Advances (Advances by Year of Contractual Maturity or Next Put/Convert Date for Putable/Convertible Advances) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Advances [Abstract]
Federal Home Loan Bank, Advances, Earlier of Contractual Maturity or Next Put Date, Due within One Year of Balance Sheet Date	$ 36,545,070	$ 23,499,560
Federal Home Loan Bank, Advances, Earlier of Contractual Maturity or Next Put Date, Due From One To Two Years of Balance Sheet Date	17,097,173	21,248,138
Federal Home Loan Bank, Advances, Earlier of Contractual Maturity or Next Put Date, Due From Two To Three Years of Balance Sheet Date	10,306,830	14,286,853
Federal Home Loan Bank, Advances, Earlier of Contractual Maturity or Next Put Date, Due From Three To Four Years of Balance Sheet Date	1,887,708	5,322,050
Federal Home Loan Bank, Advances, Earlier of Contractual Maturity or Next Put Date, Due From Four To Five Years of Balance Sheet Date	727,943	963,105
Federal Home Loan Bank, Advances, Earlier of Contractual Maturity or Next Put Date, Due After Five Years of Balance Sheet Date	4,547,756	4,587,315
Federal Home Loan Bank, Advances, Par Value, Total	$ 71,112,480	$ 69,907,021

Advances [Abstract]

No definition available.

Name:	fhlbcin_AdvancesAbstract
Namespace Prefix:	fhlbcin_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Par amount of advances made and reported by Federal Home Loan Bank (FHLBank) with the earlier of contractual maturity or next put or convert date after the fifth rolling twelve months following the latest balance sheet. For interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

No definition available.

+ Details

Name:	us-gaap_FederalHomeLoanBankAdvancesEarlierOfContractualMaturityOrNextPutOrConvertDateAfterRollingYearFive
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Par amount of advances made and reported by Federal Home Loan Bank (FHLBank) with the earlier of contractual maturity or next put or convert date within the next rolling twelve months following the latest balance sheet. For interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

No definition available.

+ Details

Name:	us-gaap_FederalHomeLoanBankAdvancesEarlierOfContractualMaturityOrNextPutOrConvertDateInNextRollingTwelveMonths
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Par amount of advances made and reported by Federal Home Loan Bank (FHLBank) with the earlier of contractual maturity or next put or convert date within the fifth rolling twelve months following the latest balance sheet. For interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

No definition available.

+ Details

Name:	us-gaap_FederalHomeLoanBankAdvancesEarlierOfContractualMaturityOrNextPutOrConvertDateInRollingYearFive
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Par amount of advances made and reported by Federal Home Loan Bank (FHLBank) with the earlier of contractual maturity or next put or convert date within the fourth rolling twelve months following the latest balance sheet. For interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

No definition available.

+ Details

Name:	us-gaap_FederalHomeLoanBankAdvancesEarlierOfContractualMaturityOrNextPutOrConvertDateInRollingYearFour
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Par amount of advances made and reported by Federal Home Loan Bank (FHLBank) with the earlier of contractual maturity or next put or convert date within the third rolling twelve months following the latest balance sheet. For interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

No definition available.

+ Details

Name:	us-gaap_FederalHomeLoanBankAdvancesEarlierOfContractualMaturityOrNextPutOrConvertDateInRollingYearThree
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Par amount of advances made and reported by Federal Home Loan Bank (FHLBank) with the earlier of contractual maturity or next put or convert date within the second rolling twelve months following the latest balance sheet. For interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

No definition available.

+ Details

Name:	us-gaap_FederalHomeLoanBankAdvancesEarlierOfContractualMaturityOrNextPutOrConvertDateInRollingYearTwo
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Par amount of advances made and reported by Federal Home Loan Bank (FHLBank).

+ References

No definition available.

+ Details

Name:	us-gaap_FederalHomeLoanBankAdvancesParValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant