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, 2012	$ 7,121	$ 4,044	$ 3,808
Stock compensation/issued for benefit plans	69
Net income (loss)		1,244		$ 1,244
Retirement of common stock/cancellation of shares	(314)	(136)
Common stock dividends declared (2015 - $0.60; 2014 - $0.48)		(139)
Other comprehensive income (loss), net of tax			(2,245)	(2,245)
Balance as of end-of-period at Dec. 31, 2013	6,876	5,013	1,563	13,452
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 (2015 - $0.60; 2014 - $0.48)		(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 (2015 - $0.60; 2014 - $0.48)		(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