Investment Securities (Tables)

3 Months Ended

Mar. 31, 2019

Investment Securities (Tables) [Abstract]

Schedule of Available for Sale Securities by Type

The following is a summary of investment securities as of March 31, 2019 and December 31, 2018:

		2019								2018
					Gross		Gross		Estimated				Gross		Gross		Estimated
Description of Securities					Unrealized		Unrealized		Fair				Unrealized		Unrealized		Fair
(Millions)			Cost		Gains		Losses		Value		Cost		Gains		Losses		Value
Available-for-sale debt securities:
	State and municipal obligations	$	342	$	6	$	(1)	$	347	$	594	$	4	$	(2)	$	596
	U.S. Government agency obligations		10		―		―		10		10		―		―		10
	U.S. Government treasury obligations		5,404		14		(9)		5,409		3,452		5		(17)		3,440
	Corporate debt securities		29		―		―		29		28		―		―		28
	Mortgage-backed securities ^(a)		48		1		―		49		50		1		―		51
	Foreign government bonds and obligations		565		1		―		566		474		―		―		474
Equity securities ^(b)			50		―		(3)		47		51		―		(3)		48
Total		$	6,448	$	22	$	(13)	$	6,457	$	4,659	$	10	$	(22)	$	4,647

Represents mortgage-backed securities guaranteed by Fannie Mae, Freddie Mac or Ginnie Mae.
Equity securities comprise investments in common stock and mutual funds.

Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value

The following table provides information about our investment securities with gross unrealized losses and the length of time that individual securities have been in an unrealized loss position as of March 31, 2019 and December 31, 2018:

	2019								2018
	Less than 12 months				12 months or more				Less than 12 months				12 months or more
				Gross				Gross				Gross				Gross
Description of Securities (Millions)		Estimated Fair Value		Unrealized Losses		Estimated Fair Value		Unrealized Losses		Estimated Fair Value		Unrealized Losses		Estimated Fair Value		Unrealized Losses
State and municipal obligations	$	―	$	―	$	52	$	(1)	$	―	$	―	$	82	$	(1)
U.S. Government treasury obligations		―		―		998		(9)		224		(2)		791		(15)
Total	$	―	$	―	$	1,050	$	(10)	$	224	$	(2)	$	873	$	(16)

Available for Sale Securities Ratio of Fair Value to Amortized Cost

The following table summarizes the gross unrealized losses due to temporary impairments by ratio of fair value to amortized cost as of March 31, 2019 and December 31, 2018:

	Less than 12 months					12 months or more					Total
Ratio of Fair Value to					Gross					Gross					Gross
Amortized Cost	Number of		Estimated		Unrealized	Number of		Estimated		Unrealized	Number of		Estimated		Unrealized
(Dollars in millions)	Securities		Fair Value		Losses	Securities		Fair Value		Losses	Securities		Fair Value		Losses
2019:
90%–100%	―	$	―	$	―	26	$	1,050	$	(10)	26	$	1,050	$	(10)
Total as of March 31, 2019	―	$	―	$	―	26	$	1,050	$	(10)	26	$	1,050	$	(10)

2018:
90%–100%	2	$	224	$	(2)	29	$	873	$	(16)	31	$	1,097	$	(18)
Total as of December 31, 2018	2	$	224	$	(2)	29	$	873	$	(16)	31	$	1,097	$	(18)

Contractual maturities of investment securities

Contractual maturities for investment securities with stated maturities as of March 31, 2019 were as follows:

				Estimated
(Millions)		Cost		Fair Value
Due within 1 year	$	4,599	$	4,600
Due after 1 year but within 5 years		1,315		1,319
Due after 5 years but within 10 years		179		181
Due after 10 years		305		310
Total	$	6,398	$	6,410