Finance Receivables and Loans, Net (Financing Receivable Credit Quality Indicators) (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	$ 120,528	$ 118,944	$ 112,653
Consumer Portfolio Segment [Member] | Consumer Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	78,068	76,843
Consumer Portfolio Segment [Member] | Consumer Loan [Member] | Performing Financial Instruments [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	77,436	76,146
Consumer Portfolio Segment [Member] | Consumer Loan [Member] | Nonperforming Financial Instruments [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	632	697
Consumer Portfolio Segment [Member] | Automobile Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	66,774	65,793	63,281
Consumer Portfolio Segment [Member] | Automobile Loan [Member] | Performing Financial Instruments [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	66,234	65,195
Consumer Portfolio Segment [Member] | Automobile Loan [Member] | Nonperforming Financial Instruments [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	540	598
Consumer Portfolio Segment [Member] | Residential Mortgage [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	11,294	11,050	$ 11,084
Consumer Portfolio Segment [Member] | Residential Mortgage [Member] | Performing Financial Instruments [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	11,202	10,951
Consumer Portfolio Segment [Member] | Residential Mortgage [Member] | Nonperforming Financial Instruments [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	92	99
Consumer Portfolio Segment [Member] | Mortgage Finance [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	8,866	8,294
Consumer Portfolio Segment [Member] | Mortgage Finance [Member] | Performing Financial Instruments [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	8,857	8,284
Consumer Portfolio Segment [Member] | Mortgage Finance [Member] | Nonperforming Financial Instruments [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	9	10
Consumer Portfolio Segment [Member] | Mortgage - Legacy [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	2,428	2,756
Consumer Portfolio Segment [Member] | Mortgage - Legacy [Member] | Performing Financial Instruments [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	2,345	2,667
Consumer Portfolio Segment [Member] | Mortgage - Legacy [Member] | Nonperforming Financial Instruments [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	$ 83	$ 89