Derivative Instruments and Hedging Activities (Schedule of Fair Value Hedging Instruments, Statements of Financial Performance and Financial Position, Location) (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Hedged Asset, Discontinued Fair Value Hedge, Last-of-Layer, Amount	$ 12,800
Basis adjustment, last of layer hedging relationship		$ 0
Available-for-sale securities
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Hedged Asset, Fair Value Hedge	1,401	1,485
Cumulative basis adjustments for fair value hedges included in the carrying amount of hedged items	(11)	0
Amortized cost basis of the closed portfolios used in hedging relationships		47
Hedged asset, last-of-layer, amount		28
Finance receivables and loans, net
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Hedged Asset, Fair Value Hedge	46,111	40,850
Cumulative basis adjustments for fair value hedges included in the carrying amount of hedged items	(153)	(24)
Hedged asset, discontinued fair value hedge, cumulative increase (decrease)	57
Hedged asset, last-of-layer, amount	13,400	21,400
Hedge basis adjustment, last-of-layer		19
Long-term debt
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Hedged Liability, Fair Value Hedge	12,093	13,001
Hedged Liability, Fair Value Hedge, Cumulative Increase (Decrease)	85	67
Fair Value Hedging | Finance receivables and loans, net
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Cumulative basis adjustments for fair value hedges included in the carrying amount of hedged items	(94)
Discontinued hedge | Available-for-sale securities
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Hedged asset, discontinued fair value hedge, cumulative increase (decrease)	10	(5)
Discontinued hedge | Finance receivables and loans, net
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Hedged asset, discontinued fair value hedge, cumulative increase (decrease)	59	5
Discontinued hedge | Long-term debt
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Hedged Liability, Fair Value Hedge, Cumulative Increase (Decrease)	$ 66	$ 67