Investment Securities (Details 3) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Estimated Fair Value
Estimated Fair Value, Due within 1 year	$ 6,607
Estimated Fair Value, Due after 1 year but within 5 years	1,332
Estimated Fair Value, Due after 5 years but within 10 years	171
Estimated Fair Value, Due after 10 years	218
Total	8,328	$ 4,599
Available For Sale Securities Debt Maturities Amortized Cost [Abstract]
Due within 1 year	6,602
Due after 1 year but within 5 years	1,307
Due after 5 years but within 10 years	166
Due after 10 years	209
Available-for-sale debt securities, Cost	$ 8,284
Weighted average yields
Weighted average yields, due within 1 year	2.17%
Weighted averge yields, due after 1 years but within 5 years	2.27%
Weighted averge yields, due after 5 years but within 10 years	3.01%
Weighted average yield, due after 10 years	3.99%
Weighted average yields, Total	2.25%
State and municipal obligations [Member]
Estimated Fair Value
Estimated Fair Value, Due within 1 year	$ 6
Estimated Fair Value, Due after 1 year but within 5 years	39
Estimated Fair Value, Due after 5 years but within 10 years	30
Estimated Fair Value, Due after 10 years	168
Total	243	596	$ 1,377
Available For Sale Securities Debt Maturities Amortized Cost [Abstract]
Available-for-sale debt securities, Cost	236	594	1,369
US Government agencies obligations [Member]
Estimated Fair Value
Estimated Fair Value, Due within 1 year	0
Estimated Fair Value, Due after 1 year but within 5 years	0
Estimated Fair Value, Due after 5 years but within 10 years	0
Estimated Fair Value, Due after 10 years	9
Total	9	10	11
Available For Sale Securities Debt Maturities Amortized Cost [Abstract]
Available-for-sale debt securities, Cost	9	10	11
US government treasury obligations [Member]
Estimated Fair Value
Estimated Fair Value, Due within 1 year	6,019
Estimated Fair Value, Due after 1 year but within 5 years	1,270
Estimated Fair Value, Due after 5 years but within 10 years	140
Estimated Fair Value, Due after 10 years	0
Total	7,429	3,440	1,045
Available For Sale Securities Debt Maturities Amortized Cost [Abstract]
Available-for-sale debt securities, Cost	7,395	3,452	1,051
Corporate debt securities [Member]
Estimated Fair Value
Estimated Fair Value, Due within 1 year	5
Estimated Fair Value, Due after 1 year but within 5 years	22
Estimated Fair Value, Due after 5 years but within 10 years	0
Estimated Fair Value, Due after 10 years	0
Total	27	28	28
Available For Sale Securities Debt Maturities Amortized Cost [Abstract]
Available-for-sale debt securities, Cost	27	28	28
Mortgage-backed securities [Member]
Estimated Fair Value
Estimated Fair Value, Due within 1 year	0
Estimated Fair Value, Due after 1 year but within 5 years	0
Estimated Fair Value, Due after 5 years but within 10 years	0
Estimated Fair Value, Due after 10 years	41
Total	41	51	69
Available For Sale Securities Debt Maturities Amortized Cost [Abstract]
Available-for-sale debt securities, Cost	39	50	67
Foreign Government Bonds and Obligations [Member]
Estimated Fair Value
Estimated Fair Value, Due within 1 year	577
Estimated Fair Value, Due after 1 year but within 5 years	1
Estimated Fair Value, Due after 5 years but within 10 years	1
Estimated Fair Value, Due after 10 years	0
Total	579	474	581
Available For Sale Securities Debt Maturities Amortized Cost [Abstract]
Available-for-sale debt securities, Cost	$ 578	$ 474	$ 581

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