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 Mar. 31, 2015	$ 21,071	1,565
Balance at beginning of period at Dec. 31, 2014			$ 0	$ 14,170	$ 1,233	$ (1)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Capital contribution from parent				4,000
Employee benefit plans				4
Net income	164				164
Cash dividends declared on preferred stock					(18)
Other comprehensive income (loss), net of tax	(46)					(46)
Balance at end of period at Mar. 31, 2015	19,506		0	18,174	1,379	(47)
Balance at beginning of period at Dec. 31, 2015	20,525	1,265
Balance at end of period at Mar. 31, 2016	20,896	$ 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]
Capital contribution from parent				0
Employee benefit plans				(2)
Net income	154				154
Cash dividends declared on preferred stock					(14)
Other comprehensive income (loss), net of tax	233					233
Balance at end of period at Mar. 31, 2016	$ 19,631		$ 0	$ 18,167	$ 1,638	$ (174)