Noncontrolling Interests on the Company’s Consolidated Financial Statements - Narrative (Details) $ / shares in Units, $ in Thousands	12 Months Ended
Dec. 31, 2019 USD ($) d $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares
Noncontrolling Interest [Line Items]
Ownership interest of noncontrolling interest	1.90%	2.00%
Conversion ratio	1
Common stock, par value (in dollars per share) \| $ / shares	$ 0.01	$ 0.01
Trading days \| d	10
Aggregate value upon redemption of outstanding noncontrolling common units	$ 167,700	$ 126,400
Noncontrolling interest in consolidated subsidiary	195,431	192,363
100 First LLC & 303 Second LLC [Member]
Noncontrolling Interest [Line Items]
Noncontrolling interest in consolidated subsidiary		186,400
Redwood LLC [Member]
Noncontrolling Interest [Line Items]
Noncontrolling interest in consolidated subsidiary	$ 5,800	$ 6,000
Common units [Member] \| Kilroy Realty L.P. [Member]
Noncontrolling Interest [Line Items]
Common units outstanding held by common limited partners (in units) \| shares	2,023,287	2,025,287
Exchange of common units of the Operating Partnership (in units) \| shares	2,000
Conversion ratio	1
Operating Partnership [Member]
Noncontrolling Interest [Line Items]
Ownership interest	98.10%	98.00%
101 First LLC and 303 Second LLC [Member]
Noncontrolling Interest [Line Items]
Ownership interest	56.00%
Noncontrolling interest in consolidated subsidiary	$ 189,600	$ 186,400

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The number of shares issued during the period upon the conversion of units. An example of a convertible unit is an umbrella partnership real estate investment trust unit (UPREIT unit).

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