Equity (Details) SFr / shares in Units, $ / shares in Units, SFr in Millions, $ in Millions	1 Months Ended								3 Months Ended																12 Months Ended
	Mar. 31, 2016 installment SFr / shares	Mar. 31, 2016 installment $ / shares	Mar. 31, 2015 installment SFr / shares	Mar. 31, 2015 installment $ / shares	Mar. 31, 2014 installment SFr / shares	Mar. 31, 2014 installment $ / shares	Mar. 31, 2013 installment SFr / shares	Mar. 31, 2013 installment $ / shares	Mar. 31, 2017 $ / shares	Dec. 30, 2016 $ / shares	Sep. 30, 2016 CHF (SFr) $ / shares shares	Jun. 24, 2016 $ / shares	Mar. 25, 2016 $ / shares	Dec. 25, 2015 $ / shares	Sep. 25, 2015 CHF (SFr) $ / shares shares	Jun. 26, 2015 $ / shares	Mar. 27, 2015 $ / shares	Dec. 26, 2014 $ / shares	Sep. 26, 2014 $ / shares	Jun. 27, 2014 $ / shares	Mar. 28, 2014 $ / shares	Dec. 27, 2013 $ / shares	Sep. 27, 2013 $ / shares	Jun. 28, 2013 $ / shares	Sep. 30, 2016 USD ($) $ / shares shares	Sep. 25, 2015 USD ($) $ / shares shares	Sep. 26, 2014 USD ($) $ / shares shares	Sep. 30, 2016 USD ($) shares	Sep. 25, 2015 USD ($) shares
Equity
Maximum percentage of shares that the board may authorize for issuance																									50.00%
Treasury shares | shares											27,554,005				20,071,089													27,554,005	20,071,089
Common shares held in treasury, owned by subsidiary | shares											2,000,000				6,000,000													2,000,000	6,000,000
Cancellation of treasury shares (in shares) | shares																									31,000,000	5,000,000	10,000,000
Contributed surplus established for Swiss tax and statutory purposes ("Swiss Contributed Surplus")											SFr 7,878				SFr 8,392													$ 6,992	$ 7,505
Dividend or cash distribution approved (in currency per share) | (per share)	SFr 1.48	$ 1.48	SFr 1.27	$ 1.32	SFr 1.04	$ 1.16	SFr 0.96	$ 1.00
Number of quarterly dividend installments | installment	4	4	4	4	4	4	4	4
Cash dividend paid (in dollars per share) | $ / shares											SFr 0.37	$ 0.37	$ 0.33	$ 0.33	SFr 0.33	$ 0.33	$ 0.29	$ 0.29	$ 0.29	$ 0.29	$ 0.25	$ 0.25	$ 0.25	$ 0.25	$ 1.40	$ 1.24	$ 1.08
Cash dividend to be paid in the future (in dollars per share) | $ / shares									$ 0.37	$ 0.37
Unpaid portion of the dividend payment recorded in accrued and other current liabilities | $																												263	$ 260
Share repurchase program, increase in authorized amount | $																									$ 1,000
Number of common shares repurchased | shares																									43,000,000	18,000,000	11,000,000
Amount repurchased | $																									$ 2,610	$ 1,163	$ 604
Amount available for repurchase, at end of period | $																												$ 1,100