CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenue, Product and Service [Extensible List]	us-gaap:ServiceMember	us-gaap:ServiceMember
REVENUES
Rental income (Note 10)	$ 224,473	$ 218,356	$ 459,129	$ 436,989
Other property income	1,510	1,067	2,500	3,762
Total revenues	225,983	219,423	461,629	440,751
EXPENSES
Property expenses	40,482	37,829	79,341	76,812
Real estate taxes	22,109	21,854	47,375	44,056
Ground leases (Note 11)	2,023	2,330	3,851	4,647
General and administrative expenses (Note 9)	24,507	38,597	46,492	57,607
Leasing costs	883	1,330	1,575	2,786
Depreciation and amortization	73,589	80,085	149,521	154,455
Total expenses	163,593	182,025	328,155	340,363
OTHER INCOME (EXPENSES)
Interest income and other net investment gain (loss) (Note 12)	1,337	2,838	2,710	(290)
Interest expense (Note 5)	(21,390)	(15,884)	(43,724)	(30,328)
Gain on sale of depreciable operating property (Note 3)	543	0	457,831	0
Total other (expenses) income	(19,510)	(13,046)	416,817	(30,618)
NET INCOME	42,880	24,352	550,291	69,770
Net income attributable to noncontrolling common units of the Operating Partnership	(354)	(367)	(5,240)	(1,072)
Net income attributable to noncontrolling interests in consolidated property partnerships	(6,687)	(4,367)	(11,581)	(9,263)
Total income attributable to noncontrolling interests	(7,041)	(4,734)	(16,821)	(10,335)
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS (UNITHOLDERS)	$ 35,839	$ 19,618	$ 533,470	$ 59,435
Net income available to common stockholders per share – basic (in dollars per share)	$ 0.30	$ 0.17	$ 4.58	$ 0.53
Net income available to common stockholders per share – diluted (in dollars per share)	$ 0.30	$ 0.17	$ 4.56	$ 0.52
Weighted average common shares outstanding – basic (in shares)	116,451,931	115,084,897	116,398,450	110,980,066
Weighted average common shares outstanding – diluted (in shares)	116,917,463	115,539,725	116,859,745	111,464,647
Kilroy Realty L.P. [Member]
Revenue, Product and Service [Extensible List]	us-gaap:ServiceMember	us-gaap:ServiceMember
REVENUES
Rental income (Note 10)	$ 224,473	$ 218,356	$ 459,129	$ 436,989
Other property income	1,510	1,067	2,500	3,762
Total revenues	225,983	219,423	461,629	440,751
EXPENSES
Property expenses	40,482	37,829	79,341	76,812
Real estate taxes	22,109	21,854	47,375	44,056
Ground leases (Note 11)	2,023	2,330	3,851	4,647
General and administrative expenses (Note 9)	24,507	38,597	46,492	57,607
Leasing costs	883	1,330	1,575	2,786
Depreciation and amortization	73,589	80,085	149,521	154,455
Total expenses	163,593	182,025	328,155	340,363
OTHER INCOME (EXPENSES)
Interest income and other net investment gain (loss) (Note 12)	1,337	2,838	2,710	(290)
Interest expense (Note 5)	(21,390)	(15,884)	(43,724)	(30,328)
Gain on sale of depreciable operating property (Note 3)	543	0	457,831	0
Total other (expenses) income	(19,510)	(13,046)	416,817	(30,618)
NET INCOME	42,880	24,352	550,291	69,770
Total income attributable to noncontrolling interests	(6,687)	(4,514)	(11,581)	(9,543)
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS (UNITHOLDERS)	$ 36,193	$ 19,838	$ 538,710	$ 60,227
Net income available to common stockholders per share – basic (in dollars per share)	$ 0.30	$ 0.16	$ 4.58	$ 0.52
Net income available to common stockholders per share – diluted (in dollars per share)	$ 0.30	$ 0.16	$ 4.56	$ 0.52
Weighted average common shares outstanding – basic (in shares)	117,602,505	117,098,562	117,549,024	112,997,795
Weighted average common shares outstanding – diluted (in shares)	118,068,037	117,553,390	118,010,319	113,482,376