Investment Securities (Details 3) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($)
Estimated Fair Value
Estimated Fair Value, Due within 1 year	$ 340
Estimated Fair Value, Due after 1 year but within 5 years	252
Estimated Fair Value, Due after 5 years but within 10 years	409
Estimated Fair Value, Due after 10 years	2,709
Total	3,710
Available For Sale Securities Debt Maturities Amortized Cost [Abstract]
Due within 1 year	340
Due after 1 year but within 5 years	247
Due after 5 years but within 10 years	395
Due after 10 years	2,635
Total	$ 3,617
Weighted average yields
Weighted average yields, due within 1 year	2.86%
Weighted averge yields, due after 1 years but within 5 years	2.78%
Weighted averge yields, due after 5 years but within 10 years	5.48%
Weighted average yield, due after 10 years	6.58%
Weighted average yields, Total	5.85%
State and municipal obligations [Member]
Estimated Fair Value
Estimated Fair Value, Due within 1 year	$ 23
Estimated Fair Value, Due after 1 year but within 5 years	61
Estimated Fair Value, Due after 5 years but within 10 years	277
Estimated Fair Value, Due after 10 years	2,532
Total	2,893
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	2
Total	2
U.S. Government agency obligations [Member]
Estimated Fair Value
Estimated Fair Value, Due within 1 year	120
Estimated Fair Value, Due after 1 year but within 5 years	144
Estimated Fair Value, Due after 5 years but within 10 years	132
Estimated Fair Value, Due after 10 years	13
Total	409
Corporate debt securities [Member]
Estimated Fair Value
Estimated Fair Value, Due within 1 year	6
Estimated Fair Value, Due after 1 year but within 5 years	24
Estimated Fair Value, Due after 5 years but within 10 years	0
Estimated Fair Value, Due after 10 years	0
Total	30
Mortgage-backed securities [Member]
Estimated Fair Value
Estimated Fair Value, Due within 1 year	1
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	120
Total	121
Foreign government bonds and obligations [Member]
Estimated Fair Value
Estimated Fair Value, Due within 1 year	190
Estimated Fair Value, Due after 1 year but within 5 years	23
Estimated Fair Value, Due after 5 years but within 10 years	0
Estimated Fair Value, Due after 10 years	42
Total	$ 255