AVAILABLE FOR SALE SECURITIES (Tables)

12 Months Ended

Sep. 30, 2020

Investments, Debt and Equity Securities [Abstract]

Amortized Cost and Estimated Fair Values of Available For Sale Securities

The following table details the amortized costs and fair values of our available-for-sale securities.

$ in millions	Cost basis		Gross unrealized gains		Gross unrealized losses		Fair value
September 30, 2020
Agency residential MBS	$	4,064	$	74	$	(3)	$	4,135
Agency commercial MBS	948		22		(1)		969
Agency CMOs	2,504		27		(1)		2,530
Other securities	15		1		—		16
Total available-for-sale securities	$	7,531	$	124	$	(5)	$	7,650
September 30, 2019
Agency residential MBS	$	1,555	$	20	$	(1)	$	1,574
Agency commercial MBS	305		5		—		310
Agency CMOs	1,195		7		(3)		1,199
Other securities	10		—		—		10
Total available-for-sale securities	$	3,065	$	32	$	(4)	$	3,093

Contractual Maturities, Amortized Cost, Carrying Values, and Current Yields for Available For Sales Securities

The following table details the contractual maturities, amortized costs, carrying values and current yields for our available-for-sale securities.  Since our MBS and CMO available-for-sale securities are backed by mortgages, actual maturities may differ from contractual maturities because borrowers may have the right to prepay obligations without prepayment penalties. As of September 30, 2020, the duration of our available-for-sale securities portfolio was approximately three years.

	September 30, 2020
$ in millions	Within one year			After one but within five years			After five but within ten years			After ten years			Total
Agency residential MBS
Amortized cost	$	—		$	34		$	1,403		$	2,627		$	4,064
Carrying value	$	—		$	36		$	1,434		$	2,665		$	4,135
Agency commercial MBS
Amortized cost	$	32		$	153		$	583		$	180		$	948
Carrying value	$	33		$	157		$	598		$	181		$	969
Agency CMOs
Amortized cost	$	—		$	11		$	74		$	2,419		$	2,504
Carrying value	$	—		$	11		$	75		$	2,444		$	2,530
Other securities
Amortized cost	$	—		$	6		$	9		$	—		$	15
Carrying value	$	—		$	6		$	10		$	—		$	16
Total available-for-sale securities
Amortized cost	$	32		$	204		$	2,069		$	5,226		$	7,531
Carrying value	$	33		$	210		$	2,117		$	5,290		$	7,650
Weighted-average yield	2.72		%	2.06		%	1.67		%	1.41		%	1.51		%

Available For Sale Securities in a Continuous Unrealized Loss Position

The following table details the gross unrealized losses and fair values of securities that were in a loss position at the reporting period end, aggregated by investment category and length of time the individual securities have been in a continuous unrealized loss position.

	Less than 12 months				12 months or more				Total
$ in millions	Estimated fair value		Unrealized losses		Estimated fair value		Unrealized losses		Estimated fair value		Unrealized losses
September 30, 2020
Agency residential MBS	$	966	$	(3)	$	—	$	—	$	966	$	(3)
Agency commercial MBS	177		(1)		—		—		177		(1)
Agency CMOs	410		(1)		—		—		410		(1)
Total	$	1,553	$	(5)	$	—	$	—	$	1,553	$	(5)
September 30, 2019
Agency residential MBS	$	166	$	—	$	114	$	(1)	$	280	$	(1)
Agency commercial MBS	—		—		44		—		44		—
Agency CMOs	145		(1)		351		(2)		496		(3)
Other securities	2		—		—		—		2		—
Total	$	313	$	(1)	$	509	$	(3)	$	822	$	(4)