Investment Securities (Details 2) $ in Millions	Jun. 30, 2019 USD ($) security	Dec. 31, 2018 USD ($) security
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Number of Positions [Abstract]
Number of securities, less than 12 months \| security	0	2
Number of securities, 12 months or more \| security	7	29
Number of securities, total \| security	7	31
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Estimated Fair Value, Less than 12 months	$ 0	$ 224
Estimated Fair Value, 12 months or more	477	873
Estimated Fair Value, Total	477	1,097
Available For Sale Securities Continuous Unrealized Aggregate Losses [Abstract]
Gross Unrealized Losses, Less than 12 Months	0	(2)
Gross Unrealized Losses, 12 months or more	(3)	(16)
Gross Unrealized Losses, Total	$ (3)	$ (18)
Ratio Of Fair Value To Amortized Cost Between Ninety And One Hundred Percent [Member]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Number of Positions [Abstract]
Number of securities, less than 12 months \| security	0	2
Number of securities, 12 months or more \| security	7	29
Number of securities, total \| security	7	31
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Estimated Fair Value, Less than 12 months	$ 0	$ 224
Estimated Fair Value, 12 months or more	477	873
Estimated Fair Value, Total	477	1,097
Available For Sale Securities Continuous Unrealized Aggregate Losses [Abstract]
Gross Unrealized Losses, Less than 12 Months	0	(2)
Gross Unrealized Losses, 12 months or more	(3)	(16)
Gross Unrealized Losses, Total	$ (3)	$ (18)

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Number of investments in debt securities measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer, without an allowance for credit loss. Includes beneficial interest in securitized financial asset.

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