Income Taxes - Additional Information (Details) $ in Millions, € in Billions				1 Months Ended	3 Months Ended			9 Months Ended
	Jan. 01, 2018	Dec. 31, 2017	Aug. 30, 2016 EUR (€) Subsidiary	Aug. 01, 2018 EUR (€)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 30, 2017 USD ($)	Jun. 30, 2018 USD ($)	Jul. 01, 2017 USD ($)	Jun. 30, 2018 EUR (€)	Sep. 30, 2017 USD ($)
Income Tax Contingency [Line Items]
U.S. statutory federal income tax rate	21.00%	35.00%
Provision for income taxes related to the Act, provisional amount							$ 2,600	$ 900
Provision for income taxes related to remeasurement of deferred tax balances, provisional amount							1,800
Provision for income taxes related to deemed repatriation tax, provisional amount							800
Provision for income taxes related to the Act, provisional amount, measurement period reduction					$ 1,000
Increase/(Reduction) to unrecognized tax benefits related to deemed repatriation tax					(700)		(1,100)	(1,800)
Deferred tax liability for unremitted foreign earnings											$ 36,400
Deferred tax liability reversal								33,109	$ (4,764)
Deemed repatriation tax payable, provisional amount					37,000		38,000	37,000
Gross unrecognized tax benefits					9,400			9,400
Unrecognized tax benefits that would impact effective tax rate, if recognized					7,300			7,300
Unrecognized tax benefits, gross interest and penalties accrued					1,300			1,300
Reasonably possible decrease in gross unrecognized tax benefits over next 12 months					500			500
Recovery amount funded into escrow and restricted from general use related to the State Aid Decision					$ 8,800			8,800
Unfavorable investigation outcome, EU State Aid rules
Income Tax Contingency [Line Items]
Number of subsidiaries impacted by European Commission tax ruling | Subsidiary			2
Maximum potential loss related to European Commission tax ruling | €			€ 13.0
Recovery amount funded into escrow and restricted from general use related to the State Aid Decision | €										€ 4.5
Unfavorable investigation outcome, EU State Aid rules - interest component
Income Tax Contingency [Line Items]
Maximum potential loss related to European Commission tax ruling | €			€ 1.0
Subsequent event | Unfavorable investigation outcome, EU State Aid rules
Income Tax Contingency [Line Items]
Recovery amount funded into escrow and restricted from general use related to the State Aid Decision, subsequent to June 30, 2018 | €				€ 4.5
Tax Cuts and Jobs Act, deemed repatriation tax, related amount
Income Tax Contingency [Line Items]
Deferred tax liability reversal							$ 36,100
Accumulated other comprehensive income/(loss)
Income Tax Contingency [Line Items]
Reclassification from AOCI to retained earnings, tax effects of the Act								$ (278)
Accounting Standards Update 2018-02 | Accumulated other comprehensive income/(loss)
Income Tax Contingency [Line Items]
Reclassification from AOCI to retained earnings, tax effects of the Act						$ (278)
Accounting Standards Update 2018-02 | Retained earnings
Income Tax Contingency [Line Items]
Reclassification from AOCI to retained earnings, tax effects of the Act						$ 278