Parent and Guarantor Consolidating Financial Statements (Schedule of Condensed Consolidating Balance Sheet) (Details) - USD ($) $ in Millions	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2014
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and Due from Banks	$ 1,779		$ 2,148
Interest-bearing Deposits in Banks and Other Financial Institutions	2,510		4,232
Cash and Cash Equivalents, at Carrying Value	4,289		6,380	$ 5,227		$ 5,576
Available-for-sale securities	17,701		17,157
Held-to-maturity securities	649		0
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	56		105
Loans and Leases Receivable, Gross	114,959		111,600	107,990
Loans to bank subsidiary	0		0
Loans to nonbank subsidiary	0		0
Loans and Leases Receivable, Allowance	(1,134)	$ (1,089)	(1,054)	(1,018)	$ (974)	(977)
Loans and Leases Receivable, Net Amount	113,825		110,546
Property Subject to or Available for Operating Lease, Net	12,689		16,271
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	1,881		1,801
Other assets	6,307		6,321
Assets	157,397		158,581	155,916
Noninterest-bearing deposit liabilities	101		89
Interest-bearing deposit liabilities	75,643		66,389
Deposits	75,744		66,478
Short-term Debt	6,434		8,101
Long-term debt	56,836		66,234
Debt Payable To Bank Subsidiaries	0
Debt Payable To Nonbank Subsidiaries	0		0
Payables to Bank Subsidiaries	0		0
Payables to Nonbank Subsidiaries	0		0
Interest payable	462		350
Unearned Premiums	2,493		2,434
Accounts Payable and Accrued Liabilities	1,798		1,545
Liabilities	143,767		145,142
Stockholders' Equity Attributable to Parent, Total	13,630		13,439	14,599		15,399
Liabilities and Equity	157,397		158,581
Parent Company [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and Due from Banks	809		1,234
Interest-bearing Deposits in Banks and Other Financial Institutions	600		401
Cash and Cash Equivalents, at Carrying Value	1,409		1,635	1,998		2,286
Available-for-sale securities	0		0
Held-to-maturity securities	0
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	0		0
Loans and Leases Receivable, Gross	5,501		2,636
Loans to bank subsidiary	300		600
Loans to nonbank subsidiary	1,693		3,277
Loans and Leases Receivable, Allowance	(125)		(72)
Loans and Leases Receivable, Net Amount	7,369		6,441
Property Subject to or Available for Operating Lease, Net	50		81
Receivables from bank subsidiary	343		186
Receivables from nonbank subsidiary	90		259
Investment in bank subsidiaries	17,582		16,496
Investment in nonbank subsidiaries	11,378		10,902
Premiums receivable and other insurance assets	0		0
Other assets	4,434		4,785
Assets	42,655		40,785
Noninterest-bearing deposit liabilities	0		0
Interest-bearing deposit liabilities	193		229
Deposits	193		229
Short-term Debt	3,525		3,453
Long-term debt	22,264		21,048
Debt Payable To Bank Subsidiaries	330
Debt Payable To Nonbank Subsidiaries	1,379		1,409
Payables to Bank Subsidiaries	436		142
Payables to Nonbank Subsidiaries	179		420
Interest payable	247		258
Unearned Premiums	0		0
Accounts Payable and Accrued Liabilities	472		387
Liabilities	29,025		27,346
Stockholders' Equity Attributable to Parent, Total	13,630		13,439
Liabilities and Equity	42,655		40,785
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
Available-for-sale securities	0		0
Held-to-maturity securities	0
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	0		0
Loans and Leases Receivable, Gross	0		0
Loans to bank subsidiary	0		0
Loans to nonbank subsidiary	0		0
Loans and Leases Receivable, Allowance	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	17,582		16,496
Investment in nonbank subsidiaries	1		11
Premiums receivable and other insurance assets	0		0
Other assets	0		0
Assets	17,583		16,507
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
Debt Payable To Nonbank Subsidiaries	0		0
Payables to Bank Subsidiaries	0		0
Payables to Nonbank Subsidiaries	0		0
Interest payable	0		0
Unearned Premiums	0		0
Accounts Payable and Accrued Liabilities	0		82
Liabilities	0		82
Stockholders' Equity Attributable to Parent, Total	17,583		16,425
Liabilities and Equity	17,583		16,507
Non-Guarantor Subsidiaries [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and Due from Banks	970		914
Interest-bearing Deposits in Banks and Other Financial Institutions	1,910		3,831
Cash and Cash Equivalents, at Carrying Value	3,659		5,595	3,951		3,905
Available-for-sale securities	18,030		17,157
Held-to-maturity securities	649
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	56		105
Loans and Leases Receivable, Gross	109,458		108,964
Loans to bank subsidiary	0		0
Loans to nonbank subsidiary	600		559
Loans and Leases Receivable, Allowance	(1,009)		(982)
Loans and Leases Receivable, Net Amount	109,049		108,541
Property Subject to or Available for Operating Lease, Net	12,639		16,190
Receivables from bank subsidiary	0		0
Receivables from nonbank subsidiary	127		282
Investment in bank subsidiaries	0		0
Investment in nonbank subsidiaries	0		0
Premiums receivable and other insurance assets	1,906		1,827
Other assets	4,681		4,488
Assets	150,796		154,185
Noninterest-bearing deposit liabilities	101		89
Interest-bearing deposit liabilities	75,450		66,160
Deposits	75,551		66,249
Short-term Debt	2,909		4,648
Long-term debt	34,572		45,186
Debt Payable To Bank Subsidiaries	0
Debt Payable To Nonbank Subsidiaries	1,993		3,877
Payables to Bank Subsidiaries	0		0
Payables to Nonbank Subsidiaries	(29)		191
Interest payable	215		92
Unearned Premiums	2,493		2,434
Accounts Payable and Accrued Liabilities	4,133		4,028
Liabilities	121,837		126,705
Stockholders' Equity Attributable to Parent, Total	28,959		27,480
Liabilities and Equity	150,796		154,185
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	779		850
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	(779)		(850)	$ (722)		$ (615)
Available-for-sale securities	(329)		0
Held-to-maturity securities	0
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	0		0
Loans and Leases Receivable, Gross	0		0
Loans to bank subsidiary	(300)		(600)
Loans to nonbank subsidiary	(2,293)		(3,836)
Loans and Leases Receivable, Allowance	0		0
Loans and Leases Receivable, Net Amount	(2,593)		(4,436)
Property Subject to or Available for Operating Lease, Net	0		0
Receivables from bank subsidiary	(343)		(186)
Receivables from nonbank subsidiary	(217)		(541)
Investment in bank subsidiaries	(35,164)		(32,992)
Investment in nonbank subsidiaries	(11,379)		(10,913)
Premiums receivable and other insurance assets	(25)		(26)
Other assets	(2,808)		(2,952)
Assets	(53,637)		(52,896)
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	(330)
Debt Payable To Nonbank Subsidiaries	(3,372)		(5,286)
Payables to Bank Subsidiaries	(436)		(142)
Payables to Nonbank Subsidiaries	(150)		(611)
Interest payable	0		0
Unearned Premiums	0		0
Accounts Payable and Accrued Liabilities	(2,807)		(2,952)
Liabilities	(7,095)		(8,991)
Stockholders' Equity Attributable to Parent, Total	(46,542)		(43,905)
Liabilities and Equity	(53,637)		(52,896)
Consolidation, Eliminations [Member] | Affiliated Entity [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Interest-bearing Deposits in Banks and Other Financial Institutions	$ (779)		$ (850)