Partners' Capital of the Operating Partnership (Details) - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
General Partners' Capital Account [Abstract]
Net proceeds from issuance of common stock	$ 387,509	$ 22,136
Noncontrolling Interest, Ownership Percentage by Parent	98.10%	97.90%	98.00%
Common units held by limited partners	1,788,170	1,804,200	1,804,200
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	1.90%	2.10%	2.00%
Kilroy Realty, L.P. [Member] \| Capital Units [Member]
General Partners' Capital Account [Abstract]
General Partners' Capital Account, Units Outstanding	92,220,367	83,388,220	86,259,684

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The number of general partner units outstanding.

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The number of limited partner units outstanding.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 5

-Subparagraph (SAB TOPIC 4.F)

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-Name Accounting Standards Codification

-Topic 272

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-Section 50

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-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 4

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The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

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The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

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The cash inflow from the additional capital contribution to the entity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

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-Section 45

-Paragraph 14

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