Fair Value Election and Measurement Level 3 Significant Unobservable Input Assumptions (Details) $ in Millions		Sep. 30, 2018 USD ($)		Dec. 31, 2017 USD ($)
level 3 fair value assumptions [Line Items]
Available-for-sale Securities	[1],[2]	$ 30,984		$ 30,947	[3]
Loans Receivable, Fair Value Disclosure		168		196
Fair Value, Inputs, Level 3 [Member]
level 3 fair value assumptions [Line Items]
Available-for-sale Securities		0		72
Loans Receivable, Fair Value Disclosure		168		196
Fair Value, Measurements, Recurring [Member]
level 3 fair value assumptions [Line Items]
Available-for-sale Securities		30,984	[4]	30,947	[5]
Loans Receivable, Fair Value Disclosure		168		196
Servicing Asset at Fair Value, Amount		2,062		1,710
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
level 3 fair value assumptions [Line Items]
Available-for-sale Securities		0	[4]	72	[5]
Loans Receivable, Fair Value Disclosure		168		196
Servicing Asset at Fair Value, Amount		2,062		1,710
Fair Value, Measurements, Recurring [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member]
level 3 fair value assumptions [Line Items]
Derivative, Fair Value, Net		3	[6]	0	[7]
Loans Receivable, Fair Value Disclosure		6		4
Fair Value, Measurements, Recurring [Member] | Valuation, Income Approach [Member] | Fair Value, Inputs, Level 3 [Member]
level 3 fair value assumptions [Line Items]
Loans Receivable, Fair Value Disclosure		162		192
Servicing Asset at Fair Value, Amount		$ 2,062		1,710
Fair Value, Measurements, Recurring [Member] | Asset-backed Securities [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member]
level 3 fair value assumptions [Line Items]
Available-for-sale Securities				8
Fair Value, Measurements, Recurring [Member] | Other Debt Obligations [Member] | Valuation, Cost Approach [Member] | Fair Value, Inputs, Level 3 [Member]
level 3 fair value assumptions [Line Items]
Available-for-sale Securities				5
Fair Value, Measurements, Recurring [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member] | Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member]
level 3 fair value assumptions [Line Items]
Available-for-sale Securities				$ 59
Pull Through Rate [Member] | Fair Value, Measurements, Recurring [Member] | Valuation, Market Approach [Member] | Minimum [Member] | Fair Value, Inputs, Level 3 [Member]
level 3 fair value assumptions [Line Items]
Derivative Asset (Liability) Net, Measurement Input		0.40		0.41
Pull Through Rate [Member] | Fair Value, Measurements, Recurring [Member] | Valuation, Market Approach [Member] | Maximum [Member] | Fair Value, Inputs, Level 3 [Member]
level 3 fair value assumptions [Line Items]
Derivative Asset (Liability) Net, Measurement Input		1.00		1.00
Pull Through Rate [Member] | Fair Value, Measurements, Recurring [Member] | Valuation, Market Approach [Member] | Weighted Average [Member] | Fair Value, Inputs, Level 3 [Member]
level 3 fair value assumptions [Line Items]
Derivative Asset (Liability) Net, Measurement Input		0.82		0.81
MSR Value [Member] | Fair Value, Measurements, Recurring [Member] | Valuation, Market Approach [Member] | Minimum [Member] | Fair Value, Inputs, Level 3 [Member]
level 3 fair value assumptions [Line Items]
Derivative Asset (Liability) Net, Measurement Input		0.0028		0.0041
MSR Value [Member] | Fair Value, Measurements, Recurring [Member] | Valuation, Market Approach [Member] | Maximum [Member] | Fair Value, Inputs, Level 3 [Member]
level 3 fair value assumptions [Line Items]
Derivative Asset (Liability) Net, Measurement Input		0.0173		0.0190
MSR Value [Member] | Fair Value, Measurements, Recurring [Member] | Valuation, Market Approach [Member] | Weighted Average [Member] | Fair Value, Inputs, Level 3 [Member]
level 3 fair value assumptions [Line Items]
Derivative Asset (Liability) Net, Measurement Input		0.0116		0.0113
Measurement Input, Credit Spread [Member] | Fair Value, Measurements, Recurring [Member] | Valuation, Income Approach [Member] | Minimum [Member] | Fair Value, Inputs, Level 3 [Member]
level 3 fair value assumptions [Line Items]
Loans Held-For-Investment, Measurement Input		0.0062		0.0062
Servicing Asset, Measurement Input		0.00		0.01
Measurement Input, Credit Spread [Member] | Fair Value, Measurements, Recurring [Member] | Valuation, Income Approach [Member] | Maximum [Member] | Fair Value, Inputs, Level 3 [Member]
level 3 fair value assumptions [Line Items]
Loans Held-For-Investment, Measurement Input		0.0784		0.0784
Servicing Asset, Measurement Input		1.13		1.25
Measurement Input, Credit Spread [Member] | Fair Value, Measurements, Recurring [Member] | Valuation, Income Approach [Member] | Weighted Average [Member] | Fair Value, Inputs, Level 3 [Member]
level 3 fair value assumptions [Line Items]
Loans Held-For-Investment, Measurement Input		0.0177		0.0215
Servicing Asset, Measurement Input		0.03		0.04
Measurement Input, Prepayment Rate [Member] | Fair Value, Measurements, Recurring [Member] | Valuation, Income Approach [Member] | Minimum [Member] | Fair Value, Inputs, Level 3 [Member]
level 3 fair value assumptions [Line Items]
Loans Held-For-Investment, Measurement Input		0.04		0.02
Servicing Asset, Measurement Input		0.05		0.06
Measurement Input, Prepayment Rate [Member] | Fair Value, Measurements, Recurring [Member] | Valuation, Income Approach [Member] | Maximum [Member] | Fair Value, Inputs, Level 3 [Member]
level 3 fair value assumptions [Line Items]
Loans Held-For-Investment, Measurement Input		0.27		0.34
Servicing Asset, Measurement Input		0.30		0.30
Measurement Input, Prepayment Rate [Member] | Fair Value, Measurements, Recurring [Member] | Valuation, Income Approach [Member] | Weighted Average [Member] | Fair Value, Inputs, Level 3 [Member]
level 3 fair value assumptions [Line Items]
Loans Held-For-Investment, Measurement Input		0.12		0.11
Servicing Asset, Measurement Input		0.13		0.13
Measurement Input, Default Rate [Member] | Fair Value, Measurements, Recurring [Member] | Valuation, Income Approach [Member] | Minimum [Member] | Fair Value, Inputs, Level 3 [Member]
level 3 fair value assumptions [Line Items]
Loans Held-For-Investment, Measurement Input		0.00		0.00
Measurement Input, Default Rate [Member] | Fair Value, Measurements, Recurring [Member] | Valuation, Income Approach [Member] | Maximum [Member] | Fair Value, Inputs, Level 3 [Member]
level 3 fair value assumptions [Line Items]
Loans Held-For-Investment, Measurement Input		0.02		0.05
Measurement Input, Default Rate [Member] | Fair Value, Measurements, Recurring [Member] | Valuation, Income Approach [Member] | Weighted Average [Member] | Fair Value, Inputs, Level 3 [Member]
level 3 fair value assumptions [Line Items]
Loans Held-For-Investment, Measurement Input		0.007		0.007

[1] Beginning January 1, 2018, the Company reclassified equity securities previously presented in Securities available for sale to Other assets. Reclassifications have been made to previously reported amounts for comparability.

[2] Includes securities AFS pledged as collateral where counterparties have the right to sell or repledge the collateral of $164 million and $223 million at September 30, 2018 and December 31, 2017, respectively.

[3] Beginning January 1, 2018, the Company reclassified equity securities previously presented in Securities available for sale to Other assets on the Consolidated Balance Sheets. Reclassifications have been made to previously reported amounts for comparability. See Note 9, "Other Assets," for additional information.

[4] Beginning January 1, 2018, the Company reclassified equity securities previously presented in Securities available for sale to Other assets on the Consolidated Balance Sheets. Reclassifications have been made to previously reported amounts for comparability. See Note 9, "Other Assets," for additional information.

[5] Beginning January 1, 2018, the Company reclassified equity securities previously presented in Securities available for sale to Other assets on the Consolidated Balance Sheets. Reclassifications have been made to previously reported amounts for comparability. See Note 9, "Other Assets," for additional information.

[6] Amount represents the net of IRLC assets and liabilities and includes the derivative liability associated with the Company's sale of Visa shares. Refer to the "Trading Liabilities and Derivative Instruments" section herein for a discussion of valuation assumptions related to the Visa derivative liability.

[7] Amount represents the net of IRLC assets and liabilities and includes the derivative liability associated with the Company's sale of Visa shares. Refer to the "Trading Liabilities and Derivative Instruments" section herein for a discussion of valuation assumptions related to the Visa derivative liability.