recorded Basis 1,111   1,100      
Cash and cash equivalents 1,111   1,100      
Short-term Investments 0   0      
Equity and Other Investments 0   0      
Commercial paper            
Cash, Cash Equivalents and Investments [Line Items]            
Cost Basis 824   1      
Unrealized Gains 0   0      
Unrealized Losses 0   0      
Recorded Basis 824   1      
Cash and cash equivalents 824   1      
Short-term Investments 0   0      
Equity and Other Investments 0   0      
Certificates of deposit            
Cash, Cash Equivalents and Investments [Line Items]            
Cost Basis 1,324   906      
Unrealized Gains 0   0      
Unrealized Losses 0   0      
Recorded Basis 1,324   906      
Cash and cash equivalents 1,178   776      
Short-term Investments 146   130      
Equity and Other Investments 0   0      
U.S. government and agency securities            
Cash, Cash Equivalents and Investments [Line Items]            
Cost Basis 81,676   72,843      
Unrealized Gains 98   76      
Unrealized Losses (23)   (30)      
Recorded Basis 81,751   72,889      
Cash and cash equivalents 138   39      
Short-term Investments 81,613   72,850      
Equity and Other Investments 0   0      
Foreign government bonds            
Cash, Cash Equivalents and Investments [Line Items]            
Cost Basis 5,221   5,477      
Unrealized Gains 6   3      
Unrealized Losses (28)   (24)      
Recorded Basis 5,199   5,456      
Cash and cash equivalents 228   0      
Short-term Investments 4,971   5,456      
Equity and Other Investments 0   0      
Mortgage- and asset-backed securities            
Cash, Cash Equivalents and Investments [Line Items]            
Cost Basis 4,695   4,899      
Unrealized Gains 19   23      
Unrealized Losses (4)   (6)      
Recorded Basis 4,710   4,916      
Cash and cash equivalents 0   0      
Short-term Investments 4,710   4,916      
Equity and Other Investments 0   0      
Corporate notes and bonds            
Cash, Cash Equivalents and Investments [Line Items]            
Cost Basis 6,582   7,192      
Unrealized Gains 95   97      
Unrealized Losses (64)   (37)      
Recorded Basis 6,613   7,252      
Cash and cash equivalents 0   0      
Short-term Investments 6,613   7,252      
Equity and Other Investments 0   0      
Municipal securities            
Cash, Cash Equivalents and Investments [Line Items]            
Cost Basis 285   285      
Unrealized Gains 47   35      
Unrealized Losses 0   (1)      
Recorded Basis 332   319      
Cash and cash equivalents 0   0      
Short-term Investments 332   319      
Equity and Other Investments 0   0      
Common and preferred stock            
Cash, Cash Equivalents and Investments [Line Items]            
Cost Basis 6,075   6,668      
Unrealized Gains 4,912   4,986      
Unrealized Losses (254)   (215)      
Recorded Basis 10,733   11,439      
Cash and cash equivalents 0   0      
Short-term Investments 0   0      
Equity and Other Investments 10,733   11,439      
Other investments            
Cash, Cash Equivalents and Investments [Line Items]            
Cost Basis 554   597      
Unrealized Gains 0   0      
Unrealized Losses 0   0      
Recorded Basis 554   597      
Cash and cash equivalents 0   0      
Short-term Investments (3)   8      
Equity and Other Investments $ 557   $ 589