Securities - Amortized Cost, Gross Unrealized Gains, Gross Unrealized Losses, and Fair Values of Securities (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Securities available for sale
Amortized Cost	$ 15,686	$ 16,680
Gross Unrealized Gains	128	41
Gross Unrealized Losses	102	407
Securities Available for Sale	15,712	16,314
U.S. Treasury
Securities available for sale
Amortized Cost	2,287	3,572
Gross Unrealized Gains	1	1
Gross Unrealized Losses	25	144
Securities Available for Sale	2,263	3,429
U.S. government agency and government-sponsored agencies
Securities available for sale
Amortized Cost	8,345	8,168
Gross Unrealized Gains	34	7
Gross Unrealized Losses	48	168
Securities Available for Sale	8,331	8,007
Privately issued
Securities available for sale
Amortized Cost	918	887
Gross Unrealized Gains	7	0
Gross Unrealized Losses	4	23
Securities Available for Sale	921	864
Privately issued - commercial mortgage-backed securities
Securities available for sale
Amortized Cost	1,493	1,179
Gross Unrealized Gains	49	3
Gross Unrealized Losses	0	20
Securities Available for Sale	1,542	1,162
Collateralized loan obligations
Securities available for sale
Amortized Cost	1,540	1,492
Gross Unrealized Gains	1	0
Gross Unrealized Losses	6	18
Securities Available for Sale	1,535	1,474
Other
Securities available for sale
Amortized Cost	4	4
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Securities Available for Sale	4	4
Asset Liability Management securities
Securities available for sale
Amortized Cost	14,587	15,302
Gross Unrealized Gains	92	11
Gross Unrealized Losses	83	373
Securities Available for Sale	14,596	14,940
Direct bank purchase bonds
Securities available for sale
Amortized Cost	927	1,190
Gross Unrealized Gains	34	30
Gross Unrealized Losses	18	30
Securities Available for Sale	943	1,190
Other
Securities available for sale
Amortized Cost	172	188
Gross Unrealized Gains	2	0
Gross Unrealized Losses	1	4
Securities Available for Sale	$ 173	$ 184

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

No definition available.

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- Definition

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563

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- Definition

Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

No definition available.

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- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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