CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenue, Product and Service [Extensible List]	us-gaap:ServiceMember
REVENUES
Rental income (Note 8)	$ 218,356	$ 197,629	$ 436,989	$ 397,011
Other property income	1,067	2,863	3,762	4,683
Total revenues	219,423	200,492	440,751	401,694
EXPENSES
Property expenses	37,829	38,536	76,812	76,685
Real estate taxes	21,854	17,926	44,056	36,565
Ground leases (Note 9)	2,330	2,114	4,647	4,086
General and administrative expenses (Notes 7 and 10)	38,597	19,857	57,607	43,198
Leasing costs	1,330	2,650	2,786	4,407
Depreciation and amortization	80,085	68,252	154,455	134,387
Total expenses	182,025	149,335	340,363	299,328
OTHER (EXPENSES) INCOME
Interest income and other net investment gain (loss) (Note 10)	2,838	616	(290)	2,444
Interest expense (Note 3)	(15,884)	(11,727)	(30,328)	(22,970)
Gains on sales of depreciable operating properties	0	7,169	0	7,169
Total other (expenses) income	(13,046)	(3,942)	(30,618)	(13,357)
NET INCOME	24,352	47,215	69,770	89,009
Net income attributable to noncontrolling common units of the Operating Partnership	(367)	(871)	(1,072)	(1,571)
Net income attributable to noncontrolling interests in consolidated property partnerships	(4,367)	(4,150)	(9,263)	(8,341)
Total income attributable to noncontrolling interests	(4,734)	(5,021)	(10,335)	(9,912)
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS (UNITHOLDERS)	$ 19,618	$ 42,194	$ 59,435	$ 79,097
Net income available to common stockholders per share – basic (in dollars per share)	$ 0.17	$ 0.41	$ 0.53	$ 0.77
Net income available to common stockholders per share – diluted (in dollars per share)	$ 0.17	$ 0.41	$ 0.52	$ 0.77
Weighted average common shares outstanding – basic (in shares)	115,084,897	100,972,355	110,980,066	100,937,069
Weighted average common shares outstanding – diluted (in shares)	115,539,725	101,809,541	111,464,647	101,618,953
Kilroy Realty L.P. [Member]
REVENUES
Rental income (Note 8)	$ 218,356	$ 197,629	$ 436,989	$ 397,011
Other property income	1,067	2,863	3,762	4,683
Total revenues	219,423	200,492	440,751	401,694
EXPENSES
Property expenses	37,829	38,536	76,812	76,685
Real estate taxes	21,854	17,926	44,056	36,565
Ground leases (Note 9)	2,330	2,114	4,647	4,086
General and administrative expenses (Notes 7 and 10)	38,597	19,857	57,607	43,198
Leasing costs	1,330	2,650	2,786	4,407
Depreciation and amortization	80,085	68,252	154,455	134,387
Total expenses	182,025	149,335	340,363	299,328
OTHER (EXPENSES) INCOME
Interest income and other net investment gain (loss) (Note 10)	2,838	616	(290)	2,444
Interest expense (Note 3)	(15,884)	(11,727)	(30,328)	(22,970)
Gains on sales of depreciable operating properties	0	7,169	0	7,169
Total other (expenses) income	(13,046)	(3,942)	(30,618)	(13,357)
NET INCOME	24,352	47,215	69,770	89,009
Total income attributable to noncontrolling interests	(4,514)	(4,314)	(9,543)	(8,600)
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS (UNITHOLDERS)	$ 19,838	$ 42,901	$ 60,227	$ 80,409
Net income available to common stockholders per share – basic (in dollars per share)	$ 0.16	$ 0.41	$ 0.52	$ 0.77
Net income available to common stockholders per share – diluted (in dollars per share)	$ 0.16	$ 0.41	$ 0.52	$ 0.77
Weighted average common shares outstanding – basic (in shares)	117,098,562	102,995,642	112,997,795	102,960,599
Weighted average common shares outstanding – diluted (in shares)	117,553,390	103,832,828	113,482,376	103,642,483