Statements of Cash Flow - Parent Company Only (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net Income (Loss) Attributable to Parent		$ 1,878	$ 1,933	$ 1,774
Gain (Loss) on Disposition of Business		0	0	(105)
Depreciation, Amortization and Accretion, Net		725	786	693
Deferred Income Tax Expense (Benefit)		111	21	99
Stock Option Compensation And Amortization Of Restricted Stock Compensation		126	89	67
Gain (Loss) on Sale of Securities, Net		(4)	(21)	15
Increase (Decrease) in Other Operating Assets	[1]	(800)	(407)	(45)
Increase (Decrease) in Other Operating Liabilities	[1]	(274)	(166)	(416)
Net Cash Provided by (Used in) Operating Activities, Continuing Operations		(681)	3,552	(1,160)
Proceeds from Maturities, Prepayments and Calls of Available-for-sale Securities		5,108	5,680	4,707
Proceeds from Sale of Available-for-sale Securities		197	2,708	2,470
Payments to Acquire Available-for-sale Securities		(8,610)	(9,882)	(11,039)
Proceeds from sales of auction rate securities		0	0	59
Proceeds from Divestiture of Businesses		0	0	193
Net Cash Provided by (Used in) Investing Activities, Continuing Operations		(11,157)	(5,316)	(9,273)
Proceeds from Issuance of Long-term Debt		6,705	1,351	2,574
Repayments of Long-term Debt		(3,231)	(5,684)	(53)
Proceeds from Issuance of Preferred Stock and Preference Stock		0	0	496
Payments for Repurchase of Common Stock		(806)	(679)	(458)
Payments for Repurchase of Warrants		(24)	0	0
Payments Related to Tax Withholding for Share-based Compensation	[1]	(48)	(36)	(16)
Proceeds from the exercise of stock options	[1]	25	17	10
Net Cash Provided by (Used in) Financing Activities, Continuing Operations		12,662	(866)	13,399
Cash and Cash Equivalents, Period Increase (Decrease)		824	(2,630)	2,966
Cash and cash equivalents		6,423	5,599	8,229	$ 5,263
Income Taxes Paid		813	497	380
Interest Paid		559	523	534
Parent Company [Member]
Net Income (Loss) Attributable to Parent		1,878	1,933	1,774
Gain (Loss) on Disposition of Business		0	0	(105)
Equity in Undistributed Earnings of Subsidiaries		(725)	(916)	(772)
Depreciation, Amortization and Accretion, Net		3	6	5
Deferred Income Tax Expense (Benefit)		11	(4)	35
Stock Option Compensation And Amortization Of Restricted Stock Compensation		3	11	21
Gain (Loss) on Sale of Securities, Net		0	0	2
Increase (Decrease) in Other Operating Assets	[2]	(129)	(72)	207
Increase (Decrease) in Other Operating Liabilities	[2]	62	(28)	29
Net Cash Provided by (Used in) Operating Activities, Continuing Operations		1,103	930	1,196
Proceeds from Maturities, Prepayments and Calls of Available-for-sale Securities		49	66	71
Proceeds from Sale of Available-for-sale Securities		4	0	21
Payments to Acquire Available-for-sale Securities		(4)	(15)	(26)
Proceeds from sales of auction rate securities		0	0	59
Payments for (Proceeds from) Loans Receivable		(889)	1,042	(1,518)
Proceeds from Divestiture of Businesses		0	0	193
Proceeds from Contributions from Affiliates		0	0	(32)
Payments for (Proceeds from) Other Investing Activities		(3)	(2)	(10)
Net Cash Provided by (Used in) Investing Activities, Continuing Operations		(843)	1,091	(1,242)
Proceeds from (Repayments of) Short-term Debt		5	(763)	(686)
Proceeds from Issuance of Long-term Debt		2,005	0	723
Repayments of Long-term Debt		(1,784)	(29)	(5)
Proceeds from Issuance of Preferred Stock and Preference Stock		0	0	496
Payments for Repurchase of Common Stock		(806)	(679)	(458)
Payments for Repurchase of Warrants		(24)	0	0
Payments of Dividends		(564)	(539)	(409)
Payments Related to Tax Withholding for Share-based Compensation	[2]	(48)	(36)	(16)
Proceeds from the exercise of stock options	[2]	25	17	10
Net Cash Provided by (Used in) Financing Activities, Continuing Operations		(1,191)	(2,029)	(345)
Cash and Cash Equivalents, Period Increase (Decrease)		(931)	(8)	(391)
Cash and cash equivalents		1,684	2,615	2,623	$ 3,014
Income Taxes Paid		(886)	(499)	(219)
Income Taxes Received From (Paid To) Subsidiaries		812	481	171
Income Taxes Paid, Net		(74)	(18)	(48)
Interest Paid		$ 135	$ 130	$ 131

[1] Related to the Company's early adoption of ASU 2016-09, certain prior period amounts have been retrospectively reclassified between operating activities and financing activities. See Note 1, "Significant Accounting Policies," for additional information.

[2] 1 Related to the Company's early adoption of ASU 2016-09, certain prior period amounts have been retrospectively reclassified between operating activities and financing activities. See Note 1, "Significant Accounting Policies," for additional information.