Investment Securities (Details 3) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Estimated Fair Value
Estimated Fair Value, Due within 1 year	$ 2,262
Estimated Fair Value, Due after 1 year but within 5 years	1,607
Estimated Fair Value, Due after 5 years but within 10 years	197
Estimated Fair Value, Due after 10 years	533
Total		$ 3,111
Available For Sale Securities Debt Maturities Amortized Cost [Abstract]
Due within 1 year	2,261
Due after 1 year but within 5 years	1,617
Due after 5 years but within 10 years	199
Due after 10 years	531
Total	$ 4,608
Weighted average yields
Weighted average yields, due within 1 year	2.81%
Weighted averge yields, due after 1 years but within 5 years	2.15%
Weighted averge yields, due after 5 years but within 10 years	3.49%
Weighted average yield, due after 10 years	3.53%
Weighted average yields, Total	2.69%
State and municipal obligations [Member]
Estimated Fair Value
Estimated Fair Value, Due within 1 year	$ 13
Estimated Fair Value, Due after 1 year but within 5 years	47
Estimated Fair Value, Due after 5 years but within 10 years	66
Estimated Fair Value, Due after 10 years	470
Total	596
U.S. Government treasury 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	10
Total	10
U.S. Government agency obligations [Member]
Estimated Fair Value
Estimated Fair Value, Due within 1 year	1,773
Estimated Fair Value, Due after 1 year but within 5 years	1,534
Estimated Fair Value, Due after 5 years but within 10 years	131
Estimated Fair Value, Due after 10 years	2
Total	3,440
Corporate debt securities [Member]
Estimated Fair Value
Estimated Fair Value, Due within 1 year	2
Estimated Fair Value, Due after 1 year but within 5 years	26
Estimated Fair Value, Due after 5 years but within 10 years	0
Estimated Fair Value, Due after 10 years	0
Total	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	51
Total	51
Foreign government bonds and obligations [Member]
Estimated Fair Value
Estimated Fair Value, Due within 1 year	474
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	0
Total	$ 474