Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

COLUMBIA FUNDS SERIES TRUST I

Prospectus Date

rr_ProspectusDate

Sep. 01, 2014

Supplement [Text Block]

cfsti1_SupplementTextBlock

Supplement dated January 20, 2015

To the Prospectus of the following fund:

Fund	Prospectus Dated
Columbia U.S. Treasury Index Fund	9/1/2014

Effective February 19, 2015 (the Effective Date), the Fund does not impose a sales charge (load) on the purchase of its Class A shares.

Accordingly, on the Effective Date, the Fund’s prospectus is hereby revised as follows:

The Class A column of the “Shareholder Fees” table in the “Summary of the Fund — Fees and Expenses of the Fund” section is hereby revised as follows:

Shareholder Fees (fees paid directly from your investment)
	Class A
Maximum sales charge (load) imposed on purchases (as a % of offering price)		None
Maximum deferred sales charge (load) imposed on redemptions (as a % of the lower of the original purchase price or current net asset value)		None

Additionally, the expense Example table for Class A shares (whether or not shares are redeemed) is hereby revised as follows:

	1 year		3 years		5 years		10 years
Class A (whether or not shares are redeemed)		$46		$190		$347		$803

The rest of the section remains the same.

Also, on the Effective Date, the prospectus is further revised, as applicable, to reflect that the Fund does not impose a sales charge (load) or a contingent deferred sales charge (CDSC) on the purchase of its Class A shares.

Columbia U.S. Treasury Index Fund

Risk/Return:

rr_RiskReturnAbstract

Supplement [Text Block]

cfsti1_SupplementTextBlock

Supplement dated January 20, 2015

To the Prospectus of the following fund:

Fund	Prospectus Dated
Columbia U.S. Treasury Index Fund	9/1/2014

Effective February 19, 2015 (the Effective Date), the Fund does not impose a sales charge (load) on the purchase of its Class A shares.

Accordingly, on the Effective Date, the Fund’s prospectus is hereby revised as follows:

The Class A column of the “Shareholder Fees” table in the “Summary of the Fund — Fees and Expenses of the Fund” section is hereby revised as follows:

Shareholder Fees (fees paid directly from your investment)
	Class A
Maximum sales charge (load) imposed on purchases (as a % of offering price)		None
Maximum deferred sales charge (load) imposed on redemptions (as a % of the lower of the original purchase price or current net asset value)		None

Additionally, the expense Example table for Class A shares (whether or not shares are redeemed) is hereby revised as follows:

	1 year		3 years		5 years		10 years
Class A (whether or not shares are redeemed)		$46		$190		$347		$803

The rest of the section remains the same.

Also, on the Effective Date, the prospectus is further revised, as applicable, to reflect that the Fund does not impose a sales charge (load) or a contingent deferred sales charge (CDSC) on the purchase of its Class A shares.

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder Fees (fees paid directly from your investment)

Columbia U.S. Treasury Index Fund | Class A

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a % of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) imposed on redemptions (as a % of the lower of the original purchase price or current net asset value)

rr_MaximumDeferredSalesChargeOverOther

none

1 year

rr_ExpenseExampleYear01

46

3 years

rr_ExpenseExampleYear03

190

5 years

rr_ExpenseExampleYear05

347

10 years

rr_ExpenseExampleYear10

803

1 year

rr_ExpenseExampleNoRedemptionYear01

46

3 years

rr_ExpenseExampleNoRedemptionYear03

190

5 years

rr_ExpenseExampleNoRedemptionYear05

347

10 years

rr_ExpenseExampleNoRedemptionYear10

803