Secured and Unsecured Debt of the Operating Partnership - Narrative (Details) $ in Millions	Feb. 11, 2019 USD ($)
Kilroy Realty L.P. [Member] \| Secured debt [Member] \| 6.05% Mortgage Payable Due June 1, 2019 [Member]
Debt Instrument [Line Items]
Repayments of Notes Payable	$ 74.3

The cash outflow for a borrowing supported by a written promise to pay an obligation.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3291-108585

Name:	us-gaap_RepaymentsOfNotesPayable
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration