Parent and Guarantor Condensed Consolidating Financial Statements (Schedule of Condensed Consolidating Balance Sheet) (Details) - USD ($) $ in Millions	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and Due from Banks	$ 1,514		$ 1,547
Interest-bearing Deposits in Banks and Other Financial Institutions	2,863		4,387
Cash and Cash Equivalents, at Carrying Value	4,377		5,934	$ 5,731		$ 6,380
Trading Securities			0
Available-for-sale securities	21,764		18,926
Held-to-maturity securities	1,189		839
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	17		0
Loans and Leases Receivable, Gross	120,528		118,944	112,653
Loans to bank subsidiary	0		0
Loans to nonbank subsidiary	0		0
Financing Receivable, Allowance for Credit Losses	1,225	$ 1,155	1,144	1,089	$ 1,077	1,054
Loans and Leases Receivable, Net Amount	119,303		117,800
Property Subject to or Available for Operating Lease, Net	9,717		11,470
Receivables from bank subsidiary	0		0
Receivables from nonbank subsidiary	0		0
Investment in bank subsidiaries	0		0
Investment in nonbank subsidiaries	0		0
Premiums receivable and other insurance assets	2,025		1,905
Other Assets	5,953		6,854
Assets	164,345		163,728	157,931
Noninterest-bearing deposit liabilities	107		84
Interest-bearing Deposit Liabilities	86,076		78,938
Deposits	86,183		79,022
Short-term Debt	10,712		12,673
Long-term Debt	49,145		54,128
Debt Payable To Bank Subsidiaries	0		0
Debt Payable To Nonbank Subsidiaries	0		0
Payables to Bank Subsidiaries	0
Payables to Nonbank Subsidiaries	0		0
Interest payable	399		351
Unearned Premiums	2,541		2,500
Accounts Payable and Accrued Liabilities	1,892		1,737
Liabilities	150,872		150,411
Stockholders' Equity Attributable to Parent	13,473		13,317	13,611		13,439
Liabilities and Equity	164,345		163,728
Parent Company [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and Due from Banks	591		720
Interest-bearing Deposits in Banks and Other Financial Institutions	850		100
Cash and Cash Equivalents, at Carrying Value	1,441		820	1,496		1,635
Trading Securities			0
Available-for-sale securities	6		0
Held-to-maturity securities	0		0
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	0
Loans and Leases Receivable, Gross	5,733		4,705
Loans to bank subsidiary	250		1,125
Loans to nonbank subsidiary	833		1,779
Financing Receivable, Allowance for Credit Losses	144		115
Loans and Leases Receivable, Net Amount	6,672		7,494
Property Subject to or Available for Operating Lease, Net	29		42
Receivables from bank subsidiary	85		299
Receivables from nonbank subsidiary	50		107
Investment in bank subsidiaries	18,869		17,727
Investment in nonbank subsidiaries	10,023		10,318
Premiums receivable and other insurance assets	0		0
Other Assets	3,482		4,347
Assets	40,657		41,154
Noninterest-bearing deposit liabilities	0		0
Interest-bearing Deposit Liabilities	45		167
Deposits	45		167
Short-term Debt	4,706		3,622
Long-term Debt	20,755		21,798
Debt Payable To Bank Subsidiaries	95		330
Debt Payable To Nonbank Subsidiaries	937		1,027
Payables to Bank Subsidiaries	1
Payables to Nonbank Subsidiaries	199		153
Interest payable	192		253
Unearned Premiums	0		0
Accounts Payable and Accrued Liabilities	254		487
Liabilities	27,184		27,837
Stockholders' Equity Attributable to Parent	13,473		13,317
Liabilities and Equity	40,657		41,154
Guarantor Subsidiaries [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and Due from Banks	0		0
Interest-bearing Deposits in Banks and Other Financial Institutions	0		0
Cash and Cash Equivalents, at Carrying Value	0		0	0		0
Trading Securities			0
Available-for-sale securities	0		0
Held-to-maturity securities	0		0
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	0
Loans and Leases Receivable, Gross	0		0
Loans to bank subsidiary	0		0
Loans to nonbank subsidiary	0		0
Financing Receivable, Allowance for Credit Losses	0		0
Loans and Leases Receivable, Net Amount	0		0
Property Subject to or Available for Operating Lease, Net	0		0
Receivables from bank subsidiary	0		0
Receivables from nonbank subsidiary	0		0
Investment in bank subsidiaries	18,869		17,727
Investment in nonbank subsidiaries	0		0
Premiums receivable and other insurance assets	0		0
Other Assets	0		0
Assets	18,869		17,727
Noninterest-bearing deposit liabilities	0		0
Interest-bearing Deposit Liabilities	0		0
Deposits	0		0
Short-term Debt	0		0
Long-term Debt	0		0
Debt Payable To Bank Subsidiaries	0		0
Debt Payable To Nonbank Subsidiaries	0		0
Payables to Bank Subsidiaries	0
Payables to Nonbank Subsidiaries	0		0
Interest payable	0		0
Unearned Premiums	0		0
Accounts Payable and Accrued Liabilities	0		0
Liabilities	0		0
Stockholders' Equity Attributable to Parent	18,869		17,727
Liabilities and Equity	18,869		17,727
Non-Guarantor Subsidiaries [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and Due from Banks	923		827
Interest-bearing Deposits in Banks and Other Financial Institutions	2,013		4,287
Cash and Cash Equivalents, at Carrying Value	3,493		5,515	5,074		5,595
Trading Securities			82
Available-for-sale securities	21,764		19,253
Held-to-maturity securities	1,284		839
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	17
Loans and Leases Receivable, Gross	114,795		114,239
Loans to bank subsidiary	0		0
Loans to nonbank subsidiary	380		626
Financing Receivable, Allowance for Credit Losses	1,081		1,029
Loans and Leases Receivable, Net Amount	114,094		113,836
Property Subject to or Available for Operating Lease, Net	9,688		11,428
Receivables from bank subsidiary	0		0
Receivables from nonbank subsidiary	145		67
Investment in bank subsidiaries	0		0
Investment in nonbank subsidiaries	0		0
Premiums receivable and other insurance assets	2,055		1,936
Other Assets	4,684		5,085
Assets	157,224		158,041
Noninterest-bearing deposit liabilities	107		84
Interest-bearing Deposit Liabilities	86,031		78,771
Deposits	86,138		78,855
Short-term Debt	6,006		9,051
Long-term Debt	28,390		32,330
Debt Payable To Bank Subsidiaries	0		0
Debt Payable To Nonbank Subsidiaries	1,089		2,903
Payables to Bank Subsidiaries	0
Payables to Nonbank Subsidiaries	110		351
Interest payable	207		98
Unearned Premiums	2,541		2,500
Accounts Payable and Accrued Liabilities	3,852		3,911
Liabilities	128,333		129,999
Stockholders' Equity Attributable to Parent	28,891		28,042
Liabilities and Equity	157,224		158,041
Affiliated Entity [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Interest-bearing Deposits in Banks and Other Financial Institutions	0		0
Affiliated Entity [Member] | Parent Company [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Interest-bearing Deposits in Banks and Other Financial Institutions	0		0
Affiliated Entity [Member] | Guarantor Subsidiaries [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Interest-bearing Deposits in Banks and Other Financial Institutions	0		0
Affiliated Entity [Member] | Non-Guarantor Subsidiaries [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Interest-bearing Deposits in Banks and Other Financial Institutions	557		401
Consolidation, Eliminations [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and Due from Banks	0		0
Interest-bearing Deposits in Banks and Other Financial Institutions	0		0
Cash and Cash Equivalents, at Carrying Value	(557)		(401)	$ (839)		$ (850)
Trading Securities			(82)
Available-for-sale securities	(6)		(327)
Held-to-maturity securities	(95)		0
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	0
Loans and Leases Receivable, Gross	0		0
Loans to bank subsidiary	(250)		(1,125)
Loans to nonbank subsidiary	(1,213)		(2,405)
Financing Receivable, Allowance for Credit Losses	0		0
Loans and Leases Receivable, Net Amount	(1,463)		(3,530)
Property Subject to or Available for Operating Lease, Net	0		0
Receivables from bank subsidiary	(85)		(299)
Receivables from nonbank subsidiary	(195)		(174)
Investment in bank subsidiaries	(37,738)		(35,454)
Investment in nonbank subsidiaries	(10,023)		(10,318)
Premiums receivable and other insurance assets	(30)		(31)
Other Assets	(2,213)		(2,578)
Assets	(52,405)		(53,194)
Noninterest-bearing deposit liabilities	0		0
Interest-bearing Deposit Liabilities	0		0
Deposits	0		0
Short-term Debt	0		0
Long-term Debt	0		0
Debt Payable To Bank Subsidiaries	(95)		(330)
Debt Payable To Nonbank Subsidiaries	(2,026)		(3,930)
Payables to Bank Subsidiaries	(1)
Payables to Nonbank Subsidiaries	(309)		(504)
Interest payable	0		0
Unearned Premiums	0		0
Accounts Payable and Accrued Liabilities	(2,214)		(2,661)
Liabilities	(4,645)		(7,425)
Stockholders' Equity Attributable to Parent	(47,760)		(45,769)
Liabilities and Equity	(52,405)		(53,194)
Consolidation, Eliminations [Member] | Affiliated Entity [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Interest-bearing Deposits in Banks and Other Financial Institutions	$ (557)		$ (401)