CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 449	$ 443	$ 1,341	$ 1,256
Other comprehensive income (loss):
Net unrealized derivative instruments (losses) gains arising during the periods, net of income taxes of ($1), ($9), $35 and ($31), respectively	(4)		103
Net unrealized derivative instrument gains (losses) arising during the periods, net of income taxes of ($1), ($9), $35 and ($31), respectively, before 2017-12 adoption		(26)		(91)
Reclassification adjustment for net derivative losses included in net income, net of income taxes of $4, $3, $13 and $6, respectively	10		40
Reclassification adjustment for net derivative losses, included in net income, net of income taxes of $4, $3, $13, and $6, respectively, before 2017-12 adoption		11		19
Net unrealized debt securities gains (losses) arising during the periods, net of income taxes of $13, ($34), $165 and ($139), respectively	42	(95)	509	(427)
Other-than-temporary impairment not recognized in earnings on debt securities, net of income taxes of $0, ($1), $0 and ($1), respectively	(1)	0	0	(1)
Reclassification of net debt securities gains to net income, net of income taxes of $0, $0, ($3) and ($2), respectively	(2)	(2)	(10)	(8)
Amortization of actuarial loss, net of income taxes of $2, $1, $5 and $3, respectively	3	4	9	10
Net other comprehensive (loss) income	48	(108)	651	(498)
Total comprehensive income	$ 497	$ 335	$ 1,992	$ 758