Investments in Debt and Equity Securities (Details 3) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Due in one year or less, Cost Basis	$ 74		$ 74
Due after one year through five years, Cost Basis	703		703
Due after five through ten years, Cost Basis	137		137
Due after ten years, Cost Basis	18		18
Due in one year or less, Fair Value	73		73
Due after one year through five years, Fair Value	716		716
Due after five years through ten years, Fair Value	142		142
Due after ten years, Fair Value	19		19
Debt Securities, Available-for-sale, Amortized Cost	1,304		1,304		$ 1,171
Available-for-sale securities, debt securities	1,328		1,328		1,151
Schedule of Investments in Debt and Equity Securities
Unrealized gain (loss) on equity securities	2	$ 18	54	$ 20
Available-for-sale Securities, Proceeds, Gains and Losses
Proceeds from the sale of available-for-sale securities	92	41	237	181
Gross gains from the sale of available-for-sale securities	0	0	1	0
Gross losses from the sale of available-for-sale securities	0	$ 0	1	$ 0
U.S. governmental agency mortgage-backed securities
Investments, Debt and Equity Securities [Abstract]
Debt Securities, Available-for-sale, Amortized Cost	326		326		301
Available-for-sale securities, debt securities	331		331		297
Residential
Investments, Debt and Equity Securities [Abstract]
Debt Securities, Available-for-sale, Amortized Cost	6		6		7
Available-for-sale securities, debt securities	6		6		7
Commercial
Investments, Debt and Equity Securities [Abstract]
Debt Securities, Available-for-sale, Amortized Cost	40		40		14
Available-for-sale securities, debt securities	$ 41		$ 41		$ 13