Consolidated Statements Of Stockholders' Equity - USD ($) $ in Millions	Common Stock	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total
Balance as of beginning-of-year at Dec. 31, 2013	$ 6,876	$ 5,013	$ 1,563
Stock compensation/issued for benefit plans	69
Net income (loss)		1,515		$ 1,515
Retirement of common stock/cancellation of shares	(323)	(327)
Common stock dividends declared		(179)
Other comprehensive income (loss), net of tax			1,533	1,533
Balance as of end-of-period at Dec. 31, 2014	6,622	6,022	3,096	15,740
Stock compensation/issued for benefit plans	88
Net income (loss)		1,154		1,154
Retirement of common stock/cancellation of shares	(412)	(488)
Common stock dividends declared		(214)
Other comprehensive income (loss), net of tax			(2,251)	(2,251)
Balance as of end-of-period at Dec. 31, 2015	6,298	6,474	845	13,617
Stock compensation/issued for benefit plans	70
Net income (loss)		1,192		1,192
Retirement of common stock/cancellation of shares	(499)	(380)
Common stock dividends declared		(243)
Other comprehensive income (loss), net of tax			721	721
Balance as of end-of-period at Dec. 31, 2016	$ 5,869	$ 7,043	$ 1,566	$ 14,478