CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Millions	Total	Common Stock	Capital in Excess of Par Value	Treasury Stock, at Cost	Accumulated Other Comprehensive Loss	Retained Earnings
Stockholders' Equity at Dec. 31, 2014	$ 2,127	$ 1	$ 296	$ (4)	$ (310)	$ 2,144
Common Stock Outstanding at Dec. 31, 2014		131,481,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	848					848
Other comprehensive income (loss)	$ 7				7
Common stock repurchase (in shares)	(7,208,328)	(7,208,000)
Common stock repurchase	$ (505)		(259)	(246)
Stock-based compensation	17		17
Cash dividend declared	(102)					(102)
Stock issued for employee stock purchase plan (in shares)		281,000
Stock issued for employee stock purchase plan	13		13
Stock issued under stock plans (in shares)		621,000
Stock issued under stock plans	6		6
Stockholders' Equity at Dec. 31, 2015	2,411	$ 1	73	(250)	(303)	2,890
Common Stock Outstanding at Dec. 31, 2015		125,175,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	814					814
Other comprehensive income (loss)	$ (2)				(2)
Common stock repurchase (in shares)	(2,594,809)	(2,595,000)
Common stock repurchase	$ (193)		0	(193)
Stock-based compensation	19		19
Cash dividend declared	(136)					(136)
Stock issued for employee stock purchase plan (in shares)		309,000
Stock issued for employee stock purchase plan	17		17
Stock issued under stock plans (in shares)		439,000
Stock issued under stock plans	1		1
Stockholders' Equity at Dec. 31, 2016	$ 2,931	$ 1	110	(443)	(305)	3,568
Common Stock Outstanding at Dec. 31, 2016	123,328,051	123,328,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	$ 1,034					1,034
Other comprehensive income (loss)	$ (75)				(75)
Common stock repurchase (in shares)	(981,277)	(981,000)
Common stock repurchase	$ (75)		0	(75)
Stock-based compensation	34		34
Cash dividend declared	(148)					(148)
Stock issued for employee stock purchase plan (in shares)		407,000
Stock issued for employee stock purchase plan	24		24
Stock issued under stock plans (in shares)		307,000
Stock issued under stock plans	(4)		(4)
Stockholders' Equity at Dec. 31, 2017	$ 3,721	$ 1	$ 164	$ (518)	$ (380)	$ 4,454
Common Stock Outstanding at Dec. 31, 2017	123,060,638	123,061,000