CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 1,791	$ 1,721	$ 1,652
Other comprehensive income (loss):
Net unrealized derivative instruments gains (losses) arising during the periods, net of income taxes of $35, ($11) and ($9), respectively	103
Net unrealized derivative instruments gains (losses) arising during the periods, net of income taxes of $35, ($11) and ($9), respectively, before 2017-12 adoption		(33)	(14)
Reclassification adjustment for net derivative losses (gains) included in net income, net of income taxes of $14, $10 and ($9), respectively	43
Reclassification adjustment for net derivative losses (gains) included in net income, net of income taxes of $14, $10 and ($9), respectively, before 2017-12 adoption		33	(16)
Net unrealized debt securities gains (losses) arising during the periods, net of income taxes of $165, ($79) and ($4), respectively	501	(239)	(6)
Other-than-temporary impairment not recognized in earnings on debt securities, net of income taxes of $0, ($1) and $0, respectively	0	(3)	0
Reclassification of net debt securities gains to net income, net of income taxes of ($8), ($4) and ($2), respectively	(15)	(12)	(2)
Employee benefit plans:
Actuarial gain (loss), net of income taxes of $12, ($14) and $12, respectively	36	(35)	19
Amortization of actuarial loss, net of income taxes of $6, $3 and $5, respectively	13	14	13
Amortization of prior service cost, net of income taxes of $0, $0 and $0, respectively	(1)	(1)	(1)
Total other comprehensive income (loss), net of income taxes	680	(276)	(7)
Total comprehensive income	$ 2,471	$ 1,445	$ 1,645