Stockholders' Equity (Details) - USD ($) $ / shares in Units, $ in Billions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Stockholders' Equity Note [Abstract]
Common stock authorized for repurchase	$ 3.8
Shares of preferred stock authorized to issue (in shares)	10,000,000	10,000,000
Par value of authorized preferred stock (in dollars per share)	$ 0.01	$ 0.01
Capital in excess of par value plus the retained earnings	$ 9.0
Class of Stock [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance	15,126,347
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance (in shares)	194,972,445	221,428,308	246,696,136
Purchase of treasury stock (in shares)	(5,130,334)	(27,970,492)	(26,955,623)
Stock issued under stock compensation plans (in shares)	1,337,803	1,514,629	1,687,795
Balance (in shares)	(191,179,914)	194,972,445	221,428,308
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance (in shares)	263,111,472	263,111,472	263,111,472
Purchase of treasury stock (in shares)	0	0	0
Stock issued under stock compensation plans (in shares)	0	0	0
Balance (in shares)	263,111,472	263,111,472	263,111,472
Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance (in shares)	(68,139,027)	(41,683,164)	(16,415,336)
Purchase of treasury stock (in shares)	(5,130,334)	(27,970,492)	(26,955,623)
Stock issued under stock compensation plans (in shares)	1,337,803	1,514,629	1,687,795
Balance (in shares)	(71,931,558)	(68,139,027)	(41,683,164)