Fair Value Measurement and Fair Value of Financial Instruments (Details 5) - USD ($) $ in Millions		Jun. 30, 2016	Dec. 31, 2015
Assets
Fair value of securities held to maturity		$ 10,573	$ 10,207
Level 1
Assets
Cash and cash equivalents		3,865	4,529
Level 2
Assets
Fair value of securities held to maturity		10,573	10,207
Liabilities
Deposits		82,739	84,375
Commercial paper and other short-term borrowings		4,703	1,038
Long-term debt		10,523	12,351
Level 3
Assets
Loans held for investment, net of allowance for loan losses	[1]	79,833	77,640
Other assets			17
Off-Balance Sheet Instruments
Commitments to extend credit and standby and commercial letters of credit		238	243
Carrying Amount
Assets
Cash and cash equivalents		3,865	4,529
Fair value of securities held to maturity		10,259	10,158
Loans held for investment, net of allowance for loan losses	[1]	77,931	76,150
Other assets			16
Liabilities
Deposits		82,692	84,340
Commercial paper and other short-term borrowings		4,703	1,038
Long-term debt		10,445	12,349
Off-Balance Sheet Instruments
Commitments to extend credit and standby and commercial letters of credit		238	243
Fair Value
Assets
Cash and cash equivalents		3,865	4,529
Fair value of securities held to maturity		10,573	10,207
Loans held for investment, net of allowance for loan losses		79,833	77,640
Other assets			17
Liabilities
Deposits		82,739	84,375
Commercial paper and other short-term borrowings		4,703	1,038
Long-term debt		10,523	12,351
Off-Balance Sheet Instruments
Commitments to extend credit and standby and commercial letters of credit		$ 238	$ 243

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