Fair Value Measurements - Schedule of activity in assets and liabilities classified within Level Three of the valuation hierarchy (Details) - Level Three - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
IRLCs, net
Activity in assets classified within Level Three of the valuation hierarchy
Balance, beginning of period	$ 18	$ 21
Purchases, Issuances, Sales and Settlements:
Purchases	0	0
Issuances	0	0
Sales	0	0
Settlements	(213)	(318)
Purchases, Issuances, Sales and Settlements Total	(213)	(318)
Realized and unrealized gains (losses) included in:
Realized and unrealized gains (losses)	200	315
Transfers into Level Three	0	0
Transfers out of Level Three	0	0
Balance, end of period	5	18
MLHS
Activity in assets classified within Level Three of the valuation hierarchy
Balance, beginning of period	47	39
Purchases, Issuances, Sales and Settlements:
Purchases	7	13
Issuances	5	6
Sales	(59)	(24)
Settlements	(12)	(11)
Purchases, Issuances, Sales and Settlements Total	(59)	(16)
Realized and unrealized gains (losses) included in:
Realized and unrealized gains (losses)	(3)	2
Transfers into Level Three	41	42
Transfers out of Level Three	(17)	(20)
Balance, end of period	9	47
MSRs
Activity in assets classified within Level Three of the valuation hierarchy
Balance, beginning of period	690	880
Purchases, Issuances, Sales and Settlements:
Purchases	0	0
Issuances	36	60
Sales	(131)	(12)
Settlements	0	0
Purchases, Issuances, Sales and Settlements Total	(95)	48
Realized and unrealized gains (losses) included in:
Realized and unrealized gains (losses)	(119)	(238)
Transfers into Level Three	0	0
Transfers out of Level Three	0	0
Balance, end of period	476	690
Gain on loans held for sale, net \| IRLCs, net
Realized and unrealized gains (losses) included in:
Realized and unrealized gains (losses)	200	315
Gain on loans held for sale, net \| MLHS
Realized and unrealized gains (losses) included in:
Realized and unrealized gains (losses)	(3)	(1)
Gain on loans held for sale, net \| MSRs
Realized and unrealized gains (losses) included in:
Realized and unrealized gains (losses)	0	0
Change in fair value of MSRs \| IRLCs, net
Realized and unrealized gains (losses) included in:
Realized and unrealized gains (losses)	0	0
Change in fair value of MSRs \| MLHS
Realized and unrealized gains (losses) included in:
Realized and unrealized gains (losses)	0	0
Change in fair value of MSRs \| MSRs
Realized and unrealized gains (losses) included in:
Realized and unrealized gains (losses)	(119)	(238)
Interest income \| IRLCs, net
Realized and unrealized gains (losses) included in:
Realized and unrealized gains (losses)	0	0
Interest income \| MLHS
Realized and unrealized gains (losses) included in:
Realized and unrealized gains (losses)	0	3
Interest income \| MSRs
Realized and unrealized gains (losses) included in:
Realized and unrealized gains (losses)	0	0
MSRs Secured Liability
Activity in assets classified within Level Three of the valuation hierarchy
Balance, beginning of period	0
Purchases, Issuances, Sales and Settlements:
Purchases	0
Issuances	(467)
Sales	0
Settlements	29
Purchases, Issuances, Sales and Settlements Total	(438)
Realized and unrealized gains (losses) included in:
Realized and unrealized gains (losses)	19
Transfers into Level Three	0
Transfers out of Level Three	0
Balance, end of period	(419)	0
MSRs Secured Liability \| Gain on loans held for sale, net
Realized and unrealized gains (losses) included in:
Realized and unrealized gains (losses)	0
MSRs Secured Liability \| Change in fair value of MSRs
Realized and unrealized gains (losses) included in:
Realized and unrealized gains (losses)	48
MSRs Secured Liability \| Interest income
Realized and unrealized gains (losses) included in:
Realized and unrealized gains (losses)	(29)
Liability to Deliver MSRs
Activity in assets classified within Level Three of the valuation hierarchy
Balance, beginning of period	0
Purchases, Issuances, Sales and Settlements:
Purchases	0
Issuances	0
Sales	0
Settlements	3
Purchases, Issuances, Sales and Settlements Total	3
Realized and unrealized gains (losses) included in:
Realized and unrealized gains (losses)	(5)
Transfers into Level Three	0
Transfers out of Level Three	0
Balance, end of period	(2)	$ 0
Liability to Deliver MSRs \| Gain on loans held for sale, net
Realized and unrealized gains (losses) included in:
Realized and unrealized gains (losses)	(5)
Liability to Deliver MSRs \| Change in fair value of MSRs
Realized and unrealized gains (losses) included in:
Realized and unrealized gains (losses)	0
Liability to Deliver MSRs \| Interest income
Realized and unrealized gains (losses) included in:
Realized and unrealized gains (losses)	$ 0

Fair Value, Realized and Unrealized Gains (Losses) Included in Level 3 of Valuation Hierarchy [Abstract]

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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- Definition

Amount of gain (loss) recognized in the income statement for financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)
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- Definition

Amount of issuances of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
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- Definition

Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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-Publisher FASB
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- Definition

Amount of purchases, (sales), issuances and (settlements) of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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- Definition

Amount of sale of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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-Publisher FASB
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- Definition

Amount of settlement of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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- Definition

Amount of transfer of financial instrument classified as an asset into level 3 of the fair value hierarchy.

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-Name Accounting Standards Codification
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- Definition

Amount of transfers of financial instrument classified as an asset out of level 3 of the fair value hierarchy.

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- Definition

Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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