Inventories, Net - Anticipated Annual Amortization Expense for Pre-Production Engineering Costs (Details) $ in Millions	3 Months Ended
Dec. 31, 2017 USD ($)
Inventory Disclosure [Abstract]
2018	$ 90
2019	132
2020	149
2021	147
2022	139
Thereafter	$ 550

- Definition

The amount of amortization expense related to deferred pre-production engineering costs expected to be recognized after the fifth twelve-month period following the balance sheet date.

+ References

No definition available.

+ Details

Name:	col_DeferredPreProductionEngineeringCostsFutureAmortizationExpenseAfterYearFive
Namespace Prefix:	col_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Deferred Pre Production Engineering Costs Future Amortization Expense, Remainder Of Fiscal Year

+ References

No definition available.

+ Details

Name:	col_DeferredPreProductionEngineeringCostsFutureAmortizationExpenseRemainderOfFiscalYear
Namespace Prefix:	col_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount of amortization expense related to deferred pre-production engineering costs expected to be recognized during the fifth twelve-month period following the balance sheet date.

+ References

No definition available.

+ Details

Name:	col_DeferredPreProductionEngineeringCostsFutureAmortizationExpenseYearFive
Namespace Prefix:	col_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount of amortization expense related to deferred pre-production engineering costs expected to be recognized during the fourth twelve-month period following the balance sheet date.

+ References

No definition available.

+ Details

Name:	col_DeferredPreProductionEngineeringCostsFutureAmortizationExpenseYearFour
Namespace Prefix:	col_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount of amortization expense related to deferred pre-production engineering costs expected to be recognized during the third twelve-month period following the balance sheet date.

+ References

No definition available.

+ Details

Name:	col_DeferredPreProductionEngineeringCostsFutureAmortizationExpenseYearThree
Namespace Prefix:	col_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount of amortization expense related to deferred pre-production engineering costs expected to be recognized during the second twelve-month period following the balance sheet date.

+ References

No definition available.

+ Details

Name:	col_DeferredPreProductionEngineeringCostsFutureAmortizationExpenseYearTwo
Namespace Prefix:	col_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- References

No definition available.

+ Details

Name:	us-gaap_InventoryDisclosureAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration