Derivative Instruments and Hedging Activities - Hedged Items in Fair Value Hedging Relationship (Details) $ in Millions	Jun. 30, 2018 USD ($)
Available-for-sale Securities [Member]
hedged items in fair value hedging relationship [Line Items]
Carry amount of assets	$ 18,425
Hedged Asset Fair Value Hedge Cumulative Increase Decrease	(193)
Hedged Asset Discontinued Fair Value Hedge Cumulative Increase Decrease	0
Interest-bearing Deposits [Member]
hedged items in fair value hedging relationship [Line Items]
Carry amount of liabilities	(14,140)
Hedged Liability Fair Value Hedge Cumulative Increase Decrease	383
Hedged Liability Discontinued Fair Value Hedge Cumulative Increase Decrease	0
Securitized Debt Obligations [Member]
hedged items in fair value hedging relationship [Line Items]
Carry amount of liabilities	(11,890)
Hedged Liability Fair Value Hedge Cumulative Increase Decrease	242
Hedged Liability Discontinued Fair Value Hedge Cumulative Increase Decrease	0
Senior And Subordinated Notes [Member]
hedged items in fair value hedging relationship [Line Items]
Carry amount of liabilities	(29,274)
Hedged Liability Fair Value Hedge Cumulative Increase Decrease	664
Hedged Liability Discontinued Fair Value Hedge Cumulative Increase Decrease	356
Available-for-sale Securities [Member]
hedged items in fair value hedging relationship [Line Items]
Amortized cost of closed prepayment assets	10,300
Amortized cost of closed prepayable assets designated in fair value hedges	4,100
Hedged LOLA assets Cumulative Basis Adjustment	$ (31)

Amortized cost of closed prepayable assets designated in fair value hedges

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- Definition

Amortized cost of closed prepayment assets for LOLA hedging purpose

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No definition available.

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- Definition

Carry amount of assets hedged in fair value hedging relationship

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No definition available.

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- Definition

The carry amount of liabilities in fair value hedging relationship

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No definition available.

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- Definition

Amount of cumulative increase (decrease) in fair value of hedged asset in fair value hedge, attributable to hedged risk, remaining after discontinued hedge

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No definition available.

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- Definition

Amount of cumulative increase (decrease) in fair value of hedged asset in fair value hedge, attributable to hedged risk

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No definition available.

+ Details

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- Definition

Hedged Assets Fair Value Hedge Cumulative Increase Decrease - LOLA

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No definition available.

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- Definition

Amount of cumulative increase (decrease) in fair value of hedged liability in fair value hedge, attributable to hedged risk, remaining after discontinued hedge

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No definition available.

+ Details

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- Definition

Amount of cumulative Increase (Decrease) in fair value of hedged liability in fair value hedge, attributable to hedged risk

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No definition available.

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- Definition

[Line Items] for Table shows the carrying amount and associated cumulative basis adjustment related to the application of hedge accounting that is included in the carrying amount of hedged assets and liabilities in fair value hedging relationships.

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No definition available.

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