Shareholder's Equity - Common Share Rollforward (Details) - shares				12 Months Ended
	Dec. 26, 2017	Mar. 09, 2017	Nov. 03, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Common stock, shares issued, beginning balance (in shares)				268,079,931
Common stock, shares outstanding, beginning balance (in shares)				194,639,273	209,100,000	241,900,000
Common stock, shares issued (in shares)				0	0	0
Common stock, shares acquired under share repurchase (in shares)	7,821,666	3,986,647	5,216,025	24,400,000	(17,000,000)	34,300,000
Common stock, shares issued for share-based compensation programs (in shares)				1,800,000	2,500,000	1,500,000
Common stock, shares issued, ending balance (in shares)				270,078,294	268,079,931
Common stock, shares outstanding, ending balance (in shares)				171,982,673	194,639,273	209,100,000
Common stock
Common stock, shares issued, beginning balance (in shares)				268,000,000	265,300,000	263,700,000
Common stock, shares issued (in shares)				0	0	0
Common stock, shares acquired under share repurchase (in shares)				0	0	0
Common stock, shares issued for share-based compensation programs (in shares)				2,000,000	2,700,000	1,600,000
Common stock, shares issued, ending balance (in shares)				270,000,000	268,000,000	265,300,000
Treasury stock
Common stock, shares held in treasury, beginning balance (in shares)				(73,400,000)	(56,200,000)	(21,800,000)
Common stock, shares issued (in shares)				0	0	0
Common stock, shares acquired under share repurchase (in shares)				24,400,000	(17,000,000)	34,300,000
Common stock, shares issued for share-based compensation programs (in shares)				200,000	(200,000)	100,000
Common stock, shares held in treasury, ending balance (in shares)				(98,000,000)	(73,400,000)	(56,200,000)