Shareholders' Equity - Repurchases of Common Shares in the Open Market (Details) - Open market repurchases - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended						6 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 30, 2017	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 31, 2016	Mar. 31, 2018	Sep. 30, 2017
Stock Repurchase Program [Line Items]
Number of shares repurchased (in shares)	137,040	30,181	29,073	30,356	31,070	44,333	167,221	134,832
Average repurchase price per share (in dollars per share)	$ 171.48	$ 169.26	$ 154.78	$ 148.24	$ 128.74	$ 112.78
Amount	$ 23,500	$ 5,109	$ 4,500	$ 4,500	$ 4,001	$ 5,000	$ 28,609	$ 18,001