Consolidated Statement of Stockholder's Equity - USD ($) $ in Millions	Total	Common Stock	Capital in excess of par value	Retained earnings	Accumulated other comprehensive income (loss)	Treasury stock
Balance at beginning of period at Dec. 31, 2012	$ 6,992	$ 808	$ 1,210	$ 5,768	$ (119)	$ (675)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Repurchase of common stock	(540)	0	0	0	0	(540)
Issuance of common and treasury stock pursuant to Employee stock plans	96	0	12	0	0	84
Net tax benefit (expense) of options exercised		0		0	0	0
Adjustments to Additional Paid in Capital, Income Tax Deficiency from Share-based Compensation	(9)		(9)
Share-based compensation	18	0	18	0	0	0
Cash dividends	(91)	0	0	(91)	0	0
Comprehensive income	870	0	0	754	116	0
Balance at end of period at Dec. 31, 2013	7,336	808	1,231	6,431	(3)	(1,131)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Repurchase of common stock	(955)	0	0	0	0	(955)
Issuance of common and treasury stock pursuant to Employee stock plans	100	0	40	0	0	60
Net tax benefit (expense) of options exercised	23	0	23	0	0	0
Share-based compensation	21	0	21	0	0	0
Cash dividends	(151)	0	0	(151)	0	0
Comprehensive income	401	0	0	1,136	(735)	0
Balance at end of period at Dec. 31, 2014	6,775	808	1,315	7,416	(738)	(2,026)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Repurchase of common stock	(1,180)	0	0	0	0	(1,180)
Issuance of common and treasury stock pursuant to Employee stock plans	30	0	6	0	0	24
Net tax benefit (expense) of options exercised	24	0	24	0	0	0
Share-based compensation	29	0	29	0	0	0
Cash dividends	(188)	0	0	(188)	0	0
Comprehensive income	1,868	0	0	2,181	(313)	0
Balance at end of period at Dec. 31, 2015	$ 7,358	$ 808	$ 1,374	$ 9,409	$ (1,051)	$ (3,182)