Investment Securities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule of Available for Sale Securities by Type
Cost	$ 3,668	$ 4,280
Gross Unrealized Gains	100	154
Gross Unrealized Losses	(9)	(3)
Estimated Fair Value	3,759	4,431	$ 0
State and municipal obligations [Member]
Schedule of Available for Sale Securities by Type
Cost	2,813	3,366
Gross Unrealized Gains	85	129
Gross Unrealized Losses	(5)	(2)
Estimated Fair Value	2,893	3,493	0
U.S. Government agency obligations [Member]
Schedule of Available for Sale Securities by Type
Cost	2	3
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	2	3	0
U.S. Government treasury obligations [Member]
Schedule of Available for Sale Securities by Type
Cost	406	346
Gross Unrealized Gains	4	4
Gross Unrealized Losses	(1)	0
Estimated Fair Value	409	350	0
Corporate debt securities [Member]
Schedule of Available for Sale Securities by Type
Cost	29	37
Gross Unrealized Gains	1	3
Gross Unrealized Losses	0	0
Estimated Fair Value	30	40	0
Mortgage-backed securities [Member]
Schedule of Available for Sale Securities by Type
Cost	117	128
Gross Unrealized Gains	4	8
Gross Unrealized Losses	0	0
Estimated Fair Value	121	136	0
Equity securities [Member]
Schedule of Available for Sale Securities by Type
Cost	1	0
Gross Unrealized Gains	0	1
Gross Unrealized Losses	0	0
Estimated Fair Value	1	1	0
Foreign government bonds and obligations [Member]
Schedule of Available for Sale Securities by Type
Cost	250	350
Gross Unrealized Gains	6	9
Gross Unrealized Losses	(1)	0
Estimated Fair Value	255	359	0
Other [Member]
Schedule of Available for Sale Securities by Type
Cost	50	50
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(2)	(1)
Estimated Fair Value	$ 48	$ 49	$ 0