Noncontrolling Interests on the Company's Consolidated Financial Statements (Details) $ / shares in Units, $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2025 USD ($) trading_day $ / shares shares	Dec. 31, 2024 USD ($) $ / shares shares
Noncontrolling Interest [Line Items]
Common stock, par value (in dollars per share) \| $ / shares	$ 0.01	$ 0.01
Number of trading days \| trading_day	10
Aggregate value upon redemption of outstanding noncontrolling common units \| $	$ 50.1	$ 46.8
Non-Affiliated Investors and Former Executive Officer and Director \| Common Units
Noncontrolling Interest [Line Items]
Common units outstanding held by common limited partners (in shares)	1,150,574	1,150,574
Kilroy Realty L.P. \| Common Units
Noncontrolling Interest [Line Items]
Conversion ratio	1
Kilroy Realty L.P. \| Common Units
Noncontrolling Interest [Line Items]
Common units outstanding held by common limited partners (in shares)	1,150,574	1,150,574
Operating Partnership
Noncontrolling Interest [Line Items]
Ownership interest (percent)	99.00%	99.00%
Operating Partnership \| Non-Affiliated Investors and Former Executive Officer and Director
Noncontrolling Interest [Line Items]
Ownership interest (percent)	1.00%	1.00%

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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+ References

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 272
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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 505
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The fair value as of the reporting date of noncontrolling interests which are redeemable by the (parent) entity (1) at a fixed or determinable price on a fixed or determinable date, (2) at the option of the holder of the noncontrolling interest, or (3) upon occurrence of an event that is not solely within the control of the (parent) entity. The noncontrolling interest holder's ownership (or holders' ownership) may be in the form of common shares (regardless of class), limited partnership units (regardless of class), non-preferential membership interests, or any other form of common equity regardless of investee entity legal form.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 480
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