CONSOLIDATED STATEMENT OF CHANGES IN SHAREHOLDERS' EQUITY - USD ($) $ in Millions	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]
Balance at beginning of period at Dec. 31, 2014		$ 1,565
Balance at end of period at Sep. 30, 2015	$ 20,820	1,265
Balance at beginning of period at Dec. 31, 2014			$ 0	$ 14,170	$ 1,233	$ (1)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Preferred stock issuance		0
Preferred stock redemption		(300)
Capital contribution from parent				4,000
Employee benefit plans				3
Net income	455				455
Cash dividends declared on preferred stock					(50)
Other comprehensive income (loss), net of tax	(255)					(255)
Balance at end of period at Sep. 30, 2015	19,555		0	18,173	1,638	(256)
Balance at beginning of period at Dec. 31, 2015	20,525	1,265
Balance at end of period at Sep. 30, 2016	20,977	1,265
Balance at beginning of period at Dec. 31, 2015	19,260		0	18,169	1,498	(407)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Preferred stock issuance		1,265
Preferred stock redemption		$ (1,265)
Capital contribution from parent				0
Employee benefit plans				(12)
Net income	166				166
Cash dividends declared on preferred stock					(29)
Other comprehensive income (loss), net of tax	327					327
Balance at end of period at Sep. 30, 2016	$ 19,712		$ 0	$ 18,157	$ 1,635	$ (80)