Kilroy Realty (KRC) 10-K 12 Feb 21 2020 FY Annual report Financial data

Cover Page

Cover Page - USD ($)	12 Months Ended
	Dec. 31, 2020	Feb. 05, 2021	Jun. 30, 2020
Entity Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	1-12675
Entity Registrant Name	KILROY REALTY CORPORATION
Entity Central Index Key	0001025996
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Incorporation, State or Country Code	MD
Entity Tax Identification Number	95-4598246
Entity Address, Address Line One	12200 W. Olympic Boulevard
Entity Address, Address Line Two	Suite 200
Entity Address, City or Town	Los Angeles
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	90064
City Area Code	(310)
Local Phone Number	481-8400
Title of 12(b) Security	Common Stock, $.01 par value
Security Exchange Name	NYSE
Trading Symbol	KRC
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 6,728,133,187
Entity Common Stock, Shares Outstanding		116,369,096
Documents Incorporated by Reference	Portions of the Kilroy Realty Corporation’s Proxy Statement with respect to its 2021 Annual Meeting of Stockholders to be filed not later than 120 days after the end of the registrant’s fiscal year are incorporated by reference into Part III of this Form 10-K.
Kilroy Realty L.P. [Member]
Entity Information [Line Items]
Current Fiscal Year End Date	--12-31
Entity File Number	000-54005
Entity Registrant Name	KILROY REALTY, L.P.
Entity Central Index Key	0001493976
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	95-4612685
Title of 12(g) Security	Common Units Representing Limited Partnership Interests
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
REAL ESTATE ASSETS
Land and improvements	$ 1,628,848	$ 1,466,166
Buildings and improvements	6,783,092	5,866,477
Undeveloped land and construction in progress	1,778,106	2,296,130
Total real estate assets held for investment	10,190,046	9,628,773
Accumulated depreciation and amortization	(1,798,646)	(1,561,361)
Total real estate assets held for investment, net	8,391,400	8,067,412
CASH AND CASH EQUIVALENTS (Note 22)	731,991	60,044
RESTRICTED CASH (Notes 3, 4 and 22)	91,139	16,300
MARKETABLE SECURITIES (Notes 16 and 19)	27,481	27,098
CURRENT RECEIVABLES, NET (Notes 2 and 6)	12,007	26,489
DEFERRED RENT RECEIVABLES, NET (Notes 2 and 6)	386,658	337,937
DEFERRED LEASING COSTS AND ACQUISITION-RELATED INTANGIBLE ASSETS, NET (Notes 2, 3 and 5)	210,949	212,805
RIGHT OF USE GROUND LEASE ASSETS (Notes 2 and 18)	95,523	96,348
PREPAID EXPENSES AND OTHER ASSETS, NET (Note 7)	53,560	55,661
TOTAL ASSETS	10,000,708	8,900,094
LIABILITIES:
Secured debt, net (Notes 8, 9 and 19)	253,582	258,593
Unsecured debt, net (Notes 8, 9 and 19)	3,670,099	3,049,185
Unsecured line of credit (Notes 8, 9 and 19)	0	245,000
Accounts payable, accrued expenses and other liabilities (Note 18)	445,100	418,848
Ground lease liabilities (Notes 2 and 18)	97,778	98,400
Accrued dividends and distributions (Notes 13 and 27)	59,431	53,219
Deferred revenue and acquisition-related intangible liabilities, net (Notes 2, 3, 5 and 10)	128,523	139,488
Rents received in advance and tenant security deposits	68,874	66,503
Total liabilities	4,723,387	4,329,236
COMMITMENTS AND CONTINGENCIES (Note 18)
Stockholders’ Equity (Note 13):
Common stock, $.01 par value, 280,000,000 and 150,000,000 shares authorized, respectively, 116,035,827 and 106,016,287 shares issued and outstanding, respectively	1,160	1,060
Additional paid-in capital	5,131,916	4,350,917
Distributions in excess of earnings	(103,133)	(58,467)
Total stockholders’ equity	5,029,943	4,293,510
Noncontrolling Interests (Notes 2 and 11):
Common units of the Operating Partnership	49,875	81,917
Noncontrolling interests in consolidated property partnerships	197,503	195,431
Total noncontrolling interests	247,378	277,348
Total equity	5,277,321	4,570,858
TOTAL LIABILITIES AND EQUITY/CAPITAL	$ 10,000,708	$ 8,900,094

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2020	May 19, 2020	May 18, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.01			$ 0.01
Common stock, authorized (shares)	280,000,000	280,000,000	150,000,000	150,000,000
Common stock, shares issued (in shares)	116,035,827			106,016,287
Common stock, shares outstanding	116,035,827			106,016,287

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
REVENUES (Note 2):
Rental income	$ 892,306	$ 826,472	$ 656,631
Tenant reimbursements	0	0	80,982
Other property income	6,091	10,982	9,685
Revenues	898,397	837,454	747,298
EXPENSES:
Property expenses	155,118	160,037	133,787
Real estate taxes (Note 2)	92,218	78,097	70,820
Provision for bad debts (Note 2)	0	0	5,685
Ground leases (Notes 2, 5 and 18)	8,891	8,113
Ground leases (Notes 2, 5 and 18)			6,176
General and administrative expenses (Notes 15 and 19)	99,264	88,139	90,471
Leasing costs (Notes 2 and 5)	4,493	7,615
Depreciation and amortization (Notes 2 and 5)	299,308	273,130	254,281
Total expenses	659,292	615,131	561,220
OTHER (EXPENSES) INCOME:
Interest income and other net investment gain (loss) (Note 19)	3,424	4,641	(559)
Interest expense (Note 9)	(70,772)	(48,537)	(49,721)
Gains on sales of depreciable operating properties (Note 4)	35,536	36,802	142,926
Loss on early extinguishment of debt (Note 9)	0	0	(12,623)
Net gain on sales of land (Note 4)	0	0	11,825
Total other (expenses) income	(31,812)	(7,094)	91,848
NET INCOME	207,293	215,229	277,926
Net income attributable to noncontrolling common units of the Operating Partnership (Notes 2 and 11)	(2,869)	(3,766)	(5,193)
Net income attributable to noncontrolling interests in consolidated property partnerships (Notes 2 and 11)	(17,319)	(16,020)	(14,318)
Total income attributable to noncontrolling interests	(20,188)	(19,786)	(19,511)
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS (UNITHOLDERS)	$ 187,105	$ 195,443	$ 258,415
Net income available to common stockholders per share - basic (in dollars per share)	$ 1.63	$ 1.87	$ 2.56
Net income available to common stockholders per share - diluted (in dollars per share)	$ 1.63	$ 1.86	$ 2.55
Weighted average shares of common stock outstanding – basic (in shares)	113,241,341	103,200,568	99,972,359
Weighted average shares of common stock outstanding – diluted (in shares)	113,719,622	103,849,168	100,482,365
Revenue, Product and Service [Extensible List]	us-gaap:ServiceMember

CONSOLIDATED STATEMENTS OF EQUI

CONSOLIDATED STATEMENTS OF EQUITY - USD ($) $ in Thousands	Total	Total Stockholders' Equity	Common Stock [Member]	Additional Paid-in Capital [Member]	Distributions in Excess of Earnings [Member]	Noncontrolling Interests [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member]Total Stockholders' Equity	Cumulative Effect, Period of Adoption, Adjustment [Member]Distributions in Excess of Earnings [Member]
Beginning balance at Dec. 31, 2017	$ 3,960,316	$ 3,700,793	$ 986	$ 3,822,492	$ (122,685)	$ 259,523
Beginning balance (in shares) at Dec. 31, 2017			98,620,333
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	277,926	258,415			258,415	19,511
Issuance of common stock	130,693	130,693	$ 18	130,675
Issuance of common stock (in shares)			1,817,195
Issuance of share-based compensation awards	3,926	3,926		3,926
Non-cash amortization of share-based compensation	35,890	35,890		35,890
Exercise of stock options	41	41	$ 0	41
Exercise of stock options (in shares)			1,000
Settlement of restricted stock units for shares of common stock	$ 0		$ 4	(4)
Repurchase and cancellation of common stock, stock options and restricted stock (in shares)	0
Repurchase of common stock, stock options and restricted stock units	$ (16,553)	(16,553)	$ (2)	(16,551)
Repurchase of common stock, stock options and restricted stock units (in shares)			(231,800)
Settlement of restricted stock units for shares of common stock (in shares)			488,354
Exchange of common units of the Operating Partnership	0	1,962	$ 1	1,961		(1,962)
Exchange of common units of the Operating Partnership (in shares)			51,906
Contributions from noncontrolling interests in consolidated property partnerships	8,273					8,273
Distributions to noncontrolling interests in consolidated property partnerships	(11,803)					(11,803)
Adjustment for noncontrolling interest in the Operating Partnership	0	(1,477)		(1,477)		1,477
Dividends declared per share of common stock and common unit	(187,448)	(183,783)			(183,783)	(3,665)
Ending balance at Dec. 31, 2018	$ 4,201,261	3,929,907	$ 1,007	3,976,953	(48,053)	271,354	$ (3,146)	$ (3,146)	$ (3,146)
Ending balance (in shares) at Dec. 31, 2018			100,746,988
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201602Member
Net income	$ 215,229	195,443			195,443	19,786
Issuance of common stock	353,722	353,722	$ 50	353,672
Issuance of common stock (in shares)			5,000,000
Issuance of share-based compensation awards	4,664	4,664		4,664
Non-cash amortization of share-based compensation	32,813	32,813		32,813
Exercise of stock options	703	703		703
Exercise of stock options (in shares)			16,500
Settlement of restricted stock units for shares of common stock	$ 0		$ 5	(5)
Repurchase and cancellation of common stock, stock options and restricted stock (in shares)	0		(212,477)
Repurchase and cancellation of common stock, stock options and restricted stock units			$ (2)	(14,859)
Repurchase of common stock, stock options and restricted stock units	$ (14,861)	(14,861)
Settlement of restricted stock units for shares of common stock (in shares)			463,276
Exchange of common units of the Operating Partnership	0	78	$ 0	78		(78)
Exchange of common units of the Operating Partnership (in shares)			2,000
Distributions to noncontrolling interests in consolidated property partnerships	(12,952)					(12,952)
Adjustment for noncontrolling interest in the Operating Partnership	0	(3,102)		(3,102)		3,102
Dividends declared per share of common stock and common unit	(206,575)	(202,711)			(202,711)	(3,864)
Ending balance at Dec. 31, 2019	$ 4,570,858	4,293,510	$ 1,060	4,350,917	(58,467)	277,348
Ending balance (in shares) at Dec. 31, 2019	106,016,287		106,016,287
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 207,293	187,105			187,105	20,188
Issuance of common stock	721,665	721,665	$ 89	721,576
Issuance of common stock (in shares)			8,897,110
Issuance of share-based compensation awards	4,441	4,441		4,441
Non-cash amortization of share-based compensation	37,624	37,624		37,624
Settlement of restricted stock units for shares of common stock	$ 0		$ 4	(4)
Repurchase and cancellation of common stock, stock options and restricted stock (in shares)	0		(191,699)
Repurchase and cancellation of common stock, stock options and restricted stock units			$ (2)	(14,080)
Repurchase of common stock, stock options and restricted stock units	$ (14,082)	(14,082)
Settlement of restricted stock units for shares of common stock (in shares)			441,416
Exchange of common units of the Operating Partnership	0	37,640	$ 9	37,631		(37,640)
Exchange of common units of the Operating Partnership (in shares)			872,713
Distributions to noncontrolling interests in consolidated property partnerships	(15,247)					(15,247)
Adjustment for noncontrolling interest in the Operating Partnership	0	(6,189)		(6,189)		6,189
Dividends declared per share of common stock and common unit	(235,231)	(231,771)			(231,771)	(3,460)
Ending balance at Dec. 31, 2020	$ 5,277,321	$ 5,029,943	$ 1,160	$ 5,131,916	$ (103,133)	$ 247,378
Ending balance (in shares) at Dec. 31, 2020	116,035,827		116,035,827

CONSOLIDATED STATEMENTS OF EQ_2

CONSOLIDATED STATEMENTS OF EQUITY (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Stockholders' Equity [Abstract]
Dividends declared per common share (in dollars per share)	$ 1.97	$ 1.91	$ 1.79

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 207,293	$ 215,229	$ 277,926
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of real estate assets and leasing costs	290,353	268,045	249,882
Depreciation of non-real estate furniture, fixtures and equipment	8,955	5,085	4,400
Revenue reversals (recoveries) for doubtful accounts (Notes 2 and 17)	18,997	(3,433)	5,685
Non-cash amortization of share-based compensation awards (Note 15)	30,245	27,007	27,932
Non-cash amortization of deferred financing costs and net debt discounts	2,958	1,427	1,084
Non-cash amortization of net below market rents (Note 5)	(7,603)	(9,206)	(9,748)
Gains on sales of depreciable operating properties (Note 4)	(35,536)	(36,802)	(142,926)
Non-cash amortization of deferred revenue related to tenant-funded tenant improvements (Note 10)	(17,547)	(19,190)	(18,429)
Straight-line rents	(67,826)	(72,023)	(26,976)
Amortization of right of use ground lease assets (Note 2)	825	683
Loss on early extinguishment of debt (Note 9)	0	0	12,623
Gain on sale of land (Note 4)	0	0	(11,825)
Net change in other operating assets	(3,685)	(14,476)	(7,930)
Net change in other operating liabilities	28,161	24,175	48,345
Net cash provided by operating activities	455,590	386,521	410,043
CASH FLOWS FROM INVESTING ACTIVITIES:
Expenditures for development properties and undeveloped land	(486,565)	(845,464)	(489,236)
Expenditures for operating properties and other capital assets	(129,500)	(147,687)	(166,440)
Net proceeds received from dispositions (Note 4)	74,937	124,421	364,300
(Increase) decrease in acquisition-related deposits	(1,000)	0	36,000
Expenditures for acquisitions of development properties and undeveloped land (Note 3)	0	(173,291)	(311,299)
Expenditures for acquisitions of operating properties (Note 3)	0	(186,258)	(257,340)
Proceeds received from repayment of note receivable	0	0	15,100
Net cash used in investing activities	(542,128)	(1,228,279)	(808,915)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net proceeds from issuance of common stock (Note 13)	721,665	353,722	130,693
Net proceeds from the issuance of unsecured debt (Note 9)	772,297	499,390	648,537
Repayments of unsecured debt (Note 9)	(150,000)	0	(261,823)
Borrowings on unsecured revolving credit facility	190,000	1,110,000	765,000
Repayments on unsecured revolving credit facility	(435,000)	(910,000)	(690,000)
Principal payments and repayments of secured debt (Note 9)	(5,137)	(76,309)	(3,584)
Financing costs	(6,594)	(6,678)	(6,262)
Repurchase of common stock and restricted stock units (Note 15)	(14,082)	(14,556)	(16,553)
Distributions to noncontrolling interests in consolidated property partnerships	(15,247)	(12,952)	(11,803)
Dividends and distributions paid to common stockholders and common unitholders	(224,578)	(196,252)	(179,411)
Proceeds from exercise of stock options	0	703	41
Borrowings on unsecured debt	0	0	120,000
Contributions from noncontrolling interests in consolidated property partnerships	0	0	8,273
Net cash provided by financing activities	833,324	747,068	503,108
Net increase (decrease) in cash and cash equivalents and restricted cash	746,786	(94,690)	104,236
Cash and cash equivalents and restricted cash, beginning of year	76,344	171,034	66,798
Cash and cash equivalents and restricted cash, end of year	$ 823,130	$ 76,344	$ 171,034

CONSOLIDATED BALANCE SHEETS (KI

CONSOLIDATED BALANCE SHEETS (KILROY REALTY, L.P.) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
REAL ESTATE ASSETS
Land and improvements	$ 1,628,848	$ 1,466,166
Buildings and improvements	6,783,092	5,866,477
Undeveloped land and construction in progress	1,778,106	2,296,130
Total real estate assets held for investment	10,190,046	9,628,773
Accumulated depreciation and amortization	(1,798,646)	(1,561,361)
Total real estate assets held for investment, net	8,391,400	8,067,412
CASH AND CASH EQUIVALENTS (Note 23)	731,991	60,044
RESTRICTED CASH (Notes 3, 4 and 23)	91,139	16,300
MARKETABLE SECURITIES (Notes 16 and 19)	27,481	27,098
CURRENT RECEIVABLES, NET (Notes 2 and 6)	12,007	26,489
DEFERRED RENT RECEIVABLES, NET (Notes 2 and 6)	386,658	337,937
DEFERRED LEASING COSTS AND ACQUISITION-RELATED INTANGIBLE ASSETS, NET (Notes 2, 3 and 5)	210,949	212,805
RIGHT OF USE GROUND LEASE ASSETS (Notes 2 and 18)	95,523	96,348
PREPAID EXPENSES AND OTHER ASSETS, NET (Note 7)	53,560	55,661
TOTAL ASSETS	10,000,708	8,900,094
LIABILITIES:
Secured debt, net (Notes 9 and 19)	253,582	258,593
Unsecured debt, net (Notes 9 and 19)	3,670,099	3,049,185
Unsecured line of credit (Notes 9 and 19)	0	245,000
Accounts payable, accrued expenses and other liabilities (Note 18)	445,100	418,848
Ground lease liabilities (Notes 2 and 18)	97,778	98,400
Accrued distributions (Notes 14 and 27)	59,431	53,219
Deferred revenue and acquisition-related intangible liabilities, net (Notes 2, 3, 5 and 10)	128,523	139,488
Rents received in advance and tenant security deposits	68,874	66,503
Total liabilities	4,723,387	4,329,236
COMMITMENTS AND CONTINGENCIES (Note 18)
Partners’ Capital:
TOTAL LIABILITIES AND EQUITY/CAPITAL	10,000,708	8,900,094
Kilroy Realty L.P. [Member]
REAL ESTATE ASSETS
Land and improvements	1,628,848	1,466,166
Buildings and improvements	6,783,092	5,866,477
Undeveloped land and construction in progress	1,778,106	2,296,130
Total real estate assets held for investment	10,190,046	9,628,773
Accumulated depreciation and amortization	(1,798,646)	(1,561,361)
Total real estate assets held for investment, net	8,391,400	8,067,412
CASH AND CASH EQUIVALENTS (Note 23)	731,991	60,044
RESTRICTED CASH (Notes 3, 4 and 23)	91,139	16,300
MARKETABLE SECURITIES (Notes 16 and 19)	27,481	27,098
CURRENT RECEIVABLES, NET (Notes 2 and 6)	12,007	26,489
DEFERRED RENT RECEIVABLES, NET (Notes 2 and 6)	386,658	337,937
DEFERRED LEASING COSTS AND ACQUISITION-RELATED INTANGIBLE ASSETS, NET (Notes 2, 3 and 5)	210,949	212,805
RIGHT OF USE GROUND LEASE ASSETS (Notes 2 and 18)	95,523	96,348
PREPAID EXPENSES AND OTHER ASSETS, NET (Note 7)	53,560	55,661
TOTAL ASSETS	10,000,708	8,900,094
LIABILITIES:
Secured debt, net (Notes 9 and 19)	253,582	258,593
Unsecured debt, net (Notes 9 and 19)	3,670,099	3,049,185
Unsecured line of credit (Notes 9 and 19)	0	245,000
Accounts payable, accrued expenses and other liabilities (Note 18)	445,100	418,848
Ground lease liabilities (Notes 2 and 18)	97,778	98,400
Accrued distributions (Notes 14 and 27)	59,431	53,219
Deferred revenue and acquisition-related intangible liabilities, net (Notes 2, 3, 5 and 10)	128,523	139,488
Rents received in advance and tenant security deposits	68,874	66,503
Total liabilities	4,723,387	4,329,236
COMMITMENTS AND CONTINGENCIES (Note 18)
Partners’ Capital:
Common units, 116,035,827 and 106,016,287 held by the general partner and 1,150,574 and 2,023,287 held by common limited partners issued and outstanding, respectively (Note 14)	5,079,818	4,369,758
Total partners’ capital	5,079,818	4,369,758
Noncontrolling interests in consolidated property partnerships and subsidiaries (Notes 2 and 12)	197,503	201,100
Total capital	5,277,321	4,570,858
TOTAL LIABILITIES AND EQUITY/CAPITAL	$ 10,000,708	$ 8,900,094

CONSOLIDATED BALANCE SHEETS (_2

CONSOLIDATED BALANCE SHEETS (KILROY REALTY, L.P.) (Parenthetical) - Common units [Member] - Kilroy Realty L.P. [Member] - shares	Dec. 31, 2020	Dec. 31, 2019
General partner, units issued (in units)	116,035,827	106,016,287
General partner, units outstanding (in units)	116,035,827	106,016,287
Limited partner, units issued (in units)	1,150,574	2,023,287
Limited partner, units outstanding (in units)	1,150,574	2,023,287

CONSOLIDATED STATEMENTS OF OP_2

CONSOLIDATED STATEMENTS OF OPERATIONS (KILROY REALTY, L.P.) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
REVENUES (Note 2):
Rental income	$ 892,306	$ 826,472	$ 656,631
Tenant reimbursements	0	0	80,982
Other property income	6,091	10,982	9,685
Revenues	898,397	837,454	747,298
EXPENSES:
Property expenses	155,118	160,037	133,787
Real estate taxes (Note 2)	92,218	78,097	70,820
Provision for bad debts (Note 2)	0	0	5,685
Ground leases (Notes 2, 5 and 18)	8,891	8,113
Ground leases (Notes 2, 5 and 18)			6,176
General and administrative expenses (Notes 15 and 19)	99,264	88,139	90,471
Leasing costs (Notes 2 and 5)	4,493	7,615
Depreciation and amortization (Notes 2 and 5)	299,308	273,130	254,281
Total expenses	659,292	615,131	561,220
OTHER (EXPENSES) INCOME:
Interest income and other net investment gain (loss) (Note 19)	3,424	4,641	(559)
Interest expense (Note 9)	(70,772)	(48,537)	(49,721)
Gains on sales of depreciable operating properties (Note 4)	35,536	36,802	142,926
Loss on early extinguishment of debt (Note 9)	0	0	(12,623)
Net gain on sales of land (Note 4)	0	0	11,825
Total other (expenses) income	(31,812)	(7,094)	91,848
NET INCOME	207,293	215,229	277,926
Net income attributable to noncontrolling interests in consolidated property partnerships and subsidiaries (Notes 2 and 12)	(20,188)	(19,786)	(19,511)
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS (UNITHOLDERS)	$ 187,105	$ 195,443	$ 258,415
Net income available to common unitholders per unit - basic (in dollars per unit)	$ 1.63	$ 1.87	$ 2.56
Net income available to common unitholders per unit - diluted (in dollars per unit)	$ 1.63	$ 1.86	$ 2.55
Weighted average common units outstanding - basic (in shares)	113,241,341	103,200,568	99,972,359
Weighted average common units outstanding - diluted (in shares)	113,719,622	103,849,168	100,482,365
Revenue, Product and Service [Extensible List]	us-gaap:ServiceMember
Kilroy Realty L.P. [Member]
REVENUES (Note 2):
Rental income	$ 892,306	$ 826,472	$ 656,631
Tenant reimbursements	0	0	80,982
Other property income	6,091	10,982	9,685
Revenues	898,397	837,454	747,298
EXPENSES:
Property expenses	155,118	160,037	133,787
Real estate taxes (Note 2)	92,218	78,097	70,820
Provision for bad debts (Note 2)	0	0	5,685
Ground leases (Notes 2, 5 and 18)	8,891	8,113
Ground leases (Notes 2, 5 and 18)			6,176
General and administrative expenses (Notes 15 and 19)	99,264	88,139	90,471
Leasing costs (Notes 2 and 5)	4,493	7,615
Depreciation and amortization (Notes 2 and 5)	299,308	273,130	254,281
Total expenses	659,292	615,131	561,220
OTHER (EXPENSES) INCOME:
Interest income and other net investment gain (loss) (Note 19)	3,424	4,641	(559)
Interest expense (Note 9)	(70,772)	(48,537)	(49,721)
Gains on sales of depreciable operating properties (Note 4)	35,536	36,802	142,926
Loss on early extinguishment of debt (Note 9)	0	0	(12,623)
Net gain on sales of land (Note 4)	0	0	11,825
Total other (expenses) income	(31,812)	(7,094)	91,848
NET INCOME	207,293	215,229	277,926
Net income attributable to noncontrolling interests in consolidated property partnerships and subsidiaries (Notes 2 and 12)	(17,684)	(16,491)	(14,716)
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS (UNITHOLDERS)	$ 189,609	$ 198,738	$ 263,210
Net income available to common unitholders per unit - basic (in dollars per unit)	$ 1.63	$ 1.87	$ 2.56
Net income available to common unitholders per unit - diluted (in dollars per unit)	$ 1.62	$ 1.86	$ 2.55
Weighted average common units outstanding - basic (in shares)	115,095,506	105,223,975	102,025,276
Weighted average common units outstanding - diluted (in shares)	115,573,787	105,872,575	102,535,282
Revenue, Product and Service [Extensible List]	us-gaap:ServiceMember

CONSOLIDATED STATEMENTS OF CAPI

CONSOLIDATED STATEMENTS OF CAPITAL (KILROY REALTY, L.P.) - USD ($) $ in Thousands	3 Months Ended				12 Months Ended
	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 83,452	$ 45,418	$ 77,922	$ 41,794	$ 207,293	$ 215,229	$ 277,926
Non-cash amortization of share-based compensation					37,624	32,813	35,890
Settlement of restricted stock units					0	0	0
Distributions to noncontrolling interests in consolidated property partnerships					(15,247)	(12,952)	$ (11,803)
Accounting Standards Update [Extensible List]							us-gaap:AccountingStandardsUpdate201602Member
Noncontrolling Interest In Consolidated Subsidiaries [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income					20,188	19,786	$ 19,511
Distributions to noncontrolling interests in consolidated property partnerships					(15,247)	(12,952)	(11,803)
Kilroy Realty L.P. [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		4,570,858		4,201,261	4,570,858	4,201,261	3,960,316
Net income	83,452	45,418	77,922	41,794	207,293	215,229	277,926
Issuance of common units					721,665	353,722	130,693
Issuance of share-based compensation awards					4,441	4,664	3,926
Non-cash amortization of share-based compensation					37,624	32,813	35,890
Exercise of stock options						703	41
Settlement of restricted stock units					0	0	0
Repurchase of common units and restricted stock units					(14,082)	(14,861)	(16,553)
Contributions from noncontrolling interest in consolidated property partnerships							8,273
Distributions to noncontrolling interests in consolidated property partnerships					(15,247)	(12,952)	(11,803)
Distributions declared per common unit					(235,231)	(206,575)	(187,448)
Ending balance	5,277,321		4,570,858		5,277,321	4,570,858	4,201,261
Kilroy Realty L.P. [Member] | Partners Capital Common Unit [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		$ 4,369,758		$ 4,003,700	$ 4,369,758	$ 4,003,700	$ 3,773,941
Beginning balance (in units)		108,039,574		102,772,275	108,039,574	102,772,275	100,697,526
Net income					$ 189,609	$ 198,738	$ 263,210
Issuance of common units					$ 721,665	$ 353,722	$ 130,693
Issuance of common units (in units)					8,897,110	5,000,000	1,817,195
Issuance of share-based compensation awards					$ 4,441	$ 4,664	$ 3,926
Non-cash amortization of share-based compensation					$ 37,624	32,813	35,890
Exercise of stock options						$ 703	$ 41
Exercise of stock options (in units)						16,500	1,000
Settlement of restricted stock units (in units)					441,416	463,276	488,354
Repurchase of common units and restricted stock units					$ (14,082)	$ (14,861)	$ (16,553)
Repurchase of common units and restricted stock units (in units)					(191,699)	(212,477)	(231,800)
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests					$ 6,034
Distributions declared per common unit					(235,231)	$ (206,575)	$ (187,448)
Ending balance	$ 5,079,818		$ 4,369,758		$ 5,079,818	$ 4,369,758	$ 4,003,700
Ending balance (in units)	117,186,401		108,039,574		117,186,401	108,039,574	102,772,275
Kilroy Realty L.P. [Member] | Noncontrolling Interest In Consolidated Subsidiaries [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		$ 201,100		$ 197,561	$ 201,100	$ 197,561	$ 186,375
Net income					17,684	16,491	14,716
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests					(6,034)
Contributions from noncontrolling interest in consolidated property partnerships							8,273
Distributions to noncontrolling interests in consolidated property partnerships					(15,247)	(12,952)	(11,803)
Ending balance	$ 197,503		$ 201,100		$ 197,503	201,100	197,561
Cumulative Effect, Period of Adoption, Adjustment [Member] | Kilroy Realty L.P. [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance				(3,146)		(3,146)
Ending balance							(3,146)
Cumulative Effect, Period of Adoption, Adjustment [Member] | Kilroy Realty L.P. [Member] | Partners Capital Common Unit [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance				$ (3,146)		$ (3,146)
Ending balance							$ (3,146)

CONSOLIDATED STATEMENTS OF CA_2

CONSOLIDATED STATEMENTS OF CAPITAL (KILROY REALTY, L.P.) - Parenthetical - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Kilroy Realty L.P. [Member]
Distributions declared per common unit (in dollars per units)	$ 1.97	$ 1.91	$ 1.79

CONSOLIDATED STATEMENTS OF CA_3

CONSOLIDATED STATEMENTS OF CASH FLOWS (KILROY REALTY, L.P.) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 207,293	$ 215,229	$ 277,926
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of real estate assets and leasing costs	290,353	268,045	249,882
Depreciation of non-real estate furniture, fixtures and equipment	8,955	5,085	4,400
Revenue reversals (recoveries) for doubtful accounts (Notes 2 and 17)	18,997	(3,433)	5,685
Non-cash amortization of share-based compensation awards (Note 15)	30,245	27,007	27,932
Non-cash amortization of deferred financing costs and net debt discounts	2,958	1,427	1,084
Non-cash amortization of net below market rents (Note 5)	(7,603)	(9,206)	(9,748)
Gains on sales of depreciable operating properties (Note 4)	(35,536)	(36,802)	(142,926)
Non-cash amortization of deferred revenue related to tenant-funded tenant improvements (Note 10)	(17,547)	(19,190)	(18,429)
Straight-line rents	(67,826)	(72,023)	(26,976)
Amortization of right of use ground lease assets (Note 2)	825	683
Net change in other operating assets	(3,685)	(14,476)	(7,930)
Net change in other operating liabilities	28,161	24,175	48,345
Loss on early extinguishment of debt (Note 9)	0	0	12,623
Gain on sale of land (Note 4)	0	0	(11,825)
Net cash provided by operating activities	455,590	386,521	410,043
CASH FLOWS FROM INVESTING ACTIVITIES:
Expenditures for development properties and undeveloped land	(486,565)	(845,464)	(489,236)
Expenditures for operating properties and other capital assets	(129,500)	(147,687)	(166,440)
Net proceeds received from dispositions (Note 4)	74,937	124,421	364,300
(Increase) decrease in acquisition-related deposits	(1,000)	0	36,000
Expenditures for acquisitions of development properties and undeveloped land (Note 3)	0	(173,291)	(311,299)
Expenditures for acquisitions of operating properties (Note 3)	0	(186,258)	(257,340)
Proceeds received from repayment of note receivable	0	0	15,100
Net cash used in investing activities	(542,128)	(1,228,279)	(808,915)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net proceeds from issuance of common units (Note 14)	721,665	353,722	130,693
Net proceeds from the issuance of unsecured debt (Note 9)	772,297	499,390	648,537
Repayments of unsecured debt (Note 9)	(150,000)	0	(261,823)
Borrowings on unsecured revolving credit facility	190,000	1,110,000	765,000
Repayments on unsecured revolving credit facility	(435,000)	(910,000)	(690,000)
Principal payments and repayments of secured debt (Note 9)	(5,137)	(76,309)	(3,584)
Financing costs	(6,594)	(6,678)	(6,262)
Repurchase of common units and restricted stock units (Note 15)	(14,082)	(14,556)	(16,553)
Distributions to noncontrolling interests in consolidated property partnerships	(15,247)	(12,952)	(11,803)
Distributions paid to common unitholders	(224,578)	(196,252)	(179,411)
Proceeds from exercise of stock options	0	703	41
Borrowings on unsecured debt	0	0	120,000
Contributions from noncontrolling interests in consolidated property partnerships	0	0	8,273
Net cash provided by financing activities	833,324	747,068	503,108
Net increase (decrease) in cash and cash equivalents and restricted cash	746,786	(94,690)	104,236
Cash and cash equivalents and restricted cash, beginning of year	76,344	171,034	66,798
Cash and cash equivalents and restricted cash, end of year	823,130	76,344	171,034
Kilroy Realty L.P. [Member]
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	207,293	215,229	277,926
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of real estate assets and leasing costs	290,353	268,045	249,882
Depreciation of non-real estate furniture, fixtures and equipment	8,955	5,085	4,400
Revenue reversals (recoveries) for doubtful accounts (Notes 2 and 17)	18,997	(3,433)	5,685
Non-cash amortization of share-based compensation awards (Note 15)	30,245	27,007	27,932
Non-cash amortization of deferred financing costs and net debt discounts	2,958	1,427	1,084
Non-cash amortization of net below market rents (Note 5)	(7,603)	(9,206)	(9,748)
Gains on sales of depreciable operating properties (Note 4)	(35,536)	(36,802)	(142,926)
Non-cash amortization of deferred revenue related to tenant-funded tenant improvements (Note 10)	(17,547)	(19,190)	(18,429)
Straight-line rents	(67,826)	(72,023)	(26,976)
Amortization of right of use ground lease assets (Note 2)	825	683
Net change in other operating assets	(3,685)	(14,476)	(7,930)
Net change in other operating liabilities	28,161	24,175	48,345
Loss on early extinguishment of debt (Note 9)	0	0	12,623
Gain on sale of land (Note 4)	0	0	(11,825)
Net cash provided by operating activities	455,590	386,521	410,043
CASH FLOWS FROM INVESTING ACTIVITIES:
Expenditures for development properties and undeveloped land	(486,565)	(845,464)	(489,236)
Expenditures for operating properties and other capital assets	(129,500)	(147,687)	(166,440)
Net proceeds received from dispositions (Note 4)	74,937	124,421	364,300
(Increase) decrease in acquisition-related deposits	(1,000)	0	36,000
Expenditures for acquisitions of development properties and undeveloped land (Note 3)	0	(173,291)	(311,299)
Expenditures for acquisitions of operating properties (Note 3)	0	(186,258)	(257,340)
Proceeds received from repayment of note receivable	0	0	15,100
Net cash used in investing activities	(542,128)	(1,228,279)	(808,915)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net proceeds from issuance of common units (Note 14)	721,665	353,722	130,693
Net proceeds from the issuance of unsecured debt (Note 9)	772,297	499,390	648,537
Repayments of unsecured debt (Note 9)	(150,000)	0	(261,823)
Borrowings on unsecured revolving credit facility	190,000	1,110,000	765,000
Repayments on unsecured revolving credit facility	(435,000)	(910,000)	(690,000)
Principal payments and repayments of secured debt (Note 9)	(5,137)	(76,309)	(3,584)
Financing costs	(6,594)	(6,678)	(6,262)
Repurchase of common units and restricted stock units (Note 15)	(14,082)	(14,556)	(16,553)
Distributions to noncontrolling interests in consolidated property partnerships	(15,247)	(12,952)	(11,803)
Distributions paid to common unitholders	(224,578)	(196,252)	(179,411)
Proceeds from exercise of stock options	0	703	41
Borrowings on unsecured debt	0	0	120,000
Contributions from noncontrolling interests in consolidated property partnerships	0	0	8,273
Net cash provided by financing activities	833,324	747,068	503,108
Net increase (decrease) in cash and cash equivalents and restricted cash	746,786	(94,690)	104,236
Cash and cash equivalents and restricted cash, beginning of year	76,344	171,034	66,798
Cash and cash equivalents and restricted cash, end of year	$ 823,130	$ 76,344	$ 171,034

Organization and Ownership

Organization and Ownership	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Ownership	Organization and Ownership Kilroy Realty Corporation (the “Company”) is a self-administered real estate investment trust (“REIT”) active in premier office and mixed-use submarkets along the West Coast. We own, develop, acquire and manage real estate assets, consisting primarily of Class A properties in the coastal regions of Greater Los Angeles, San Diego County, the San Francisco Bay Area and Greater Seattle, which we believe have strategic advantages and strong barriers to entry. Class A real estate encompasses attractive and efficient buildings of high quality that are attractive to tenants, are well-designed and constructed with above-average material, workmanship and finishes and are well-maintained and managed. We qualify as a REIT under the Internal Revenue Code of 1986, as amended (the “Code”). The Company’s common stock is publicly traded on the New York Stock Exchange (“NYSE”) under the ticker symbol “KRC.” We own our interests in all of our real estate assets through Kilroy Realty, L.P. (the “Operating Partnership”). We generally conduct substantially all of our operations through the Operating Partnership. Unless stated otherwise or the context indicates otherwise, the terms “Kilroy Realty Corporation” or the “Company,” “we,” “our,” and “us” refer to Kilroy Realty Corporation and its consolidated subsidiaries and the term “Operating Partnership” refers to Kilroy Realty, L.P. and its consolidated subsidiaries. The descriptions of our business, employees, and properties apply to both the Company and the Operating Partnership. Our stabilized portfolio of operating properties was comprised of the following properties at December 31, 2020: Number of Rentable Number of Percentage Occupied (unaudited) (1) Percentage Leased Stabilized Office Properties (2) 117 14,620,166 447 91.2 % 94.3 % _______________________ (1) Represents physical and economic occupancy. (2) Includes stabilized life science and retail space. Number of Projects Number of Units 2020 Average Occupancy Stabilized Residential Properties 2 808 72.0 % Our stabilized portfolio includes all of our properties with the exception of development and redevelopment properties currently committed for construction, under construction, or in the tenant improvement phase, undeveloped land and real estate assets held for sale. We define redevelopment properties as those properties for which we expect to spend significant development and construction costs on the existing or acquired buildings pursuant to a formal plan, the intended result of which is a higher economic return on the property. We define properties in the tenant improvement phase as office and life science properties that we are developing or redeveloping where the project has reached cold shell condition and is ready for tenant improvements, which may require additional major base building construction before being placed in service. Projects in the tenant improvement phase are added to our stabilized portfolio once the project reaches the earlier of 95% occupancy or one year from the date of the cessation of major base building construction activities. Costs capitalized to construction in progress for development and redevelopment properties are transferred to land and improvements, buildings and improvements, and deferred leasing costs on our consolidated balance sheets at the historical cost of the property as the projects or phases of projects are placed in service. During the year ended December 31, 2020, we added four development projects to our stabilized portfolio consisting of 750,370 square feet of office space in San Francisco, California, 361,388 square feet of office space in Hollywood, California, 95,871 square feet of retail space and 608 residential units in San Diego, California. As of December 31, 2020, the following properties were excluded from our stabilized portfolio. We did not have any redevelopment properties or properties held for sale at December 31, 2020. Number of Estimated Rentable Square Feet (1) (unaudited) In-process development projects - tenant improvement 3 1,080,000 In-process development projects - under construction (2) 3 856,000 ____________________ (1) Estimated rentable square feet upon completion. (2) In addition to the estimated office and life science rentable square feet noted above, development projects under construction also include 193 residential units. Our stabilized portfolio also excludes our future development pipeline, which as of December 31, 2020 was comprised of five future development sites, representing approximately 61 gross acres of undeveloped land. As of December 31, 2020, all of our properties and development projects were owned and all of our business was conducted in the state of California with the exception of eight stabilized office properties, one development project in the tenant improvement phase and one future development project located in the state of Washington. All of our properties and development projects are 100% owned, excluding four office properties owned by three consolidated property partnerships. Two of the three consolidated property partnerships, 100 First Street Member, LLC (“100 First LLC”) and 303 Second Street Member, LLC (“303 Second LLC”), each owned one office property in San Francisco, California through subsidiary REITs. As of December 31, 2020, the Company owned a 56% common equity interest in both 100 First LLC and 303 Second LLC. The third consolidated property partnership, Redwood City Partners, LLC (“Redwood LLC”) owned two office properties in Redwood City, California. As of December 31, 2020, the Company owned an approximate 93% common equity interest in Redwood LLC. The remaining interests in all three property partnerships were owned by unrelated third parties. As of December 31, 2020, the Company owned an approximate 99.0% common general partnership interest in the Operating Partnership. The remaining approximate 1.0% common limited partnership interest in the Operating Partnership as of December 31, 2020 was owned by non-affiliated investors and certain of our executive officers and directors. Both the general and limited common partnership interests in the Operating Partnership are denominated in common units. Generally, the number of common units held by the Company is equivalent to the number of outstanding shares of the Company’s common stock, and the rights of all the common units to quarterly distributions and payments in liquidation mirror those of the Company’s common stockholders. The common limited partners have certain redemption rights as provided in the Operating Partnership’s Seventh Amended and Restated Agreement of Limited Partnership, as amended, the “Partnership Agreement”. With the exception of the Operating Partnership and our consolidated property partnerships, all of our subsidiaries are wholly-owned.

Basis of Presentation and Signi

Basis of Presentation and Significant Accounting Policies	12 Months Ended
	Dec. 31, 2020
Basis of Presentation and Significant Accounting Policies [Abstract]
Basis of Presentation and Significant Accounting Policies	Basis of Presentation and Significant Accounting Policies Basis of Presentation The consolidated financial statements of the Company include the consolidated financial position and results of operations of the Company, the Operating Partnership, 303 Second LLC, 100 First LLC, Redwood LLC and all of our wholly-owned and controlled subsidiaries. The consolidated financial statements of the Operating Partnership include the consolidated financial position and results of operations of the Operating Partnership, 303 Second LLC, 100 First LLC, Redwood LLC and all of our wholly-owned and controlled subsidiaries. All intercompany balances and transactions have been eliminated in the consolidated financial statements. Partially Owned Entities and Variable Interest Entities At December 31, 2020 the consolidated financial statements of the Company included two VIEs in addition to the Operating Partnership: 100 First LLC and 303 Second LLC. At December 31, 2020, the Company and the Operating Partnership were determined to be the primary beneficiaries of these two VIEs since we had the ability to control the activities that most significantly impact each of the VIEs’ economic performance. As of December 31, 2020, the two VIEs’ total assets, liabilities and noncontrolling interests included on our consolidated balance sheet were approximately $469.3 million (of which $394.6 million related to real estate held for investment), approximately $33.9 million and approximately $191.9 million, respectively. Revenues, income and net assets generated by 100 First LLC and 303 Second LLC may only be used to settle their contractual obligations, which primarily consist of operating expenses, capital expenditures and required distributions. At December 31, 2019, the consolidated financial statements of the Company included four VIEs in addition to the Operating Partnership: two of the consolidated property partnerships, 100 First LLC and 303 Second LLC, and two entities established during the fourth quarter of 2019 to facilitate a Section 1031 Exchange. At December 31, 2019, the Company and the Operating Partnership were determined to be the primary beneficiaries of these four VIEs since we had the ability to control the activities that most significantly impact each of the VIEs’ economic performance. At December 31, 2019, the four VIEs’ total assets, liabilities and noncontrolling interests included on our consolidated balance sheet were approximately $676.7 million (of which $598.0 million related to real estate held for investment on our consolidated balance sheet), approximately $40.1 million and approximately $189.6 million, respectively. Our accounting policy is to consolidate entities in which we have a controlling financial interest and significant decision making control over the entity's operations. In determining whether we have a controlling financial interest in a partially owned entity and the requirement to consolidate the accounts of that entity, we consider factors such as ownership interest, board representation, management representation, size of our investment (including loans), authority to control decisions, and contractual and substantive participating rights of the members. In addition to evaluating control rights, we consolidate entities in which the other members have no substantive kick-out rights to remove the Company as the managing member. Entities in which the equity investors do not have sufficient equity at risk to finance their endeavors without additional financial support or the holders of the equity investment at risk do not have a controlling financial interest are VIEs. We evaluate whether an entity is a VIE and whether we are the primary beneficiary. We are deemed to be the primary beneficiary of a VIE when we have the power to direct the activities of the VIE that most significantly impact the VIEs’ economic performance and the obligation to absorb losses or receive benefits that could potentially be significant to the VIE. If the requirements for consolidation are not met, the Company would account for investments under the equity method of accounting if we have the ability to exercise significant influence over the entity. Equity method investments would be initially recorded at cost and subsequently adjusted for our share of net income or loss and cash contributions and distributions each period. The Company did not have any equity method investments at December 31, 2020 or 2019. Accounting Pronouncements Adopted January 1, 2020 ASU No. 2016-13 “Financial Instruments - Credit Losses (Topic 326)” Effective January 1, 2020, we adopted Financial Accounting Standards Board (“FASB”) FASB Accounting Standards Update (“ASU”) No. 2016-13 (“ASU 2016-13”), which amends the accounting for credit losses for certain financial instruments. Under the new guidance, an entity recognizes its estimate of expected credit losses as an allowance, which the FASB believes will result in more timely recognition of such losses. In November 2018, the FASB released ASU No. 2018-19 “Codification Improvements to Topic 326, Financial Instruments - Credit Losses.” This ASU clarifies that receivables arising from operating leases are not within the scope of Subtopic 326-20 “Financial Instruments – Credit Losses.” Instead, impairment of receivables arising from operating leases should be accounted for under Subtopic 842-30 “Leases – Lessor.” The adoption did not have a material impact on our consolidated financial statements or notes to our consolidated financial statements. ASU No. 2018-13 “Fair Value Measurement (Topic 820)” Effective January 1, 2020, we adopted FASB ASU No. 2018-13 (“ASU 2018-13”), which amends the disclosure requirements for fair value measurements. The amendments in ASU 2018-13 include new, modified and eliminated disclosure requirements and are the result of a broader disclosure project called FASB Concepts Statement, Conceptual Framework for Financial Reporting - Chapter 8: Notes to Financial Statements (the “Concepts Statement”), which the FASB finalized on August 28, 2018. The FASB used the guidance in the Concepts Statement to improve the effectiveness of Topic 820’s disclosure requirements. The adoption did not have a material impact on our consolidated financial statements or notes to our consolidated financial statements. ASU No. 2018-15 “Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40)” Effective January 1, 2020, we adopted FASB ASU No. 2018-15 (“ASU 2018-15”), which amends a customer’s accounting for implementation costs incurred in a cloud computing arrangement that is a service contract. ASU 2018-15 aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). The adoption did not have a material impact on our consolidated financial statements or notes to our consolidated financial statements. COVID-19 Lease Modification Accounting Relief The global impact of the COVID-19 pandemic continues to evolve rapidly. Both of the states where we own properties and/or have development projects (i.e., California and Washington), have reacted to the COVID-19 pandemic by instituting quarantines, restrictions on travel, “shelter in place” rules, restrictions on types of business that may continue to operate and/or restrictions on types of construction projects that may continue. These restrictions have impacted our business, as well as that of our tenants. Due to the business disruptions and challenges severely affecting the global economy caused by the COVID-19 pandemic, many lessors may be required to provide rent deferrals and other lease concessions to lessees. While the lease modification guidance in Accounting Standards Codification (“ASC”) Topic 842 (“Topic 842”) addresses routine changes to lease terms resulting from negotiations between the lessee and the lessor, this guidance did not contemplate concessions being so rapidly executed to address the sudden liquidity constraints of some lessees arising from the COVID-19 pandemic and restrictions intended to prevent its spread. In April 2020, the FASB staff issued a question and answer document (the “Lease Modification Q&A”) focused on the application of lease accounting guidance to lease concessions provided as a result of the COVID-19 pandemic. Under existing lease guidance, the Company would have to determine, on a lease by lease basis, if a lease concession was the result of a new arrangement reached with the tenant (treated within the lease modification accounting framework) or if a lease concession was under the enforceable rights and obligations within the existing lease agreement (precluded from applying the lease modification accounting framework). The Lease Modification Q&A allows the Company, if certain criteria have been met, to bypass the lease by lease analysis, and instead elect to either apply the lease modification accounting framework or not, with such election applied consistently to leases with similar characteristics and similar circumstances. The Company has elected to apply such relief and availed itself of the election to avoid performing a lease by lease analysis. In addition, the Company has elected to apply the lease modification accounting framework consistently to leases within the property types in which it invests, specifically office, life science, residential and retail properties. Significant Accounting Policies Revenue Recognition Rental revenue for office, life science and retail operating properties is our principal source of revenue. We recognize revenue from base rent, additional rent (which consists of amounts due from tenants for common area maintenance, real estate taxes, and other recoverable costs), parking and other lease-related revenue once all of the following criteria are met: (i) the agreement has been fully executed and delivered, (ii) services have been rendered, (iii) the amount is fixed or determinable and (iv) payment has been received or the collectability of the amount due is probable. Lease termination fees are amortized over the remaining lease term, if applicable. If there is no remaining lease term, they are recognized when received and realized. Minimum annual rental revenues are recognized in rental revenues on a straight-line basis over the non-cancellable term of the related lease. Base Rent The timing of when we commence rental revenue recognition for office, life science and retail properties depends largely on our conclusion as to whether the Company or the tenant is the owner for accounting purposes of tenant improvements at the leased property. When we conclude that we are the owner of tenant improvements for accounting purposes, we record the cost to construct the tenant improvements as an asset and commence rental revenue recognition when the tenant takes possession of or controls the finished space, which is generally when tenant improvements being recorded as our assets are substantially complete. In certain instances, when we conclude that the tenant is the owner of certain tenant improvements for accounting purposes, rental revenue recognition begins when the tenant takes possession or controls the physical use of the leased space, which may occur in phases or for an entire building or project. The determination of who owns the tenant improvements is made on a lease-by-lease basis and has a significant effect on the timing of commencement of revenue recognition. When we conclude that the Company is the owner of tenant improvements for accounting purposes, we record the cost to construct the tenant improvements, including costs paid for or reimbursed by the tenants, as a capital asset. For these tenant-funded tenant improvements, we record the amount funded by or reimbursed by tenants as deferred revenue, which is amortized and recognized as rental income on a straight-line basis over the term of the related lease. When we conclude that the tenant is the owner of certain tenant improvements for accounting purposes, we record our contribution towards those tenant-owned improvements as a lease incentive, which is included in deferred leasing costs and acquisition-related intangible assets, net on our consolidated balance sheets and amortized as a reduction to rental revenue on a straight-line basis over the term of the related lease. For residential properties, we commence revenue recognition upon lease commencement. Residential rental revenue is recognized on a straight-line basis over the term of the related lease, net of any concessions. Additional Rent - Reimbursements from Tenants Additional rent, consisting of amounts due from tenants for common area maintenance, real estate taxes and other recoverable costs, are recognized in rental income in the period the recoverable costs are incurred. Prior to the adoption of Topic 842 on January 1, 2019, such amounts were recognized in revenue as tenant reimbursements. Additional rent where we pay the associated costs directly to third-party vendors and are reimbursed by our tenants are recognized and recorded on a gross basis, with the corresponding expense recognized in property expenses or real estate taxes. Prior to the adoption of Topic 842, recoverable costs were generally recognized and recorded on a gross basis when we were the primary obligor with respect to purchasing goods and services from third-party suppliers, had discretion in selecting the supplier, and had credit risk. Other Property Income Other property income primarily includes amounts recorded in connection with transient daily parking, tenant bankruptcy settlement payments, broken deal income and property damage settlement related payments. Other property income also includes miscellaneous income from tenants, restoration fees and fees for late rental payments. Amounts recorded within other property income fall within the scope of Topic 606 and are recognized as revenue at the point in time when control of the goods or services transfers to the customer and our performance obligation is satisfied. Prior to the adoption of Topic 842 on January 1, 2019, other property income primarily included amounts recorded in connection with lease terminations, tenant bankruptcy settlement payments, broken deal income and property damage settlement payments. Uncollectible Lease Receivables and Allowances for Tenant and Deferred Rent Receivables We carry our current and deferred rent receivables net of allowances for amounts that may not be collected. Prior to the adoption of Topic 842 on January 1, 2019, the allowances were increased or decreased through provision for bad debts on our consolidated statements of operations. Upon the adoption of Topic 842 on January 1, 2019, the allowances are increased or decreased through rental income, and our determination of the adequacy of the Company’s allowances for tenant receivables includes a binary assessment of whether or not substantially all of the amounts due under a tenant’s lease agreement are probable of collection. Such assessment involves using a methodology that incorporates a specific identification analysis and an aging analysis and considers the current economic and business environment. This determination requires significant judgment and estimates about matters that are uncertain at the time the estimates are made, including the creditworthiness of specific tenants, specific industry trends and conditions, and general economic trends and conditions. For leases that are deemed probable of collection, revenue continues to be recorded on a straight-line basis over the lease term. For leases that are deemed not probable of collection, revenue is recorded as the lesser of (i) the amount which would be recognized on a straight-line basis or (ii) cash that has been received from the tenant, including deferred revenue, with any tenant and deferred rent receivable balances charged as a direct write-off against rental income in the period of the change in the collectability determination. For tenant and deferred rent receivables associated with leases whose rents are deemed probable of collection under Topic 842, we may record an allowance under other authoritative GAAP using a methodology that incorporates a specific identification analysis and an aging analysis and considers the current economic and business environment. This determination requires significant judgment and estimates about matters that are uncertain at the time the estimates are made, including the creditworthiness of specific tenants, specific industry trends and conditions, and general economic trends and conditions. Tenant and deferred rent receivables deemed probable of collection are carried net of allowances for uncollectible accounts, with increases or decreases in the allowances recorded through rental income on our consolidated statements of operations. Prior to the adoption of Topic 842 on January 1, 2019, the allowances were increased or decreased through provision for bad debts on our consolidated statements of operations. Current tenant receivables consist primarily of amounts due for contractual lease payments and reimbursements of common area maintenance expenses, property taxes, and other costs recoverable from tenants. With respect to the allowance for uncollectible tenant receivables, the specific identification methodology analysis relies on factors such as the age and nature of the receivables, the payment history and financial condition of the tenant, our assessment of the tenant’s ability to meet its lease obligations, and the status of negotiations of any disputes with the tenant. Deferred rent receivables represent the amount by which the cumulative straight-line rental revenue recorded to date exceeds cash rents billed to date under the lease agreement. With respect to the allowance for deferred rent receivables, given the longer-term nature of these receivables, the specific identification methodology analysis evaluates each of our significant tenants and any tenants on our internal watchlist and relies on factors such as each tenant’s financial condition and its ability to meet its lease obligations. We evaluate our reserve levels quarterly based on changes in the financial condition of tenants and our assessment of the tenant’s ability to meet its lease obligations, overall economic conditions, and the current business environment. Acquisitions Acquisitions of operating properties and development and redevelopment opportunities generally do not meet the definition of a business and are accounted for as asset acquisitions, as substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or a group of similar identifiable assets. For these asset acquisitions, we record the acquired tangible and intangible assets and assumed liabilities based on each asset’s and liability’s relative fair value at the acquisition date of the total purchase price plus any capitalized acquisition costs. We record the acquired tangible and intangible assets and assumed liabilities of acquisitions of operating properties and development and redevelopment opportunities that meet the accounting criteria to be accounted for as business combinations at fair value at the acquisition date. Transaction costs associated with asset acquisitions, including costs incurred during negotiation, are capitalized in addition to the purchase price of the acquisition. The acquired assets and assumed liabilities for an acquisition generally include but are not limited to (i) land and improvements, buildings and improvements, undeveloped land and construction in progress and (ii) identified tangible and intangible assets and liabilities associated with in-place leases, including tenant improvements, leasing costs, value of above-market and below-market operating leases and ground leases, acquired in-place lease values and tenant relationships, if any. Any debt assumed and equity (including common units of the Operating Partnership) issued in connection with a property acquisition is recorded at fair value on the date of acquisition. The fair value of land and improvements is derived from comparable sales of land and improvements within the same submarket and/or region. The fair value of buildings and improvements, tenant improvements and leasing costs considers the value of the property as if it was vacant as well as current replacement costs and other relevant market rate information. The fair value of the above-market or below-market component of an acquired in-place operating lease is based upon the present value (calculated using a market discount rate) of the difference between (i) the contractual rents to be paid pursuant to the lease over its remaining non-cancellable lease term and (ii) our estimate of the rents that would be paid using fair market rental rates and rent escalations at the date of acquisition measured over the remaining non-cancellable term of the lease for above-market operating leases and the initial non-cancellable term plus the term of any below-market fixed rate renewal options, if applicable, for below-market operating leases. Our below-market operating leases generally do not include fixed rate or below-market renewal options. The amounts recorded for above-market operating leases are included in deferred leasing costs and acquisition-related intangible assets, net on the balance sheet and are amortized on a straight-line basis as a reduction of rental income over the remaining term of the applicable leases. The amounts recorded for below-market operating leases are included in deferred revenue and acquisition-related intangible liabilities, net on the balance sheet and are amortized on a straight-line basis as an increase to rental income over the remaining term of the applicable leases plus the term of any below-market fixed rate renewal options, if applicable. The amortization of a below-market ground lease obligation is recorded as an increase to ground lease expense in the consolidated statements of operations for the periods presented. The amortization of an above-market ground lease obligation is recorded as a decrease to ground lease expense in the consolidated statements of operations for the periods presented. The fair value of acquired in-place leases is derived based on our assessment of lost revenue and costs incurred for the period required to lease the “assumed vacant” property to the occupancy level when purchased. The amount recorded for acquired in-place leases is included in deferred leasing costs and acquisition-related intangible assets, net on the balance sheet and amortized as an increase to depreciation and amortization expense over the remaining term of the applicable leases. Fully amortized intangible assets are written off each quarter. Operating Properties Operating properties are generally carried at historical cost less accumulated depreciation. Properties held for sale are reported at the lower of the carrying value or the fair value less estimated cost to sell. The cost of operating properties includes the purchase price or development costs of the properties. Costs incurred for the renovation and betterment of the operating properties are capitalized to our investment in that property. Maintenance and repairs are charged to expense as incurred. When evaluating properties to be held and used for potential impairment, we first evaluate whether there are any indicators of impairment for any of our properties. If any impairment indicators are present for a specific property, we then evaluate the regional market conditions that could reasonably affect the property. If there are negative changes and trends in that regional market, we then perform an undiscounted cash flow analysis and compare the net carrying amount of the property to the property’s estimated undiscounted future cash flow over the anticipated holding period. If the estimated undiscounted future cash flow is less than the net carrying amount of the property, we perform an impairment loss calculation to determine if the fair value of the property is less than the net carrying value of the property. Our impairment loss calculation compares the net carrying amount of the property to the property’s estimated fair value, which may be based on estimated discounted future cash flow calculations or third-party valuations or appraisals. We would recognize an impairment loss if the property's net carrying amount exceeds the property's estimated fair value. If we were to recognize an impairment loss, the estimated fair value of the property becomes its new cost basis. For a depreciable long-lived asset, the new cost basis would be depreciated (amortized) over the remaining useful life of that asset. Cost Capitalization All costs clearly associated with the development, redevelopment and construction of a property are capitalized as project costs, including internal compensation costs. In addition, the following costs are capitalized as project costs during periods in which activities necessary to prepare development and redevelopment properties for their intended use are in progress: pre-construction costs essential to the development of the property, interest, real estate taxes and insurance. • For office, life science and retail development and redevelopment properties that are pre-leased, we cease capitalization when revenue recognition commences, which is upon substantial completion of tenant improvements deemed to be the Company’s asset for accounting purposes. • For office, life science and retail development and redevelopment properties that are not pre-leased, we may not immediately build out the tenant improvements. Therefore, we cease capitalization when revenue recognition commences upon substantial completion of the tenant improvements deemed to be the Company's asset for accounting purposes, but in any event, no later than one year after the cessation of major construction activities. We also cease capitalization on a development or redevelopment property when activities necessary to prepare the property for its intended use have been suspended. • For office, life science and retail development or redevelopment properties with multiple tenants and phased leasing, we cease capitalization and begin depreciation on the portion of the development or redevelopment property for which revenue recognition has commenced. • For residential development properties, we cease capitalization when the property is substantially complete and available for occupancy. Once major base building construction activities have ceased and the development or redevelopment property or phases of the development or redevelopment project is placed in service, which may occur in phases or for an entire building or project, the costs capitalized to construction in progress are transferred to land and improvements, buildings and improvements, and deferred leasing costs on our consolidated balance sheets as the historical cost of the property. Depreciation and Amortization of Buildings and Improvements The costs of buildings and improvements and tenant improvements are depreciated using the straight-line method of accounting over the estimated useful lives set forth in the table below. Depreciation expense for buildings and improvements for the three years ended December 31, 2020, 2019, and 2018 was $244.8 million, $211.9 million, and $198.6 million, respectively. Asset Description Depreciable Lives Buildings and improvements 25 – 40 years Tenant improvements 1 – 20 years (1) ____________________ (1) Tenant improvements are amortized over the shorter of the lease term or the estimated useful life. Real Estate Assets Held for Sale, Dispositions and Discontinued Operations A real estate asset is classified as held for sale when certain criteria are met, including but not limited to the availability of the asset for immediate sale, the existence of an active program to locate a buyer and the probable sale or transfer of the asset within one year. If such criteria are met, we present the applicable assets and liabilities related to the real estate asset, if material, separately on the balance sheet as held for sale and we would cease to record depreciation and amortization expense. Real estate assets held for sale are reported at the lower of their carrying value or their estimated fair value less the estimated costs to sell. As of December 31, 2020 and 2019, we did not have any properties classified as held for sale. Property disposals representing a strategic shift that have (or will have) a major effect on the Company’s operations and financial results, such as a major line of business, a major geographical area or a major equity investment, are required to be presented as discontinued operations. If we were to determine that a property disposition represents a strategic shift, the revenues, expenses and net gain (loss) on dispositions of the property would be recorded in discontinued operations for all periods presented through the date of the applicable disposition. The operations of the properties sold during the years ended December 31, 2020, 2019 and 2018 are presented in continuing operations as they did not represent a strategic shift in the Company’s operations and financial results. The net gains (losses) on dispositions of non-depreciable real estate property, including land, are reported in the consolidated statements of operations as gains (losses) on sale of land within continuing operations in the period the land is sold. The net gains (losses) on dispositions of depreciable real estate property are reported in the consolidated statements of operations as gains on sales of depreciable operating properties within continuing operations in the period the property is sold. Cash and Cash Equivalents We consider all highly-liquid investments with original maturities of three months or less to be cash equivalents. Restricted Cash Restricted cash consists of cash proceeds from dispositions that are temporarily held at qualified intermediaries for purposes of facilitating potential Section 1031 Exchanges and cash held in escrow related to acquisition and disposition holdbacks. Restricted cash also includes cash held as collateral to provide credit enhancement for the Operating Partnership’s mortgage debt, including cash reserves for capital expenditures, tenant improvements and property taxes. As of December 31, 2020, we had $74.9 million of restricted cash held at qualified intermediaries for the purpose of facilitating Section 1031 Exchanges. In January 2021, the Section 1031 Exchange was terminated and the cash proceeds were released from the qualified intermediary. We did not have any restricted cash held at qualified intermediaries for the purpose of facilitating Section 1031 Exchanges at December 31, 2019. Marketable Securities / Deferred Compensation Plan Marketable securities reported in our consolidated balance sheets represent the assets held in connection with the Kilroy Realty Corporation 2007 Deferred Compensation Plan (the “Deferred Compensation Plan”) (see Note 16 “Employee Benefit Plans” for additional information). The Deferred Compensation Plan assets are held in a limited rabbi trust and invested in various mutual and money market funds. As a result, the marketable securities are treated as trading securities for financial reporting purposes and are adjusted to fair value at the end of each accounting period, with the corresponding gains and losses recorded in interest income and other net investment gains (losses). At the time eligible management employees (“Participants”) defer compensation or earn mandatory Company contributions, or if we were to make a discretionary contribution, we record compensation cost and a corresponding deferred compensation plan liability, which is included in accounts payable, accrued expenses, and other liabilities on our consolidated balance sheets. This liability is adjusted to fair value at the end of each accounting period based on the performance of the benchmark funds selected by each Participant, and the impact of adjusting the liability to fair value is recorded as an increase or decrease to compensation cost. The impact of adjusting the deferred compensation plan liability to fair value and the changes in the value of the marketable securities held in connection with the Deferred Compensation Plan generally offset and therefore do

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2020
Asset Acquisitions [Abstract]
Acquisitions	Acquisitions Operating Property Acquisitions We did not acquire any operating properties during the year ended December 31, 2020. During the year ended December 31, 2019, we acquired the 19-building creative office campus listed below in one transaction from an unrelated third party. Property Date of Acquisition Number of Buildings Rentable Square Feet (unaudited) Purchase Price (in millions) (1) 2019 Acquisitions 3101-3243 La Cienega Boulevard, Culver City, CA (2) October 15, 2019 19 151,908 $ 186.0 ________________________ (1) Excludes acquisition-related costs. (2) The results of operations for the properties acquired during 2019 contributed $3.7 million to revenue and a net loss of $0.1 million for the year ended December 31, 2019 primarily due to a write-off of lease-related intangible assets as a result of an early lease termination during the year ended December 31, 2019. The related assets, liabilities and results of operations of the acquired properties are included in the consolidated financial statements as of the date of acquisition. The following table summarizes the estimated relative fair values of the assets and liabilities assumed at the acquisition date for our 2019 operating property acquisitions: Total 2019 Operating Property Acquisition (1) Assets Land and improvements $ 150,561 Buildings and improvements (2) 30,932 Deferred leasing costs and acquisition-related intangible assets (3) 12,063 Right of use ground lease asset (4) 13,334 Total assets acquired $ 206,890 Liabilities Acquisition-related intangible liabilities (5) $ 9,950 Ground lease liability (4) 10,940 Total liabilities assumed $ 20,890 Net assets and liabilities acquired $ 186,000 ________________________ (1) The purchase price of the acquisition completed during the year ended December 31, 2019 was less than 10% of the Company’s total assets as of December 31, 2018. (2) Represents buildings, building improvements and tenant improvements. (3) Represents in-place leases (approximately $9.2 million with a weighted average amortization period of 3.3 years) and leasing commissions (approximately $2.9 million with a weighted average amortization period of 3.5 years). (4) We evaluated the ground lease assumed in connection with the 2019 operating property acquisition and concluded it met the criteria to be classified as an operating lease. The discount rate used in determining the present value of the minimum future lease payments was 4.79%. The right of use asset ground lease asset is equal to the ground lease liability adjusted for above and below market intangibles and deferred leasing costs. Refer to Note 18 “Commitments and Contingencies” for further discussion of the Company's ground lease obligations. (5) Represents below-market leases (approximately $10.0 million with a weighted average amortization period of 3.5 years). Development Project Acquisitions We did not acquire any development sites during the year ended December 31, 2020. During the year ended December 31, 2019, we acquired the following development sites in two transactions from unrelated third parties. The acquisitions were funded from various sources of liquidity including proceeds from the Company’s unsecured revolving credit facility, the issuance of debt and the settlement of the Company’s 2018 forward equity sale agreements. Project Date of Acquisition City/Submarket Purchase Price (in millions) 2019 Acquisitions 1335 Broadway & 901 Park Boulevard, San Diego, CA (1) August 19, 2019 East Village $ 40.0 Seattle CBD Project (2) December 12, 2019 Seattle CBD 133.0 Total 2019 Acquisitions $ 173.0 _______________________ (1) Excludes acquisition-related costs. In connection with this acquisition, we also recorded $4.0 million in accrued liabilities and environmental remediation liabilities at the date of acquisition, which are not included in the purchase price above. As of December 31, 2019, the purchase price and our current estimate of assumed liabilities are included in undeveloped land and construction in progress and the assumed liabilities are included in accounts payable, accrued expenses and other liabilities on the Company’s consolidated balance sheets. (2) Excludes acquisition-related costs. In connection with this acquisition, we also recorded $6.3 million in accrued liabilities and environmental remediation liabilities at the date of acquisition, which are not included in the purchase price above. As of December 31, 2019, the purchase price and our current estimate of assumed liabilities are included in undeveloped land and construction in progress and the assumed liabilities are included in accounts payable, accrued expenses and other liabilities on the Company’s consolidated balance sheets. In addition, as of December 31, 2020 and 2019, the Company had $10.0 million in restricted cash, which is excluded from the purchase price above, related to this acquisition which may be payable to the seller only if certain events occur within three years following the date of acquisition. In addition to the acquisitions listed above, during 2019, we acquired an additional land parcel for an existing development project for $99.5 million. Acquisition Costs

Dispositions

Dispositions	12 Months Ended
	Dec. 31, 2020
Discontinued Operations and Disposal Groups [Abstract]
Dispositions	Dispositions Operating Property Dispositions The following table summarizes the operating properties sold during the years ended December 31, 2020, 2019 and 2018: Location Month of Disposition Number of Buildings Rentable Sales Price (in millions) (1) 2020 Dispositions 331 Fairchild Drive, Mountain View, CA December 1 87,147 $ 75.9 Total 2020 Dispositions 1 87,147 $ 75.9 2019 Dispositions 2829 Townsgate Road, Thousand Oaks, CA May 1 84,098 $ 18.3 2211 Michelson Drive, Irvine, CA October 1 271,556 115.5 Total 2019 Dispositions 2 355,654 $ 133.8 2018 Dispositions 1310-1327 Chesapeake Terrace, Sunnyvale, CA November 4 266,982 $ 160.3 Plaza Yarrow Bay Properties (2) November 4 279,924 134.5 23925, 23975, & 24025 Park Sorrento, Calabasas, CA December 3 225,340 78.2 Total 2018 Dispositions 11 772,246 $ 373.0 ____________________ (1) Represents gross sales price before broker commissions and closing costs. (2) The Plaza Yarrow Bay Properties include the following properties: 10210, 10220 and 10230 NE Points Drive & 3933 Lake Washington Boulevard NE in Kirkland, Washington. The total gains on the sales of the operating properties sold during the years ended December 31, 2020, 2019 and 2018 were $35.5 million, $36.8 million and $142.9 million, respectively. Land Dispositions We did not dispose of any land parcels during the years ended December 31, 2020 and 2019. During the year ended December 31, 2018, in connection with the Plaza Yarrow Bay Properties disposition listed above, we recognized a gain on sale of land of $11.8 million. Restricted Cash Related to Dispositions As of December 31, 2020, approximately $74.9 million of net proceeds related to the operating property disposition during the year ended December 31, 2020 were temporarily being held at a qualified intermediary at our direction, for the purpose of facilitating a Section 1031 Exchange. The cash proceeds were included in restricted cash on our consolidated balance sheets at December 31, 2020. During January 2021, the Section 1031 Exchange was terminated and the cash proceeds were released from the qualified intermediary. We did not have any restricted cash related to dispositions or Section 1031 Exchanges as of December 31, 2019.

Deferred Leasing Costs and Acqu

Deferred Leasing Costs and Acquisition-Related Intangible Assets and Liabilities, net	12 Months Ended
	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Deferred Leasing Costs and Acquisition-Related Intangible Assets and Liabilities, net	Deferred Leasing Costs and Acquisition-Related Intangible Assets and Liabilities, net The following table summarizes our deferred leasing costs and acquisition-related intangible assets (acquired value of leasing costs, above-market operating leases, and in-place leases) and intangible liabilities (acquired value of below-market operating leases) as of December 31, 2020 and 2019: December 31, 2020 December 31, 2019 (in thousands) Deferred Leasing Costs and Acquisition-related Intangible Assets, net: Deferred leasing costs $ 300,556 $ 286,026 Accumulated amortization (104,277) (100,145) Deferred leasing costs, net 196,279 185,881 Above-market operating leases — 611 Accumulated amortization — (116) Above-market operating leases, net — 495 In-place leases 40,323 58,076 Accumulated amortization (25,653) (31,647) In-place leases, net 14,670 26,429 Total deferred leasing costs and acquisition-related intangible assets, net $ 210,949 $ 212,805 Acquisition-related Intangible Liabilities, net: (1) Below-market operating leases $ 26,405 $ 51,263 Accumulated amortization (13,060) (27,171) Below-market operating leases, net 13,345 24,092 Total acquisition-related intangible liabilities, net $ 13,345 $ 24,092 ____________________ (1) Included in deferred revenue and acquisition-related intangible liabilities, net in the consolidated balance sheets. The following table sets forth amortization related to deferred leasing costs and acquisition-related intangibles for the years ended December 31, 2020, 2019 and 2018. Year Ended December 31, 2020 2019 2018 (in thousands) Deferred leasing costs (1) $ 33,624 $ 35,779 $ 34,341 Above-market operating leases (2) 495 192 444 In-place leases (1) 11,759 18,615 15,915 Below-market ground lease obligation (3) — — 8 Below-market operating leases (4) (10,748) (9,398) (10,192) Above-market ground lease obligation (3) — — (101) Total $ 35,130 $ 45,188 $ 40,415 ____________________ (1) The amortization of deferred leasing costs and in-place leases is recorded to depreciation and amortization expense and the amortization of lease incentives is recorded as a reduction to rental income in the consolidated statements of operations for the periods presented. (2) The amortization of above-market operating leases is recorded as a decrease to rental income in the consolidated statements of operations for the periods presented. (3) Upon adoption of Topic 842 on January 1, 2019 (refer to Note 2 “Basis of Presentation and Significant Accounting Policies”), we no longer separately recognize above or below-market ground lease obligations. Refer to Note 18 “Commitments and Contingencies” for further discussion of our ground lease obligations. (4) The amortization of below-market operating leases is recorded as an increase to rental income in the consolidated statements of operations for the periods presented. The following table sets forth the estimated annual amortization expense related to deferred leasing costs and acquisition-related intangibles as of December 31, 2020 for future periods: Year Deferred Leasing Costs In-Place Leases Below-Market Operating Leases (1) (in thousands) 2021 $ 31,048 $ 6,531 $ (4,152) 2022 28,334 3,885 (3,167) 2023 24,470 1,534 (1,486) 2024 21,545 584 (812) 2025 19,726 473 (710) Thereafter 71,156 1,663 (3,018) Total $ 196,279 $ 14,670 $ (13,345) ____________________ (1) Represents estimated annual amortization related to below-market operating leases. Amounts will be recorded as an increase to rental income in the consolidated statements of operations.

Receivables

Receivables	12 Months Ended
	Dec. 31, 2020
Receivables [Abstract]
Receivables	Receivables Current Receivables, net Current receivables, net is primarily comprised of contractual rents and other lease-related obligations due from tenants. The balance consisted of the following as of December 31, 2020 and 2019: December 31, 2020 December 31, 2019 (in thousands) Current receivables $ 13,806 $ 27,660 Allowance for uncollectible tenant receivables (1) (1,799) (1,171) Current receivables, net $ 12,007 $ 26,489 ____________________ (1) Refer to Note 2 “Basis of Presentation and Significant Accounting Policies” for discussion of our accounting policies related to the allowance for uncollectible tenant receivables for additional information regarding changes in our allowance for uncollectible tenant receivables. Deferred Rent Receivables, net Deferred rent receivables, net consisted of the following as of December 31, 2020 and 2019: December 31, 2020 December 31, 2019 (in thousands) Deferred rent receivables $ 387,462 $ 339,489 Allowance for deferred rent receivables (1) (804) (1,552) Deferred rent receivables, net $ 386,658 $ 337,937 ____________________

Prepaid Expenses and Other Asse

Prepaid Expenses and Other Assets, Net	12 Months Ended
	Dec. 31, 2020
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid Expenses and Other Assets, Net	Prepaid Expenses and Other Assets, Net Prepaid expenses and other assets, net consisted of the following at December 31, 2020 and 2019: December 31, 2020 December 31, 2019 (in thousands) Furniture, fixtures and other long-lived assets, net $ 43,367 $ 35,286 Prepaid expenses 10,193 18,724 Notes receivable, net (1) — 1,651 Total prepaid expenses and other assets, net $ 53,560 $ 55,661 ____________________ (1) During the year ended December 31, 2020, the balance of the note receivable was written-off and the note receivable was placed on non-accrual status. We do not recognize interest income on non-accrual financing receivables. As of December 31, 2019, the note receivable was shown net of a valuation allowance of approximately $3.6 million.

Secured and Unsecured Debt of t

Secured and Unsecured Debt of the Company	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Secured and Unsecured Debt of the Company	Secured and Unsecured Debt of the Company In this Note 8, the “Company” refers solely to Kilroy Realty Corporation and not to any of our subsidiaries. The Company itself does not hold any indebtedness. All of our secured and unsecured debt is held directly by the Operating Partnership. The Company generally guarantees all the Operating Partnership’s unsecured debt obligations including the unsecured revolving credit facility, the unsecured term loan facility and all of the unsecured senior notes. At December 31, 2020 and 2019, the Operating Partnership had $3.7 billion and $3.3 billion, respectively, outstanding in total, including unamortized discounts and deferred financing costs, under these unsecured debt obligations. In addition, although the remaining $0.3 billion of the Operating Partnership’s debt as of December 31, 2020 and 2019, is secured and non-recourse to the Company, the Company provides limited customary secured debt guarantees for items such as voluntary bankruptcy, fraud, misapplication of payments and environmental liabilities. Debt Covenants and Restrictions

Secured and Unsecured Debt of_2

Secured and Unsecured Debt of the Operating Partnership	12 Months Ended
	Dec. 31, 2020
Debt Instrument [Line Items]
Secured and Unsecured Debt of the Operating Partnership	Secured and Unsecured Debt of the Company In this Note 8, the “Company” refers solely to Kilroy Realty Corporation and not to any of our subsidiaries. The Company itself does not hold any indebtedness. All of our secured and unsecured debt is held directly by the Operating Partnership. The Company generally guarantees all the Operating Partnership’s unsecured debt obligations including the unsecured revolving credit facility, the unsecured term loan facility and all of the unsecured senior notes. At December 31, 2020 and 2019, the Operating Partnership had $3.7 billion and $3.3 billion, respectively, outstanding in total, including unamortized discounts and deferred financing costs, under these unsecured debt obligations. In addition, although the remaining $0.3 billion of the Operating Partnership’s debt as of December 31, 2020 and 2019, is secured and non-recourse to the Company, the Company provides limited customary secured debt guarantees for items such as voluntary bankruptcy, fraud, misapplication of payments and environmental liabilities. Debt Covenants and Restrictions
Kilroy Realty L.P. [Member]
Debt Instrument [Line Items]
Secured and Unsecured Debt of the Operating Partnership	Secured and Unsecured Debt of the Operating Partnership Secured Debt The following table sets forth the composition of our secured debt as of December 31, 2020 and 2019: Annual Stated Interest Rate (1) GAAP Effective Rate (1)(2) Maturity Date December 31, Type of Debt 2020 2019 (in thousands) Mortgage note payable 3.57% 3.57% December 2026 $ 166,776 $ 170,000 Mortgage note payable (3) 4.48% 4.48% July 2027 87,589 89,502 Total secured debt $ 254,365 $ 259,502 Unamortized Deferred Financing Costs (783) (909) Total secured debt, net $ 253,582 $ 258,593 ____________________ (1) All interest rates presented are fixed-rate interest rates. (2) Represents the effective interest rate including the amortization of initial issuance discounts/premiums excluding the amortization of deferred financing costs. (3) The secured debt and the related properties that secure this debt are held in a special purpose entity and the properties are not available to satisfy the debts and other obligations of the Company or the Operating Partnership. The Operating Partnership’s secured debt was collateralized by operating properties with a combined net book value of approximately $222.0 million as of December 31, 2020. Although our mortgage loans are secured and non-recourse to the Company and the Operating Partnership, the Company provides limited customary secured debt guarantees for items such as voluntary bankruptcy, fraud, misapplication of payments and environmental liabilities. As of December 31, 2020, all of the Operating Partnership’s secured loans contained restrictions that would require the payment of prepayment penalties for the acceleration of outstanding debt. The mortgage notes payable are secured by deeds of trust on certain of our properties and the assignment of certain rents and leases associated with those properties. Unsecured Senior Notes - Registered Offerings In August 2020, the Operating Partnership issued $425.0 million aggregate principal amount of green unsecured senior notes in a registered public offering. The outstanding balance of the unsecured senior notes is included in unsecured debt, net of an initial issuance discount of $2.7 million, on our consolidated balance sheets. The unsecured senior notes, which are scheduled to mature on November 15, 2032, require semi-annual interest payments each May and November based on a stated annual interest rate of 2.500%. The Operating Partnership may redeem the notes at any time prior to August 15, 2032, either in whole or in part, subject to the payment of an early redemption premium prior to a par call option period commencing three months prior to maturity. In September 2019, the Operating Partnership issued $500.0 million of aggregate principal amount of unsecured senior notes in a registered public offering. The outstanding balance of the unsecured senior notes is included in unsecured debt, net of an initial issuance discount of $0.6 million, on our consolidated balance sheets. The unsecured senior notes, which are scheduled to mature on February 15, 2030, require semi-annual interest payments each February and August based on a stated annual interest rate of 3.050%. The Operating Partnership may redeem the notes at any time prior to February 15, 2030, either in whole or in part, subject to the payment of an early redemption premium prior to a par call option period commencing three months prior to maturity. Unsecured Senior Notes - Private Placement In April 2020, the Operating Partnership entered into a Note Purchase Agreement in connection with the issuance and sale of $350.0 million principal amount of the Operating Partnership’s 4.270% Senior Notes due January 31, 2031 (the “Notes due 2031”), pursuant to a private placement. The Notes due 2031 mature on their due date, unless earlier redeemed or prepaid pursuant to the terms of the Note Purchase Agreement. Interest on the Notes is payable semi-annually in arrears on April 18 and October 18 of each year beginning October 18, 2020. Unsecured Senior Notes - Early Redemption In December 2018, at our option, we early redeemed the $250.0 million aggregate principal amount of our outstanding 6.625% unsecured senior notes that were scheduled to mature on June 1, 2020. In connection with our early redemption, we incurred a $12.6 million loss on early extinguishment of debt comprised of an $11.8 million premium paid to the note holders at the redemption date and a $0.8 million write-off of the unamortized discount and unamortized deferred financing costs. Unsecured Senior Notes The following table summarizes the balance and significant terms of the registered unsecured senior notes issued by the Operating Partnership and outstanding, including the issuances noted above, and including unamortized discounts of $8.3 million and $6.5 million and unamortized deferred financing costs of $21.6 million and $18.7 million as of December 31, 2020 and 2019, respectively: Net Carrying Amount Issuance date Maturity date Stated Effective interest rate (1) 2020 2019 (in thousands) 2.500% Unsecured Senior Notes (2) August 2020 November 2032 2.500% 2.560% $ 425,000 $ — Unamortized discount and deferred financing costs (6,332) — Net carrying amount $ 418,668 $ — 4.270% Unsecured Senior Notes (3) April 2020 January 2031 4.270% 4.270% $ 350,000 $ — Unamortized discount and deferred financing costs (1,825) — Net carrying amount $ 348,175 $ — 3.050% Unsecured Senior Notes (4) September 2019 February 2030 3.050% 3.064% $ 500,000 $ 500,000 Unamortized discount and deferred financing costs (5,399) (5,998) Net carrying amount $ 494,601 $ 494,002 4.750% Unsecured Senior Notes (5) November 2018 December 2028 4.750% 4.800% $ 400,000 $ 400,000 Unamortized discount and deferred financing costs (3,952) (4,446) Net carrying amount $ 396,048 $ 395,554 4.350% Unsecured Senior Notes (6) October 2018 October 2026 4.350% 4.350% $ 200,000 $ 200,000 Unamortized discount and deferred financing costs (1,012) (1,186) Net carrying amount $ 198,988 $ 198,814 4.300% Unsecured Senior Notes (6) July 2018 July 2026 4.300% 4.300% $ 50,000 $ 50,000 Unamortized discount and deferred financing costs (246) (290) Net carrying amount $ 49,754 $ 49,710 3.450% Unsecured Senior Notes (7) December 2017 December 2024 3.450% 3.470% $ 425,000 $ 425,000 Unamortized discount and deferred financing costs (2,321) (2,907) Net carrying amount $ 422,679 $ 422,093 3.450% Unsecured Senior Notes (8) February 2017 February 2029 3.450% 3.450% $ 75,000 $ 75,000 Unamortized discount and deferred financing costs (347) (390) Net carrying amount $ 74,653 $ 74,610 3.350% Unsecured Senior Notes (8) February 2017 February 2027 3.350% 3.350% $ 175,000 $ 175,000 Unamortized discount and deferred financing costs (709) (825) Net carrying amount $ 174,291 $ 174,175 4.375% Unsecured Senior Notes (9) September 2015 October 2025 4.375% 4.444% $ 400,000 $ 400,000 Unamortized discount and deferred financing costs (2,631) (3,185) Net carrying amount $ 397,369 $ 396,815 4.250% Unsecured Senior Notes (10) July 2014 August 2029 4.250% 4.350% $ 400,000 $ 400,000 Unamortized discount and deferred financing costs (4,567) (5,100) Net carrying amount $ 395,433 $ 394,900 3.800% Unsecured Senior Notes (11) January 2013 January 2023 3.800% 3.800% $ 300,000 $ 300,000 Unamortized discount and deferred financing costs (560) (834) Net carrying amount $ 299,440 $ 299,166 Total Unsecured Senior Notes, Net $ 3,670,099 $ 2,899,839 ____________________ (1) Represents the effective interest rate including the amortization of initial issuance discounts, excluding the amortization of deferred financing costs. (2) Interest on these notes is payable semi-annually in arrears on May 15 and November 15 of each year. (3) Interest on these notes is payable semi-annually in arrears on April 18 and October 18 of each year. (4) Interest on these notes is payable semi-annually in arrears on February 15th and August 15th of each year. (5) Interest on these notes is payable semi-annually in arrears on June 15th and December 15th of each year. (6) Interest on these notes is payable semi-annually in arrears on April 18th and October 18th of each year. (7) Interest on these notes is payable semi-annually in arrears on June 15th and December 15th of each year. (8) Interest on these notes is payable semi-annually in arrears on February 17th and August 17th of each year. (9) Interest on these notes is payable semi-annually in arrears on April 1st and October 1st of each year. (10) Interest on these notes is payable semi-annually in arrears on February 15th and August 15th of each year. (11) Interest on these notes is payable semi-annually in arrears on January 15th and July 15th of each year. Unsecured Revolving Credit Facility and Term Loan Facility The following table summarizes the balance and terms of our unsecured revolving credit facility as of December 31, 2020 and 2019: December 31, 2020 December 31, 2019 (in thousands) Outstanding borrowings $ — $ 245,000 Remaining borrowing capacity 750,000 505,000 Total borrowing capacity (1) $ 750,000 $ 750,000 Interest rate (2) 1.14 % 2.76 % Facility fee-annual rate (3) 0.200% Maturity date July 2022 ____________________ (1) We may elect to borrow, subject to bank approval and obtaining commitments for any additional borrowing capacity, up to an additional $600.0 million under an accordion feature under the terms of the unsecured revolving credit facility and unsecured term loan facility. (2) Our unsecured revolving credit facility interest rate was calculated based on the contractual rate of LIBOR plus 1.000% as of December 31, 2020 and 2019. (3) Our facility fee is paid on a quarterly basis and is calculated based on the total borrowing capacity. In addition to the facility fee, we incurred debt origination and legal costs. As of December 31, 2020 and 2019, $2.1 million and $3.4 million of unamortized deferred financing costs, respectively, which are included in prepaid expenses and other assets, net on our consolidated balance sheets, remained to be amortized through the maturity date of our unsecured revolving credit facility. The Company intends to borrow under the unsecured revolving credit facility from time to time for general corporate purposes, to finance development and redevelopment expenditures, to fund potential acquisitions and to potentially repay long-term debt and to supplement cash balances given uncertainties and volatility in market conditions. In August 2020, the Company repaid in full the $150.0 million unsecured term loan facility. The following table summarizes the balance and terms of our unsecured term loan facility as of December 31, 2019, which is included in unsecured debt, net on our consolidated balance sheets: December 31, 2019 Outstanding borrowings $ 150,000 Remaining borrowing capacity — Total borrowing capacity (1) $ 150,000 Interest rate (2) 2.85 % Undrawn facility fee-annual rate 0.200% Maturity date July 2022 ____________________ (1) As of December 31, 2019, $0.7 million of unamortized deferred financing costs remained to be amortized through the maturity date of our unsecured term loan facility. (2) Our unsecured term loan facility interest rate was calculated based on the contractual rate of LIBOR plus 1.100% as of December 31, 2019. Debt Covenants and Restrictions The unsecured revolving credit facility, the unsecured senior notes, the Series A and B Notes due 2026, Series A and B Notes due 2027 and 2029, and Notes due 2031 and certain other secured debt arrangements contain covenants and restrictions requiring us to meet certain financial ratios and reporting requirements. Some of the more restrictive financial covenants include a maximum ratio of total debt to total asset value, a minimum fixed-charge coverage ratio, a minimum unsecured debt ratio and a minimum unencumbered asset pool debt service coverage ratio. Noncompliance with one or more of the covenants and restrictions could result in the full principal balance of the associated debt becoming immediately due and payable. We believe we were in compliance with all of our debt covenants as of December 31, 2020 and 2019. Debt Maturities The following table summarizes the stated debt maturities and scheduled amortization payments as of December 31, 2020: Year (in thousands) 2021 $ 5,342 2022 5,554 2023 305,775 2024 431,006 2025 406,246 Thereafter 2,800,442 Total aggregate principal value (1) $ 3,954,365 ________________________ (1) Includes gross principal balance of outstanding debt before the effect of the following at December 31, 2020: $22.4 million of unamortized deferred financing costs for the unsecured senior notes and secured debt and $8.3 million of unamortized discounts for the unsecured senior notes. Capitalized Interest and Loan Fees The following table sets forth gross interest expense, including debt discount/premium and deferred financing cost amortization, net of capitalized interest, for the years ended December 31, 2020, 2019 and 2018. The interest expense capitalized was recorded as a cost of development and increased the carrying value of undeveloped land and construction in progress. Year Ended December 31, 2020 2019 2018 (in thousands) Gross interest expense $ 150,325 $ 129,778 $ 117,789 Capitalized interest and deferred financing costs (79,553) (81,241) (68,068) Interest expense $ 70,772 $ 48,537 $ 49,721

Deferred Revenue and Acquisitio

Deferred Revenue and Acquisition-Related Intangible Liabilities, net	12 Months Ended
	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Deferred Revenue and Acquisition-Related Intangible Liabilities, net	Deferred Revenue and Acquisition-Related Intangible Liabilities, net Deferred revenue and acquisition-related intangible liabilities, net consisted of the following at December 31, 2020 and 2019: December 31, 2020 2019 (in thousands) Deferred revenue related to tenant-funded tenant improvements $ 88,645 $ 96,271 Other deferred revenue 26,533 19,125 Acquisition-related intangible liabilities, net (1) 13,345 24,092 Total $ 128,523 $139,488 _____________________ (1) See Note 5 “Deferred Leasing Costs and Acquisition-Related Intangible Assets and Liabilities, net” for additional information regarding our acquisition-related intangible liabilities. Deferred Revenue Related to Tenant-funded Tenant Improvements During the years ended December 31, 2020, 2019, and 2018, $22.5 million, $19.2 million and $18.4 million, respectively, of deferred revenue related to tenant-funded tenant improvements was amortized and recognized as rental income. The following is the estimated amortization of deferred revenue related to tenant-funded tenant improvements as of December 31, 2020 for the next five years and thereafter: Year Ending (in thousands) 2021 $ 16,216 2022 15,188 2023 13,367 2024 11,325 2025 8,564 Thereafter 23,985 Total $ 88,645

Noncontrolling Interests on the

Noncontrolling Interests on the Company’s Consolidated Financial Statements	12 Months Ended
	Dec. 31, 2020
Noncontrolling Interest [Abstract]
Noncontrolling Interests on the Company’s Consolidated Financial Statements	Noncontrolling Interests on the Company’s Consolidated Financial Statements Common Units of the Operating Partnership The Company owned a 99.0% and 98.1% common general partnership interest in the Operating Partnership as of December 31, 2020 and 2019, respectively. The remaining 1.0% and 1.9% common limited partnership interest as of December 31, 2020 and 2019, respectively, was owned by non-affiliated investors and certain of our executive officers and directors in the form of noncontrolling common units. There were 1,150,574 and 2,023,287 common units outstanding held by these investors, executive officers and directors as of December 31, 2020 and 2019, respectively. The decrease in the common units from December 31, 2019 to December 31, 2020 was attributable to 872,713 common unit redemptions. The noncontrolling common units may be redeemed by unitholders for cash. Except under certain circumstances, we, at our option, may satisfy the cash redemption obligation with shares of the Company’s common stock on a one-for-one basis. If satisfied in cash, the value for each noncontrolling common unit upon redemption is the amount equal to the average of the closing quoted price per share of the Company’s common stock, par value $.01 per share, as reported on the NYSE for the ten trading days immediately preceding the applicable redemption date. The aggregate value upon redemption of the then-outstanding noncontrolling common units was $65.4 million and $167.7 million as of December 31, 2020 and 2019, respectively. This redemption value does not necessarily represent the amount that would be distributed with respect to each noncontrolling common unit in the event of our termination or liquidation. In the event of our termination or liquidation, it is expected in most cases that each common unit would be entitled to a liquidating distribution equal to the liquidating distribution payable in respect of each share of the Company’s common stock. Noncontrolling Interest in Consolidated Property Partnerships In August 2016, the Operating Partnership entered into agreements with Norges Bank Real Estate Management (“NBREM”) whereby NBREM made contributions, through two REIT subsidiaries, for a 44% common equity interest in two existing companies that owned the Company’s 100 First Street and 303 Second Street office properties located in San Francisco, California. The transactions did not meet the criteria to qualify as sales of real estate because the Company continues to effectively control the properties and therefore continued to account for the 100 First Street and 303 Second Street office properties on a consolidated basis in its financial statements. At formation, the Company accounted for the transactions as equity transactions and recognized noncontrolling interests in its consolidated balance sheets. The noncontrolling interests in 100 First LLC and 303 Second LLC as of December 31, 2020 and 2019 were $191.9 million and $189.6 million, respectively. The remaining amount of noncontrolling interests in consolidated property partnerships represents the third party equity interest in Redwood LLC. This noncontrolling interest was $5.6 million and $5.8 million as of December 31, 2020 and 2019, respectively. Consolidated Property Partnerships In August 2016, the Operating Partnership entered into agreements with NBREM whereby NBREM made contributions, through two REIT subsidiaries, for a 44% common equity interest in two existing companies that owned the Company’s 100 First Street and 303 Second Street office properties located in San Francisco, California. Refer to Note 11 for additional information regarding these consolidated property partnerships.

Noncontrolling Interests on t_2

Noncontrolling Interests on the Operating Partnership’s Consolidated Financial Statements	12 Months Ended
	Dec. 31, 2020
Noncontrolling Interest [Abstract]
Noncontrolling Interests on the Operating Partnership’s Consolidated Financial Statements	Noncontrolling Interests on the Company’s Consolidated Financial Statements Common Units of the Operating Partnership The Company owned a 99.0% and 98.1% common general partnership interest in the Operating Partnership as of December 31, 2020 and 2019, respectively. The remaining 1.0% and 1.9% common limited partnership interest as of December 31, 2020 and 2019, respectively, was owned by non-affiliated investors and certain of our executive officers and directors in the form of noncontrolling common units. There were 1,150,574 and 2,023,287 common units outstanding held by these investors, executive officers and directors as of December 31, 2020 and 2019, respectively. The decrease in the common units from December 31, 2019 to December 31, 2020 was attributable to 872,713 common unit redemptions. The noncontrolling common units may be redeemed by unitholders for cash. Except under certain circumstances, we, at our option, may satisfy the cash redemption obligation with shares of the Company’s common stock on a one-for-one basis. If satisfied in cash, the value for each noncontrolling common unit upon redemption is the amount equal to the average of the closing quoted price per share of the Company’s common stock, par value $.01 per share, as reported on the NYSE for the ten trading days immediately preceding the applicable redemption date. The aggregate value upon redemption of the then-outstanding noncontrolling common units was $65.4 million and $167.7 million as of December 31, 2020 and 2019, respectively. This redemption value does not necessarily represent the amount that would be distributed with respect to each noncontrolling common unit in the event of our termination or liquidation. In the event of our termination or liquidation, it is expected in most cases that each common unit would be entitled to a liquidating distribution equal to the liquidating distribution payable in respect of each share of the Company’s common stock. Noncontrolling Interest in Consolidated Property Partnerships In August 2016, the Operating Partnership entered into agreements with Norges Bank Real Estate Management (“NBREM”) whereby NBREM made contributions, through two REIT subsidiaries, for a 44% common equity interest in two existing companies that owned the Company’s 100 First Street and 303 Second Street office properties located in San Francisco, California. The transactions did not meet the criteria to qualify as sales of real estate because the Company continues to effectively control the properties and therefore continued to account for the 100 First Street and 303 Second Street office properties on a consolidated basis in its financial statements. At formation, the Company accounted for the transactions as equity transactions and recognized noncontrolling interests in its consolidated balance sheets. The noncontrolling interests in 100 First LLC and 303 Second LLC as of December 31, 2020 and 2019 were $191.9 million and $189.6 million, respectively. The remaining amount of noncontrolling interests in consolidated property partnerships represents the third party equity interest in Redwood LLC. This noncontrolling interest was $5.6 million and $5.8 million as of December 31, 2020 and 2019, respectively. Consolidated Property Partnerships In August 2016, the Operating Partnership entered into agreements with NBREM whereby NBREM made contributions, through two REIT subsidiaries, for a 44% common equity interest in two existing companies that owned the Company’s 100 First Street and 303 Second Street office properties located in San Francisco, California. Refer to Note 11 for additional information regarding these consolidated property partnerships.

Stockholders' Equity of the Com

Stockholders' Equity of the Company	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Stockholders' Equity of the Company	Stockholders’ Equity of the Company Common Stock Increase in Authorized Shares On May 19, 2020, the Company’s stockholders approved a proposal to amend and restate the Company’s charter to increase the number of authorized shares of common stock that the Company has the authority to issue from 150,000,000 shares to 280,000,000 shares. Forward Equity Offerings and Settlements On February 18, 2020, the Company entered into forward equity sale agreements with certain financial institutions acting as forward purchasers in connection with an offering of 5,750,000 shares of common stock at an initial gross offering price of $494.5 million, or $86.00 per share, before underwriting discounts, commissions and offering expenses. The forward purchasers borrowed and sold an aggregate of 5,750,000 shares of common stock in the offering. The Company did not receive any proceeds from the sale of its shares of common stock by the forward purchasers at the time of the offering. On March 25, 2020, the Company physically settled these forward equity sale agreements. Upon settlement, the Company issued 5,750,000 shares of common stock for net proceeds of $474.9 million and contributed the net proceeds to the Operating Partnership in exchange for an equal number of units in the Operating Partnership. In August 2018, the Company entered into forward equity sale agreements with certain financial institutions acting as forward purchasers in connection with an offering of 5,000,000 shares of common stock at an initial gross offering price of $360.5 million, or $72.10 per share, before underwriting discounts, commissions and offering expenses. The forward purchasers borrowed and sold an aggregate of 5,000,000 shares of common stock in the offering. The Company did not receive any proceeds from the sale of its shares of common stock by the forward purchasers at the time of the offering. In July 2019, the Company physically settled these forward equity sale agreements. Upon settlement, the Company issued 5,000,000 shares of common stock for net proceeds of $354.3 million and contributed the net proceeds to the Operating Partnership in exchange for an equal number of units in the Operating Partnership. At-The-Market Stock Offering Programs Under our at-the-market stock offering programs, which commenced in December 2014 and June 2018, we may offer and sell shares of our common stock from time to time in “at-the-market” offerings. During the year ended December 31, 2018, the Company completed its existing at-the-market stock offering program (the “2014 At-The-Market Program”) under which we sold an aggregate of $300.0 million in gross sales of shares. In June 2018, the Company commenced a new at-the-market stock offering program (the “2018 At-The-Market Program”) under which we may offer and sell shares of our common stock with an aggregate gross sales price of up to $500.0 million. In connection with the 2018 At-The-Market Program, the Company may also, at its discretion, enter into forward equity sale agreements. The use of forward equity sale agreements allows the Company to lock in a share price on the sale of shares of our common stock at the time an agreement is executed, but defer settling the forward equity sale agreements and receiving the proceeds from the sale of shares until a later date. During the year ended December 31, 2019, we executed various 12-month forward equity sale agreements under the 2018 Program with financial institutions acting as forward purchasers to sell 3,147,110 shares of common stock at a weighted average sales price of $80.08 per share before underwriting discounts, commissions and offering expenses. The Company did not receive any proceeds from the sale of its shares of common stock by forward purchasers at the time of sale. In March 2020, the Company physically settled all forward equity sale agreements entered into in 2019. Upon settlement, the Company issued 3,147,110 shares of common stock for net proceeds of $247.3 million and contributed the net proceeds to the Operating Partnership in exchange for an equal number of units in the Operating Partnership. We did not enter into any forward equity sale agreements under our at-the-market program during the year ended December 31, 2020. The following table sets forth information regarding settlements of forward equity sale agreements under our at-the-market offering program for the year ended December 31, 2020: Year Ended December 31, 2020 (in millions, except share and per share data) Shares of common stock settled during the period 3,147,110 Weighted average price per share of common stock $ 80.08 Aggregate gross proceeds $ 252.0 Aggregate net proceeds after selling commissions $ 247.3 Since commencement of the 2018 At-The-Market program through December 31, 2020, we have sold 3,594,576 shares of common stock under the 2018 At-The-Market Program. As of December 31, 2020, we may offer and sell shares of our common stock having an aggregate gross sales price up to approximately $214.2 million under the 2018 At-The-Market Program. The Company did not complete any direct sales of common stock under the program during the years ended December 31, 2020 and 2019. During the year ended December 31, 2018, we sold 447,466 shares of common stock under the 2018 At-The-Market Program and 1,369,729 shares of common stock under the 2014 At-The-Market Program. The following table sets forth information regarding direct sales of our common stock under our at-the-market offering programs for the year ended December 31, 2018: Year Ended December 31, 2018 (in millions, except share and per share data) Shares of common stock sold during the period 1,817,195 Weighted average price per share of common stock $ 73.64 Aggregate gross proceeds $ 133.8 Aggregate net proceeds after selling commissions $ 132.1 The proceeds from sales were used to fund development expenditures and general corporate purpose. Actual future sales will depend upon a variety of factors, including, but not limited to, market conditions, the trading price of the Company's common stock and our capital needs. We have no obligation to sell the remaining shares available for sale under the 2018 At-The-Market Program. Common Stock Repurchases As of December 31, 2020, 4,935,826 shares remained eligible for repurchase under a share repurchase program approved by the Company’s board of directors in 2016. The Company did not repurchase shares of common stock under this program during the three years ended December 31, 2020, 2019 and 2018. Accrued Dividends and Distributions The following tables summarize accrued dividends and distributions for the noted outstanding shares of common stock and noncontrolling units as of December 31, 2020 and 2019: December 31, 2020 2019 (in thousands) Dividends and Distributions payable to: Common stockholders $ 58,018 $ 51,418 Noncontrolling common unitholders of the Operating Partnership 575 981 RSU holders (1) 838 820 Total accrued dividends and distribution to common stockholders and noncontrolling unitholders $ 59,431 $ 53,219 _____________________ (1) The amount includes the value of the dividend equivalents that will be paid with additional RSUs (see Note 15 “Share-Based and Other Compensation” for additional information). December 31, 2020 2019 Outstanding Shares and Units: Common stock (1) 116,035,827 106,016,287 Noncontrolling common units 1,150,574 2,023,287 RSUs (2) 1,638,026 1,651,905 _____________________ (1) The amount includes nonvested shares. (2) The amount includes nonvested RSUs. Does not include 873,709 and 932,675 market measure-based RSUs because not all the necessary performance conditions have been met as of December 31, 2020 and 2019, respectively. Refer to Note 15 “Share-Based and Other Compensation” for additional information.

Partners' Capital of the Operat

Partners' Capital of the Operating Partnership	12 Months Ended
	Dec. 31, 2020
Partners' Capital [Abstract]
Partners' Capital of the Operating Partnership	Partners’ Capital of the Operating Partnership Common Units Issuance of Common Units In March 2020, the Company physically settled the forward equity sale agreements entered into in February 2020 (see Note 13 “Stockholders’ Equity of the Company”). Upon settlement, the Company issued 5,750,000 shares of common stock for net proceeds of $474.9 million and contributed the net proceeds to the Operating Partnership in exchange for 5,750,000 common units. In July 2019, the Company physically settled the forward equity sale agreements entered into in August 2018 (see Note 13 “Stockholders’ Equity of the Company”). Upon settlement, the Company issued 5,000,000 shares of common stock for net proceeds of $354.3 million and contributed the net proceeds to the Operating Partnership in exchange for 5,000,000 common units. At-The-Market Stock Offering Program In March 2020, the Company physically settled all forward equity sale agreements entered into in 2019. Upon settlement, the Company issued 3,147,110 shares of common stock for net proceeds of $247.3 million and contributed the net proceeds to the Operating Partnership in exchange for an equal number of units in the Operating Partnership. The Company did not issue any shares of common stock under its at-the-market programs and did not contribute any shares of common stock to the Operating Partnership during the year ended December 31, 2019. During the year ended December 31, 2018, the Company utilized its at-the-market stock offering programs to issue shares of common stock. See Note 13 “Stockholders’ Equity of the Company” for additional information. The net offering proceeds contributed by the Company to the Operating Partnership in exchange for common units for the year ended December 31, 2020 and 2018 are as follows: Year Ended December 31, 2020 2018 (in millions except share and per share data) Shares of common stock contributed by the Company 3,147,110 1,817,195 Common units exchanged for shares of common stock by the Company 3,147,110 1,817,195 Aggregate gross proceeds $ 252.0 $ 133.8 Aggregate net proceeds after selling commissions $ 247.3 $ 132.1 Common Units Outstanding The following table sets forth the number of common units held by the Company and the number of common units held by non-affiliated investors and certain of our executive officers and directors in the form of noncontrolling common units as well as the ownership interest held on each respective date: December 31, 2020 December 31, 2019 Company owned common units in the Operating Partnership 116,035,827 106,016,287 Company owned general partnership interest 99.0 % 98.1 % Noncontrolling common units of the Operating Partnership 1,150,574 2,023,287 Ownership interest of noncontrolling interest 1.0 % 1.9 % For a further discussion of the noncontrolling common units during the years ended December 31, 2020 and 2019, refer to Note 11 “Noncontrolling Interests on the Company’s Consolidated Financial Statements.” Accrued Distributions The following tables summarize accrued distributions for the noted common units as of December 31, 2020 and 2019: December 31, 2020 December 31, 2019 (in thousands) Distributions payable to: General partner $ 58,018 $ 51,418 Common limited partners 575 981 RSU holders (1) 838 820 Total accrued distributions to common unitholders $ 59,431 $ 53,219 _____________________ (1) The amount includes the value of the dividend equivalents that will be paid with additional RSUs (see Note 15 “Share-Based and Other Compensation” for additional information). December 31, 2020 December 31, 2019 Outstanding Units: Common units held by the general partner 116,035,827 106,016,287 Common units held by the limited partners 1,150,574 2,023,287 RSUs (1) 1,638,026 1,651,905 _____________________

Share-Based and Other Compensat

Share-Based and Other Compensation	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Share-Based and Other Compensation	Share-Based and Other Compensation Stockholder Approved Share-Based Incentive Compensation Plan As of December 31, 2020, we maintained one share-based incentive compensation plan, the Kilroy Realty 2006 Incentive Award Plan, as amended (the “2006 Plan”). The Company has a currently effective registration statement registering 10.7 million shares of our common stock for possible issuance under our 2006 Incentive Award Plan. As of December 31, 2020, approximately 1.5 million shares were available for grant under the 2006 Plan. The calculation of shares available for grant is presented after taking into account a reserve for a sufficient number of shares to cover the vesting and payment of 2006 Plan awards that were outstanding on that date, including performance-based vesting awards at (i) levels actually achieved for the performance conditions (as defined below) for which the performance period has been completed and (ii) at maximum levels for the other performance and market conditions (as defined below) for awards still in a performance period. The Executive Compensation Committee (the “Compensation Committee”) of the Company’s Board of Directors may grant the following share-based awards to eligible individuals, as provided under the 2006 Plan: incentive stock options, nonqualified stock options, restricted stock (nonvested shares), stock appreciation rights, performance shares, performance stock units, dividend equivalents, stock payments, deferred stock, restricted stock units (“RSUs”), profit interest units, performance bonus awards, performance-based awards and other incentive awards. For each award granted under our share-based incentive compensation programs, the Operating Partnership simultaneously issues to the Company a number of common units equal to the number of shares of common stock ultimately paid by the Company in respect of such awards. 2020, 2019 and 2018 Share-Based Compensation Grants In January 2020, the Executive Compensation Committee of the Company’s Board of Directors awarded 263,626 restricted stock units (“RSUs”) to certain officers of the Company under the 2006 Plan, which included 154,267 RSUs (at the target level of performance) that are subject to market and/or performance-based vesting requirements (the “2020 Performance-Based RSUs”) and 109,359 RSUs that are subject to time-based vesting requirements (the “2020 Time-Based RSUs”). During the year ended December 31, 2020, 5,148 2020 Time-Based RSUs, 12,263 2020 Performance-Based RSUs and 6,441 time-based and performance-based RSUs that were granted in prior years were forfeited. In February 2019, the Executive Compensation Committee of the Company’s Board of Directors awarded 288,378 RSUs to certain officers of the Company under the 2006 Plan, which included 143,396 RSUs (at the target level of performance) that are subject to market and/or performance-based vesting requirements (the “2019 Performance-Based RSUs”) and 144,982 RSUs that are subject to time-based vesting requirements (the “2019 Time-Based RSUs”). During the year ended December 31, 2019, 10,733 2019 Time-Based RSUs, 24,353 2019 Performance-Based RSUs and 98,844 time vest and performance RSUs that were granted in prior years were forfeited. In connection with entering into an amended employment agreement (the “Amended Employment Agreement”), on December 27, 2018, the Compensation Committee of the Company’s Board of Directors awarded John Kilroy, the Chairman of the Board of Directors and Chief Executive Officer of the Company and the Operating Partnership, 483,871 RSUs, providing an additional retention incentive during the term of the agreement and enticing Mr. Kilroy to delay his retirement. Of these RSUs awarded, 266,130 RSUs (at the target level of performance) are subject to market-based vesting requirements and 217,741 RSUs are subject to time-based vesting requirements. In addition to Mr. Kilroy’s award, the Compensation Committee of the Company’s Board of Directors awarded 161,290 RSUs to certain members of management. Of these RSUs awarded, 80,647 RSUs (at the target level of performance) are subject to market-based vesting requirements (together totaling 346,777 target RSUs with Mr. Kilroy’s award, the “December 2018 Market-Based RSUs”) and 80,643 RSUs are subject to time-based vesting requirements (together totaling 298,384 RSUs with Mr. Kilroy’s award, the “December 2018 Time-Based RSUs”). In January and February 2018, the Executive Compensation Committee of the Company’s Board of Directors awarded 282,038 RSUs to certain officers of the Company under the 2006 Plan, which included 158,205 RSUs (at the target level of performance) that are subject to market and/or performance-based vesting requirements (the “2018 Performance-Based RSUs”) and 123,833 RSUs that are subject to time-based vesting requirements (the “2018 Time-Based RSUs”). Additionally, during 2018, 14,999 RSUs were granted to the board of directors and certain members of management subject to time vesting requirements. December 2018 Market-Based RSU Grant Between 0% and 200% of the total 346,777 target number of December 2018 Market-Based RSUs will be eligible to vest based on the Company’s relative total shareholder return (“TSR”) versus a comparative group of companies that consist of companies in the SNL US REIT Office Index over the performance period. An initial number of RSUs (the “Initial Number of RSUs”) will be determined at the end of 2021 based on a three year performance period (consisting of calendar years 2019 through 2021). Once the Initial Number of RSUs is determined, 75% of the Initial Number of RSUs will be scheduled to vest on January 5, 2022. The remaining 25% of the Initial Number of RSUs will be scheduled to vest on January 5, 2023, subject to adjustment based on the Company’s relative TSR for the entire four-year performance period (2019 through 2022). The December 2018 Market-Based RSUs are also subject to service vesting requirements through the scheduled vest dates. Each December 2018 Market-Based RSU represents the right to receive one share of our common stock in the future, subject to, and as modified by, the Company’s level of achievement of the applicable market conditions. The December 27, 2018 grant date fair value of the December 2018 Market-Based RSUs was $23.8 million. The fair value was calculated using a Monte Carlo simulation pricing model based on the assumptions in the table below. For the years ended December 31, 2020, 2019 and 2018, we recorded compensation expense based upon the $68.66 grant date fair value per share. Compensation expense for the December 2018 Market-Based RSUs is recognized using a graded vesting approach, where 75% of the fair value will be recognized on a straight-line basis over the three-year initial performance period through the end of 2021, and the remaining 25% of the fair value will be recognized on a straight-line basis over the four-year final performance period through the end of 2022. The following table summarizes the assumptions utilized in the Monte Carlo simulation pricing models: December 2018 Market-Based RSU Award Fair Value Assumptions Valuation date December 27, 2018 Fair value per share on valuation date $68.66 Expected share price volatility 23.0% Risk-free interest rate 2.4% The computation of expected volatility was based on a blend of the historical volatility of our shares of common stock over a period of twice the performance period and implied volatility data based on the observed pricing of six month publicly-traded options on shares of our common stock. The risk-free interest rate was based on the yield curve on zero-coupon U.S. Treasury STRIP securities in effect at December 27, 2018. 2020, 2019 and 2018 Annual Performance-Based RSU Grants The 2020 Performance-Based RSUs are scheduled to vest at the end of a three year period (consisting of calendar years 2020-2022). A target number of 2020 Performance-Based RSUs were awarded, and the final number of 2020 Performance-Based RSUs that vest (which may be more or less than the target number) will be based upon (1) the achievement of pre-set FFO per share goals for the year ending December 31, 2020 that applies to 100% of the Performance-Based RSUs awarded (the “2020 FFO Performance Condition”) and (2) a performance measure that applies to 50% of the award based upon a measure of the Company’s average debt to EBITDA ratio for the three year performance period (the “2020 Debt to EBITDA Ratio Performance Condition”) and a market measure that applies to the other 50% of the award based upon the relative ranking of the Company’s total stockholder return for the three year performance period compared to the total stockholder returns of an established comparison group of companies over the same period (the “2020 Market Condition”). The 2020 Performance-Based RSUs are also subject to a three year service vesting provision (the “service vesting condition”) and are scheduled to cliff vest on the date the final vesting percentage is determined following the end of the three year performance period under the awards. The 2020 FFO Performance Condition was achieved at 100% of target for all participants. The number of 2020 Performance-Based RSUs ultimately earned could fluctuate from the target number of 2020 Performance-Based RSUs granted based upon the levels of achievement for the 2020 Debt to EBITDA Ratio Performance Condition, the 2020 Market Condition, and the extent to which the service vesting condition is satisfied. The estimate of the number of 2020 Performance-Based RSUs earned is evaluated quarterly during the performance period based on our estimate for each of the performance conditions measured against the applicable goals. Compensation expense for the 2020 Performance-Based RSU grant is recognized on a straight-line basis over the requisite service period for each participant, which is generally the three year service period. The 2019 Performance-Based RSUs are scheduled to vest at the end of a three year period (consisting of calendar years 2019-2021). A target number of 2019 Performance-Based RSUs were awarded, and the final number of 2019 Performance-Based RSUs that vest (which may be more or less than the target number) will be based upon (1) the achievement of pre-set FFO per share goals for the year ending December 31, 2019 that applies to 100% of the Performance-Based RSUs awarded (the “2019 FFO Performance Condition”) and (2) a performance measure that applies to 50% of the award based upon a measure of the Company’s average debt to EBITDA ratio for the three year performance period (the “2019 Debt to EBITDA Ratio Performance Condition”) and a market measure that applies to the other 50% of the award based upon the relative ranking of the Company’s total stockholder return for the three year performance period compared to the total stockholder returns of an established comparison group of companies over the same period (the “2019 Market Condition”). The 2019 Performance-Based RSUs are also subject to a three year service vesting provision (the “service vesting condition”) and are scheduled to cliff vest on the date the final vesting percentage is determined following the end of the three year performance period under the awards. The 2019 FFO Performance Condition was achieved at 175% of target for one participant and 150% of target for all other participants. The number of 2019 Performance-Based RSUs ultimately earned could fluctuate from the target number of 2019 Performance-Based RSUs granted based upon the levels of achievement for the 2019 Debt to EBITDA Ratio Performance Condition, the 2019 Market Condition, and the extent to which the service vesting condition is satisfied. The estimate of the number of 2019 Performance-Based RSUs earned is evaluated quarterly during the performance period based on our estimate for each of the performance conditions measured against the applicable goals. Compensation expense for the 2019 Performance-Based RSU grant is recognized on a straight-line basis over the requisite service period for each participant, which is generally the three year service period. The 2018 Performance-Based RSUs are scheduled to vest at the end of a three year period (consisting of calendar years 2018-2020). A target number of 2018 Performance-Based RSUs were awarded, and the final number of 2018 Performance-Based RSUs that vest (which may be more or less than the target number) will be based upon (1) the achievement of pre-set FFO per share goals for the year ending December 31, 2018 that applies to 100% of the Performance-Based RSUs awarded (the “2018 FFO Performance Condition”) and (2) a performance measure that applies to 50% of the award based upon a measure of the Company’s average debt to EBITDA ratio for the three year performance period (the “2018 Debt to EBITDA Ratio Performance Condition” and together with the 2018 FFO Performance Condition, the “2018 Performance Conditions”) and a market measure that applies to the other 50% of the award based upon the relative ranking of the Company’s TSR for the three year performance period compared to the TSR of an established comparison group of companies over the same period (the “2018 Market Condition”). Based on the combined results of the 2018 Performance Conditions and the 2018 Market Condition, the 2018 Performance-Based RSUs achieved a weighted average of 219% for one participant and 175% for the others of their target level of performance. As of December 31, 2020, the estimated number of RSUs earned for the 2020 and 2019 Performance-Based RSUs and the actual number of RSUs earned for the 2018 Performance-Based RSUs was as follows: 2020 Performance-Based RSUs 2019 Performance-Based RSUs 2018 Performance-Based RSUs Service vesting period January 31, 2020 - January, 2023 February 1, 2019 - January, 2022 February 14, 2018 - January, 2021 Target RSUs granted 154,267 143,396 158,205 Estimated RSUs earned (1) 142,004 220,151 229,748 Date of valuation January 31, 2020 February 1, 2019 February 14, 2018 _____________________ (1) Estimated RSUs earned for the 2020 Performance-Based RSUs are based on the actual achievement of the 2020 FFO Performance Condition and for the 2020 Debt to EBITDA Ratio Performance Condition, assumes 100% of the target level of achievement for all participants, and target level of achievement of the 2020 Market Condition. Estimated RSUs earned for the 2019 Performance-Based RSUs are based on the actual achievement of the 2019 FFO Performance Condition and assume target level achievement of the 2019 Market Condition and maximum level of achievement of the 2019 Debt to EBITDA Ratio Performance Condition. The 2018 Performance-Based RSUs earned are based on actual performance of the 2018 Performance Conditions and the 2018 Market Condition. Each Performance-Based RSU represents the right to receive one share of our common stock in the future, subject to, and as modified by, the Company’s level of achievement of the applicable performance and market conditions. The fair values of the 2020 Performance-Based RSUs, 2019 Performance-Based RSUs and 2018 Performance-Based RSUs were $12.9 million at January 31, 2020, $10.2 million at February 1, 2019, and $10.8 million at February 14, 2018, respectively. The fair values for the awards with market conditions were calculated using a Monte Carlo simulation pricing model based on the assumptions in the table below. The determination of the fair value of the 2020, 2019 and 2018 Performance-Based RSUs takes into consideration the likelihood of achievement of the 2020, 2019 and 2018 Performance Conditions and the 2020, 2019 and 2018 Market Conditions, respectively, as discussed above. The following table summarizes the assumptions utilized in the Monte Carlo simulation pricing models: 2020 Award Fair Value Assumptions 2019 Award Fair Value Assumptions 2018 Award Fair Value Assumptions Valuation date January 31, 2020 February 1, 2019 February 14, 2018 Fair value per share on valuation date $84.54 $72.57 $70.08 Expected share price volatility 17.0% 19.0% 20.0% Risk-free interest rate 1.35% 2.48% 2.37% The computation of expected volatility was based on a blend of the historical volatility of our shares of common stock over a period of twice the remaining performance period as of the grant date and implied volatility data based on the observed pricing of six month publicly-traded options on shares of our common stock. The risk-free interest rate was based on the yield curve on zero-coupon U.S. Treasury STRIP securities in effect at January 31, 2020, February 1, 2019, and February 14, 2018. Compensation expense for the Performance-Based RSUs is recognized on a straight-line basis over the requisite service period for each participant, which is generally the three-year service period. As of December 31, 2020, the number of 2020 Performance-Based RSUs estimated to be earned based on the Company’s estimate of the performance conditions measured against the applicable goals was 142,004, and the compensation cost recorded to date for this program was based on that estimate. For the portion of the 2020 Performance-Based RSUs subject to the 2020 Market Condition, for the year ended December 31, 2020, we recorded compensation expense based upon the $84.54 fair value per share at January 31, 2020. Compensation expense will be variable for the portion of the 2020 Performance-Based RSUs subject to the 2020 Debt to EBITDA Ratio Performance Condition, based upon the outcome of that condition. As of December 31, 2020, the number of 2019 Performance-Based RSUs estimated to be earned based on the Company’s estimate of the performance conditions measured against the applicable goals was 220,151, and the compensation cost recorded to date for this program was based on that estimate. For the portion of the 2019 Performance-Based RSUs subject to the 2019 Market Condition, for the years ended December 31, 2020 and 2019, we recorded compensation expense based upon the $72.57 fair value per share at February 1, 2019. Compensation expense will be variable for the portion of the 2019 Performance-Based RSUs subject to the 2019 Debt to EBITDA Performance Condition, based upon the outcome of that condition. For the years ended December 31, 2020, 2019 and 2018, we recorded compensation expense for the portion of the 2018 Performance-Based RSUs subject to the 2018 Market Condition based upon the $70.08 fair value per share at February 14, 2018 and for the portion of the 2018 Performance-Based RSUs subject to the 2018 Debt to EBITDA Ratio Performance Condition, based on the stock price at date of grant multiplied by the number of RSUs estimated to be earned at December 31 of each year. As of December 31, 2020, net of forfeitures, 229,748 RSUs were estimated to be earned. Annual 2020, 2019 and 2018 and December 2018 Time-Based RSU Grants The annual 2020, 2019 and 2018 Time-Based RSUs are scheduled to vest in equal installments over the periods listed below. The 2020 Time-Based RSUs are scheduled to vest in three equal annual installments beginning on January 5, 2021 through January 5, 2023. The 2019 Time-Based RSUs are scheduled to vest in three equal annual installments beginning on January 5, 2020 through January 5, 2022. The December 2018 Time-Based RSUs are scheduled to vest 50% on January 5, 2022 and 50% on January 5, 2023. The 2018 Time-Based RSUs are scheduled to vest in three equal annual installments beginning on January 5, 2019 through January 5, 2021. Compensation expense for the December 2018 and annual 2020, 2019 and 2018 Time-Based RSUs is recognized on a straight-line basis over the requisite service period, which is generally the explicit service period. However, for one participant there is a shorter service period for their December 2018 Time-Based RSUs. Each Time-Based RSU represents the right to receive one share of our common stock in the future, subject to continued employment through the applicable vesting date, unless accelerated upon separation of employment. During the year ended December 31, 2020, the vesting of 54,735 Time-Based RSUs was accelerated due to separation of employment. The total fair value of the Time-Based RSUs is based on the Company's closing share price on the NYSE on the respective fair valuation dates as detailed in the table below: 2020 Time-Based RSU Grant 2019 Time-Based RSU Grant December 2018 Time-Based RSU Grant 2018 Time-Based RSU Grant (1) Service vesting period January 31, 2020 - January 5, 2023 February 1, 2019 - January 5, 2022 December 27, 2018 - January 5, 2023 January & February 2018 - January 5, 2021 Fair value on valuation date (in millions) $ 9.0 $ 10.1 $ 18.5 $ 8.4 Fair value per share $ 82.57 $ 69.89 $ 62.00 $ 70.37 Date of fair valuation January 31, 2020 February 1, 2019 December 27, 2018 January & February 2018 ____________________ (1) The 2018 Time-Based RSUs consist of 56,015 RSUs granted on January 29, 2018 at a fair value per share of $70.37 and 67,818 RSUs granted on February 14, 2018 at a fair value per share of $66.46. Summary of Performance and Market-Measure Based RSUs A summary of our performance and market-measure based RSU activity from January 1, 2020 through December 31, 2020 is presented below: Nonvested RSUs Vested RSUs Total RSUs Amount Weighted-Average Outstanding at January 1, 2020 932,675 $ 71.04 36,679 969,354 Granted 154,267 85.08 38,313 192,580 Vested (230,334) 74.71 230,334 — Settled (1) — — (259,954) (259,954) Issuance of dividend equivalents (2) 29,561 62.21 1,407 30,968 Forfeited (12,460) 84.54 (4) (12,464) Outstanding as of December 31, 2020 (3) 873,709 $ 72.06 46,775 920,484 ____________________ (1) Represents vested RSUs that were settled in shares of the Company’s common stock. Total shares settled include 125,928 shares that were tendered in accordance with the terms of the 2006 Plan to satisfy minimum statutory tax withholding requirements related to the RSUs settled. We accept the return of RSUs at the current quoted closing share price of the Company’s common stock to satisfy tax obligations. (2) Represents the issuance of dividend equivalents earned on the underlying RSUs. The dividend equivalents vest based on terms specified under the related RSU award agreement. (3) Outstanding RSUs as of December 31, 2020 represent the actual achievement of the FFO performance conditions and assumes target levels for the market and other performance conditions. The number of restricted stock units ultimately earned is subject to change based upon actual performance over the three-year vesting period. Dividend equivalents earned will vest along with the underlying award and are also subject to changes based on the number of RSUs ultimately earned for each underlying award. A summary of our performance and market-measure based RSU activity for the years ended December 31, 2020, 2019 and 2018 is presented below: RSUs Granted RSUs Vested Years ended December 31, Non-Vested RSUs Granted (1) Weighted-Average Vested RSUs Total Vest-Date Fair Value 2020 154,267 $ 85.08 (270,054) $ 19,471 2019 231,191 71.12 (265,737) 18,703 2018 601,012 68.51 (265,918) 18,906 ____________________ (1) Non-vested RSUs granted are based on the actual achievement of the FFO performance conditions and assumes target level achievement for the market and other performance conditions. Summary of Time-Based RSUs A summary of our time-based RSU activity from January 1, 2020 through December 31, 2020 is presented below: Nonvested RSUs Vested RSUs Total RSUs Amount Weighted Average Fair Value Outstanding at January 1, 2020 543,848 $ 66.66 1,071,378 1,615,226 Granted 120,769 79.74 — 120,769 Vested (173,796) 70.83 173,796 — Settled (1) (181,462) (181,462) Issuance of dividend equivalents (2) 15,523 61.80 34,812 50,335 Forfeited (11,979) 77.58 — (11,979) Canceled (3) (1,638) (1,638) Outstanding as of December 31, 2020 494,365 $ 67.97 1,096,886 1,591,251 ____________________ (1) Represents vested RSUs that were settled in shares of the Company’s common stock. Total shares settled include 67,316 shares that were tendered in accordance with the terms of the 2006 Plan to satisfy minimum statutory tax withholding requirements related to the RSUs settled. We accept the return of RSUs at the current quoted closing share price of the Company’s common stock to satisfy tax obligations. (2) Represents the issuance of dividend equivalents earned on the underlying RSUs. The dividend equivalents vest based on terms specified under the related RSU award agreement. (3) For shares vested but not yet settled, we accept the return of RSUs at the current quoted closing share price of the Company’s common stock to satisfy minimum statutory tax-withholding requirements related to either the settlement or vesting of RSUs in accordance with the terms of the 2006 Plan. A summary of our time-based RSU activity for the years ended December 31, 2020, 2019 and 2018 is presented below: RSUs Granted RSUs Vested Year ended December 31, Non-Vested Weighted-Average Grant Date Vested RSUs Total Vest-Date Fair Value (1) (in thousands) 2020 120,769 $ 79.74 (208,608) $ 15,066 2019 153,005 70.31 (182,219) 12,227 2018 437,216 64.21 (214,131) 14,768 ____________________ (1) Total fair value of RSUs vested was calculated based on the quoted closing share price of the Company’s common stock on the NYSE on the day of vesting. Excludes the issuance of dividend equivalents earned on the underlying RSUs. The dividend equivalents vest based on terms specified under the related RSU award agreement. Summary of Nonvested Restricted Stock We did not have any nonvested restricted stock at January 1, 2020 and 2019 or December 31, 2020 and 2019. A summary of our nonvested and vested restricted stock activity for the year ended December 31, 2018 is presented below: Shares Granted Shares Vested Years ended December 31, Nonvested Weighted-Average Grant Date Vested Shares Total Fair Value at Vest Date (1) (in thousands) 2018 — — (22,884) 1,652 _______________________ (1) Total fair value of shares vested was calculated based on the quoted closing share price of the Company’s common stock on the NYSE on the date of vesting. Share-Based Compensation Cost Recorded During the Period Share-based compensation costs for the year ended December 31, 2020 include $4.5 million of accelerated share-based compensation costs related to severance packages, including for the departure of an executive officer. The total compensation cost for all share-based compensation programs was $37.6 million, $32.8 million and $35.9 million for the years ended December 31, 2020, 2019 and 2018, respectively. Of the total share-based compensation costs, $7.4 million, $5.8 million and $8.0 million was capitalized as part of real estate assets and for 2018, deferred leasing costs, for the years ended December 31, 2020, 2019 and 2018, respectively. As of December 31, 2020, there was approximately $35.1 million of total unrecognized compensation cost related to nonvested incentive awards granted under share-based compensation arrangements that is expected to be recognized over a weighted-average period of 1.4 years. The remaining compensation cost related to these nonvested incentive awards had been recognized in periods prior to December 31, 2020. The $35.1 million of unrecognized compensation costs does not reflect the future compensation cost related to share-based awards that were granted subsequent to December 31, 2020. Severance Compensation For the year ended December 31, 2020, compensation costs included in general and administrative expenses on our consolidated statements of operations include $14.1 million of cash severance costs related to the departure of an executive officer, in addition to the accelerated share-based compensation costs noted in the paragraph above. Other Compensation

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2020
Retirement Benefits [Abstract]
Employee Benefit Plans	Employee Benefit Plans 401(k) Plan We have a retirement savings plan designed to qualify under Section 401(k) of the Code (the “401(k) Plan”). Our employees are eligible to participate in the 401(k) Plan on the first day of the month after three months of service. The 401(k) Plan allows eligible employees (“401(k) Participants”) to defer up to 60% of their eligible compensation on a pre-tax basis, subject to certain maximum amounts allowed by the Code. The 401(k) Plan provides for a matching contribution by the Company in an amount equal to 50 cents of each one dollar of participant contributions up to a maximum of 10% of the 401(k) Participant’s annual salary. 401(k) Participants vest immediately in the amounts contributed by us. For each of the years ended December 31, 2020, 2019, and 2018, we contributed $1.6 million, $1.6 million and $1.5 million, respectively, to the 401(k) Plan. Deferred Compensation Plan In 2007, we adopted the Deferred Compensation Plan, under which directors and certain management employees may defer receipt of their compensation, including up to 70% of their salaries and up to 100% of their director fees and bonuses, as applicable. In addition, employee participants will receive mandatory Company contributions to their Deferred Compensation Plan accounts equal to 10% of their gross monthly salaries, without regard to whether such employees elect to defer salary or bonus compensation under the Deferred Compensation Plan. Our Board may, but has no obligation to, approve additional discretionary contributions by the Company to Participant accounts. We hold the Deferred Compensation Plan assets in a limited rabbi trust, which is subject to the claims of our creditors in the event of bankruptcy or insolvency. See Note 19 “Fair Value Measurements and Disclosures” for further discussion of our Deferred Compensation Plan assets as of December 31, 2020 and 2019. Our liability of $27.4 million and $27.0 million under the Deferred Compensation Plan was fully funded as of December 31, 2020 and 2019, respectively.

Rental Income and Future Minimu

Rental Income and Future Minimum Rent	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Rental Income and Future Minimum Rent	Rental Income and Future Minimum Rent Our rental income is primarily comprised of payments defined under leases and are either subject to scheduled fixed increases or adjustments in rent based on the Consumer Price Index. Additionally, rental income includes variable payments for tenant reimbursements of property-related expenses and payments based on a percentage of tenant’s sales. The table below sets forth the allocation of rental income between fixed and variable payments and net collectability reversals or recoveries for the years ended December 31, 2020 and 2019: Year Ended December 31, 2020 2019 Fixed lease payments $ 786,860 $ 708,362 Variable lease payments 124,443 115,915 Net collectability (reversals) recoveries (1) (18,997) 2,195 Total rental income $ 892,306 $ 826,472 ____________________ (1) Represents adjustments to rental income related to our assessment of the collectability of amounts due under leases with our tenants. For the year ended December 31, 2020, includes $18.4 million of write - offs related to the cumulative impact of transitioning certain tenants to a cash basis of reporting primarily as a result of the COVID-19 pandemic. Also includes a $0.6 million net increase to the allowance for doubtful accounts, which includes the impact of $2.2 million of reversals to the allowance for doubtful account for tenants that had an allowance at January 1, 2020 and were subsequently transitioned to a cash basis of reporting during 2020. These reversals are included in the $18.4 million of write - offs above. We have operating leases with tenants that expire at various dates through 2044 and are either subject to scheduled fixed increases or adjustments in rent based on the Consumer Price Index. Generally, the leases grant tenants renewal options. Leases also provide for additional rents based on certain operating expenses. Future contractual minimum rent under operating leases, which includes amounts contractually due from leases that are on a cash basis of reporting due to creditworthiness considerations, as of December 31, 2020 for future periods is summarized as follows: Year Ending (in thousands) 2021 $ 731,169 2022 804,488 2023 788,214 2024 750,051 2025 719,274 Thereafter 3,455,201 Total (1) $ 7,248,397 ____________________ (1) Excludes residential leases and leases with a term of one year or less.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies General As of December 31, 2020, we had commitments of approximately $614.9 million, excluding our ground lease commitments, for contracts and executed leases directly related to our operating and development properties. Ground Leases The following table summarizes our properties that are held subject to long-term noncancellable ground lease obligations and the respective contractual expiration dates: Property Contractual Expiration Date (1) 601 108th Ave NE, Bellevue, WA November 2093 701, 801 and 837 N. 34th Street, Seattle, WA (2) December 2041 1701 Page Mill Road and 3150 Porter Drive, Palo Alto, CA December 2067 Kilroy Airport Center Phases I, II, and III, Long Beach, CA July 2084 3243 S. La Cienega Boulevard, Los Angeles, CA (3) October 2106 ____________________ (1) Reflects the contractual expiration date prior to the impact of any extension or purchase options held by the Company. (2) The Company has three 10-year and one 45-year extension options for this ground lease, which if exercised would extend the expiration date to December 2116. These extension options are not assumed to be exercised in our calculation of the present value of the future minimum lease payments for this lease. (3) We entered into this ground lease in connection with an operating property acquisition in 2019. Refer to Note 3 “Acquisitions” for additional information. To determine the discount rates used to calculate the present value of the minimum future lease payments for our ground leases, we used a hypothetical curve derived from unsecured corporate borrowing rates over the lease term. The weighted average discount rate used to determine the present value of our minimum lease payments was 5.11%. As of December 31, 2020, the weighted average remaining lease term of our ground leases is 54 years. For the years ended December 31, 2020 and 2019, variable lease costs totaling $3.0 million and $2.9 million, respectively, were recorded to ground leases expense on our consolidated statements of operations. The minimum commitment under our ground leases as of December 31, 2020 for future periods is as follows: Year Ending (in thousands) 2021 $ 5,641 2022 5,642 2023 5,662 2024 5,662 2025 5,662 Thereafter 280,723 Total undiscounted cash flows (1)(2)(3)(4)(5)(6) $ 308,992 Present value discount (211,214) Ground lease liabilities $ 97,778 ________________________ (1) Excludes contingent future rent payments based on gross income or adjusted gross income and reflects the minimum ground lease obligations before the impact of ground lease extension options. (2) One of our ground lease obligations is subject to a fair market value adjustment every five years; however, the lease includes ground rent subprotection and infrastructure rent credits which currently limit our annual rental obligations to $1.0 million. The contractual obligations for that ground lease included above assumes the lesser of $1.0 million or annual lease rental obligation in effect as of December 31, 2020. (3) One of our ground lease obligations includes a component which is based on the percentage of gross income that exceeds the minimum ground rent. The minimum rent is subject to increases every five years based on 50% of the average annual percentage rent for the previous five years. The contractual obligations for that lease included above assume the current annual ground lease obligation in effect at December 31, 2020 for the remainder of the lease term since we cannot predict future adjustments. (4) One of our ground lease obligations is subject to a fair market value adjustment every five years based on a combination of CPI adjustments and third-party appraisals limited to maximum increases annually. The contractual obligations for that lease included above assume the current annual ground lease obligation in effect at December 31, 2020 for the remainder of the lease term since we cannot predict future adjustments. (5) One of our ground lease obligations includes a component which is based on the percentage of adjusted gross income that exceeds the minimum ground rent. The minimum rent is subject to increases every 10 years by an amount equal to 60% of the average annual percentage rent for the previous three years. The contractual obligations for this lease included above assume the current annual ground lease obligation in effect at December 31, 2020 for the remainder of the lease term since we cannot predict future adjustments. (6) One of our ground lease obligations is subject to fixed 5% ground rent increases every five years, with the next increase occurring on December 1, 2022. Environmental Matters We follow the policy of monitoring all of our properties, including acquisition, development, and existing stabilized portfolio properties, for the presence of hazardous or toxic substances. While there can be no assurance that a material environmental liability does not exist, we are not currently aware of any environmental liability with respect to our stabilized portfolio properties that would have a material adverse effect on our financial condition, results of operations and cash flow, or that we believe would require additional disclosure or the recording of a loss contingency. As of December 31, 2020 and 2019, we had accrued environmental remediation liabilities of approximately $71.3 million and $80.7 million, respectively, recorded on our consolidated balance sheets in connection with certain of our in-process and future development projects. The accrued environmental remediation liabilities represent the remaining costs we estimate we will incur prior to and during the development process at various development acquisition sites. These estimates, which we developed with the assistance of third party experts, consist primarily of the removal of contaminated soil, performing environmental closure activities, constructing remedial systems, and other related costs since we are required to dispose of any existing contaminated soil, and sometimes perform other environmental closure or remedial activities, when we develop new buildings at these sites. We record estimated environmental remediation obligations for acquired properties at the acquisition date when we are aware of such costs and when such costs are probable of being incurred and can be reasonably estimated. Estimated costs related to development environmental remediation liabilities are recorded as an increase to the cost of the development project. Actual costs are recorded as a decrease to the liability when incurred. These accruals are adjusted as an increase or decrease to the development project costs and as an increase or decrease to the accrued environmental remediation liability if we obtain further information or circumstances change. The environmental remediation obligations recorded at December 31, 2020 and 2019 were not discounted to their present values since the amount and timing of cash payments are not fixed. It is possible that we could incur additional environmental remediation costs in connection with these development projects. However, potential additional environmental costs for these development projects cannot be reasonably estimated at this time and certain changes in estimates could occur as the site conditions, final project timing, design elements, actual soil conditions and other aspects of the projects, which may depend upon municipal and other approvals beyond the control of the Company, are determined. Other than the accrued environmental liabilities discussed above, we are not aware of any unasserted claims and assessments with respect to an environmental liability that we believe would require additional disclosure or the recording of an additional loss contingency. Litigation We and our properties are subject to litigation arising in the ordinary course of business. To our knowledge, neither we nor any of our properties are presently subject to any litigation or threat of litigation which, if determined unfavorably to us, would have a material adverse effect on our cash flow, financial condition, or results of operations. Insurance

Fair Value Measurements and Dis

Fair Value Measurements and Disclosures	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements and Disclosures	Fair Value Measurements and Disclosures Assets and Liabilities Reported at Fair Value The only assets we record at fair value on our consolidated financial statements are the marketable securities related to our Deferred Compensation Plan (see Note 16 “Employee Benefit Plans” for additional information). The following table sets forth the fair value of our marketable securities as of December 31, 2020 and 2019: Fair Value (Level 1) (1) 2020 2019 Description (in thousands) Marketable securities (2) $ 27,481 $ 27,098 ____________________ (1) Based on quoted prices in active markets for identical securities. (2) The marketable securities are held in a limited rabbi trust . We report the change in the fair value of the marketable securities at the end of each accounting period in interest income and other net investment gain (loss) in the consolidated statements of operations. We also adjust the related Deferred Compensation Plan liability to fair value at the end of each accounting period based on the performance of the benchmark funds selected by each participant, which results in a corresponding increase or decrease to compensation cost included in general and administrative expenses on our consolidated statements of operations for the period. The following table sets forth the net gain (loss) on marketable securities recorded during the years ended December 31, 2020, 2019 and 2018: December 31, 2020 2019 2018 Description (in thousands) Net gain (loss) on marketable securities $ 2,864 $ 3,885 $ (1,851) Financial Instruments Disclosed at Fair Value The following table sets forth the carrying value and the fair value of our other financial instruments as of December 31, 2020 and 2019: December 31, 2020 2019 Carrying Value Fair Value (1) Carrying Value Fair Value (1) (in thousands) Liabilities Secured debt, net $ 253,582 $ 282,559 $ 258,593 $ 272,997 Unsecured debt, net 3,670,099 4,089,339 3,049,185 3,252,217 Unsecured line of credit — — 245,000 245,195 _______________ (1) Fair value calculated using Level II inputs, which are based on model-derived valuations in which significant inputs and significant value drivers are observable in active markets.

Net Income Available to Common

Net Income Available to Common Stockholders Per Share of the Company	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Net Income Available to Common Stockholders Per Share of the Company	Net Income Available to Common Stockholders Per Share of the Company The following table reconciles the numerator and denominator in computing the Company’s basic and diluted per-share computations for net income available to common stockholders for the years ended December 31, 2020, 2019 and 2018: Year Ended December 31, 2020 2019 2018 (in thousands, except unit and per unit amounts) Numerator: Net income attributable to common stockholders $ 187,105 $ 195,443 $ 258,415 Allocation to participating securities (1) (2,229) (2,119) (2,004) Numerator for basic and diluted net income available to common stockholders $ 184,876 $ 193,324 $ 256,411 Denominator: Basic weighted average vested shares outstanding 113,241,341 103,200,568 99,972,359 Effect of dilutive securities 478,281 648,600 510,006 Diluted weighted average vested shares and common stock equivalents outstanding 113,719,622 103,849,168 100,482,365 Basic earnings per share: Net income available to common stockholders per share $ 1.63 $ 1.87 $ 2.56 Diluted earnings per share: Net income available to common stockholders per share $ 1.63 $ 1.86 $ 2.55 _____________________ (1) Participating securities include nonvested shares, certain time-based RSUs and vested market measure-based RSUs. Share-based payment awards that contain non-forfeitable rights to dividends or dividend equivalents (whether paid or unpaid) are considered participating securities. The impact of potentially dilutive common shares, including stock options, RSUs, shares issuable under executed forward equity sale agreements, if any, and other securities are considered in our diluted earnings per share calculation for the years ended December 31, 2020, 2019, and 2018. Certain market measure-based RSUs are not included in dilutive securities as of December 31, 2020, 2019, and 2018 as not all performance metrics had been met by the end of the applicable reporting periods.

Net Income Available to Commo_2

Net Income Available to Common Unitholders Per Unit of the Operating Partnership	12 Months Ended
	Dec. 31, 2020
Kilroy Realty L.P. [Member]
Net Income Available To Common Unitholders [Line Items]
Net Income Available to Common Unitholders per Unit of the Operating Partnership	Net Income Available to Common Unitholders Per Unit of the Operating Partnership The following table reconciles the numerator and denominator in computing the Operating Partnership’s basic and diluted per-unit computations for net income available to common unitholders for the years ended December 31, 2020, 2019 and 2018: Year Ended December 31, 2020 2019 2018 (in thousands, except unit and per unit amounts) Numerator: Net income attributable to common unitholders $ 189,609 $ 198,738 $ 263,210 Allocation to participating securities (1) (2,229) (2,119) (2,004) Numerator for basic and diluted net income available to common unitholders $ 187,380 $ 196,619 $ 261,206 Denominator: Basic weighted average vested units outstanding 115,095,506 105,223,975 102,025,276 Effect of dilutive securities 478,281 648,600 510,006 Diluted weighted average vested units and common unit equivalents outstanding 115,573,787 105,872,575 102,535,282 Basic earnings per unit: Net income available to common unitholders per unit $ 1.63 $ 1.87 $ 2.56 Diluted earnings per unit: Net income available to common unitholders per unit $ 1.62 $ 1.86 $ 2.55 ____________________ (1) Participating securities include nonvested shares, certain time-based RSUs and vested market measure-based RSUs. Share-based payment awards that contain non-forfeitable rights to dividends or dividend equivalents (whether paid or unpaid) are considered participating securities. The impact of potentially dilutive common units, including stock options, RSUs, shares issuable under executed forward equity sale agreements, if any, and other securities are considered in our diluted earnings per share calculation for the years ended December 31, 2020, 2019 and 2018. Certain market measure-based RSUs are not included in dilutive securities as of December 31, 2020, 2019 and 2018 as not all performance metrics had been met by the end of the applicable reporting periods.

Supplemental Cash Flow Informat

Supplemental Cash Flow Information of the Company	12 Months Ended
	Dec. 31, 2020
Supplemental Cash Flow Elements [Abstract]
Supplemental Cash Flow Information of the Company	Supplemental Cash Flow Information of the Company Supplemental cash flow information follows (in thousands): Year Ended December 31, 2020 2019 2018 SUPPLEMENTAL CASH FLOWS INFORMATION: Cash paid for interest, net of capitalized interest of $75,852, $77,666, and $65,627 as of December 31, 2020, 2019 and 2018, respectively $ 61,741 $ 43,607 $ 44,697 Cash paid for amounts included in the measurement of ground lease liabilities $ 5,744 $ 5,224 $ 4,398 NON-CASH INVESTING TRANSACTIONS: Accrual for expenditures for operating properties and development properties $ 189,161 $ 162,654 $ 158,626 Tenant improvements funded directly by tenants $ 11,592 $ 10,268 $ 13,968 Assumption of accrued liabilities in connection with acquisitions (Note 3) $ — $ 10,267 $ 40,624 Initial measurement of operating right of use ground lease assets (Notes 2, 3 and 18) $ — $ 96,272 $ — Initial measurement of operating ground lease liabilities (Notes 2, 3 and 18) $ — $ 98,349 $ — NON-CASH FINANCING TRANSACTIONS: Accrual of dividends and distributions payable to common stockholders and common $ 59,431 $ 53,219 $ 47,559 Exchange of common units of the Operating Partnership into shares of the Company’s $ 37,640 $ 78 $ 1,962 The following is a reconciliation of our cash and cash equivalents and restricted cash at the beginning and end of the years ended December 31, 2020, 2019 and 2018. Year Ended December 31, 2020 2019 2018 RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH: Cash and cash equivalents at beginning of period $ 60,044 $ 51,604 $ 57,649 Restricted cash at beginning of period 16,300 119,430 9,149 Cash and cash equivalents and restricted cash at beginning of period $ 76,344 $ 171,034 $ 66,798 Cash and cash equivalents at end of period $ 731,991 $ 60,044 $ 51,604 Restricted cash at end of period 91,139 16,300 119,430 Cash and cash equivalents and restricted cash at end of period $ 823,130 $ 76,344 $ 171,034 Supplemental cash flow information follows (in thousands): Year Ended December 31, 2020 2019 2018 SUPPLEMENTAL CASH FLOWS INFORMATION: Cash paid for interest, net of capitalized interest of $75,852, $77,666, and $65,627 as of December 31, 2020, 2019 and 2018, respectively $ 61,741 $ 43,607 $ 44,697 Cash paid for amounts included in the measurement of ground lease liabilities $ 5,744 $ 5,224 $ 4,398 NON-CASH INVESTING TRANSACTIONS: Accrual for expenditures for operating properties and development properties $ 189,161 $ 162,654 $ 158,626 Tenant improvements funded directly by tenants $ 11,592 $ 10,268 $ 13,968 Assumption of accrued liabilities in connection with acquisitions (Note 3) $ — $ 10,267 $ 40,624 Initial measurement of operating right of use ground lease assets (Notes 2, 3 and 18) $ — $ 96,272 $ — Initial measurement of operating ground lease liabilities (Notes 2, 3 and 18) $ — $ 98,349 $ — NON-CASH FINANCING TRANSACTIONS: Accrual of distributions payable to common unitholders (Notes 14 and 27) $ 59,431 $ 53,219 $ 47,559 The following is a reconciliation of our cash and cash equivalents and restricted cash at the beginning and end of the years ended December 31, 2020, 2019 and 2018. Year Ended December 31, 2020 2019 2018 RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH: Cash and cash equivalents at beginning of period $ 60,044 $ 51,604 $ 57,649 Restricted cash at beginning of period 16,300 119,430 9,149 Cash and cash equivalents and restricted cash at beginning of period $ 76,344 $ 171,034 $ 66,798 Cash and cash equivalents at end of period $ 731,991 $ 60,044 $ 51,604 Restricted cash at end of period 91,139 16,300 119,430 Cash and cash equivalents and restricted cash at end of period $ 823,130 $ 76,344 $ 171,034

Supplemental Cash Flow Inform_2

Supplemental Cash Flow Information of the Operating Partnership	12 Months Ended
	Dec. 31, 2020
Supplemental Cash Flow Elements [Abstract]
Supplemental Cash Flow Information of the Operating Partnership	Supplemental Cash Flow Information of the Company Supplemental cash flow information follows (in thousands): Year Ended December 31, 2020 2019 2018 SUPPLEMENTAL CASH FLOWS INFORMATION: Cash paid for interest, net of capitalized interest of $75,852, $77,666, and $65,627 as of December 31, 2020, 2019 and 2018, respectively $ 61,741 $ 43,607 $ 44,697 Cash paid for amounts included in the measurement of ground lease liabilities $ 5,744 $ 5,224 $ 4,398 NON-CASH INVESTING TRANSACTIONS: Accrual for expenditures for operating properties and development properties $ 189,161 $ 162,654 $ 158,626 Tenant improvements funded directly by tenants $ 11,592 $ 10,268 $ 13,968 Assumption of accrued liabilities in connection with acquisitions (Note 3) $ — $ 10,267 $ 40,624 Initial measurement of operating right of use ground lease assets (Notes 2, 3 and 18) $ — $ 96,272 $ — Initial measurement of operating ground lease liabilities (Notes 2, 3 and 18) $ — $ 98,349 $ — NON-CASH FINANCING TRANSACTIONS: Accrual of dividends and distributions payable to common stockholders and common $ 59,431 $ 53,219 $ 47,559 Exchange of common units of the Operating Partnership into shares of the Company’s $ 37,640 $ 78 $ 1,962 The following is a reconciliation of our cash and cash equivalents and restricted cash at the beginning and end of the years ended December 31, 2020, 2019 and 2018. Year Ended December 31, 2020 2019 2018 RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH: Cash and cash equivalents at beginning of period $ 60,044 $ 51,604 $ 57,649 Restricted cash at beginning of period 16,300 119,430 9,149 Cash and cash equivalents and restricted cash at beginning of period $ 76,344 $ 171,034 $ 66,798 Cash and cash equivalents at end of period $ 731,991 $ 60,044 $ 51,604 Restricted cash at end of period 91,139 16,300 119,430 Cash and cash equivalents and restricted cash at end of period $ 823,130 $ 76,344 $ 171,034 Supplemental cash flow information follows (in thousands): Year Ended December 31, 2020 2019 2018 SUPPLEMENTAL CASH FLOWS INFORMATION: Cash paid for interest, net of capitalized interest of $75,852, $77,666, and $65,627 as of December 31, 2020, 2019 and 2018, respectively $ 61,741 $ 43,607 $ 44,697 Cash paid for amounts included in the measurement of ground lease liabilities $ 5,744 $ 5,224 $ 4,398 NON-CASH INVESTING TRANSACTIONS: Accrual for expenditures for operating properties and development properties $ 189,161 $ 162,654 $ 158,626 Tenant improvements funded directly by tenants $ 11,592 $ 10,268 $ 13,968 Assumption of accrued liabilities in connection with acquisitions (Note 3) $ — $ 10,267 $ 40,624 Initial measurement of operating right of use ground lease assets (Notes 2, 3 and 18) $ — $ 96,272 $ — Initial measurement of operating ground lease liabilities (Notes 2, 3 and 18) $ — $ 98,349 $ — NON-CASH FINANCING TRANSACTIONS: Accrual of distributions payable to common unitholders (Notes 14 and 27) $ 59,431 $ 53,219 $ 47,559 The following is a reconciliation of our cash and cash equivalents and restricted cash at the beginning and end of the years ended December 31, 2020, 2019 and 2018. Year Ended December 31, 2020 2019 2018 RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH: Cash and cash equivalents at beginning of period $ 60,044 $ 51,604 $ 57,649 Restricted cash at beginning of period 16,300 119,430 9,149 Cash and cash equivalents and restricted cash at beginning of period $ 76,344 $ 171,034 $ 66,798 Cash and cash equivalents at end of period $ 731,991 $ 60,044 $ 51,604 Restricted cash at end of period 91,139 16,300 119,430 Cash and cash equivalents and restricted cash at end of period $ 823,130 $ 76,344 $ 171,034

Tax Treatment of Distributions

Tax Treatment of Distributions	12 Months Ended
	Dec. 31, 2020
Tax Treatment of Distributions [Abstract]
Tax Treatment of Distributions	Tax Treatment of Distributions The following table reconciles the dividends declared per share of common stock to the dividends paid per share of common stock during the years ended December 31, 2020, 2019 and 2018 as follows: Year Ended December 31, Dividends 2020 2019 2018 Dividends declared per share of common stock $ 1.970 $ 1.910 $ 1.790 Less: Dividends declared in the current year and paid in the following year (0.500) (0.485) (0.455) Add: Dividends declared in the prior year and paid in the current year 0.485 0.455 0.425 Dividends paid per share of common stock $ 1.955 $ 1.880 $ 1.760 The unaudited income tax treatment for the dividends to common stockholders reportable for the years ended December 31, 2020, 2019 and 2018 as identified in the table above was as follows: Year Ended December 31, Shares of Common Stock 2020 2019 2018 Ordinary income (1) $ 1.474 75.40 % $ 0.939 49.95 % $ 1.474 83.73 % Qualified dividend 0.002 0.12 0.004 0.21 0.003 0.19 Return of capital 0.162 8.30 0.312 16.62 0.275 15.64 Capital gains (2) 0.275 14.05 0.600 31.93 0.008 0.44 Unrecaptured section 1250 gains 0.042 2.13 0.025 1.29 — — $ 1.955 100.00 % $ 1.880 100.00 % $ 1.760 100.00 % ____________________ (1) The Tax Cuts and Jobs Act enacted on December 22, 2017 generally allows a deduction for noncorporate taxpayers equal to 20% of ordinary dividends distributed by a REIT (excluding capital gain dividends and qualified dividend income). The amount of dividend eligible for this deduction is referred to as the Section 199A Dividend. For the year ended December 31, 2020, the Section 199A Dividend is equal to the total ordinary income dividend. (2) Capital gains are comprised entirely of 20% rate gains.

Quarterly Financial Information

Quarterly Financial Information of the Company (Unaudited)	12 Months Ended
	Dec. 31, 2020
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information of the Company (Unaudited)	Quarterly Financial Information of the Company (Unaudited) Summarized quarterly financial data for the years ended December 31, 2020 and 2019 was as follows: 2020 Quarter Ended (1) March 31, June 30, September 30, December 31, (in thousands, except per share amounts) Revenues $ 221,328 $ 219,423 $ 228,314 $ 229,332 Net income 45,418 24,352 54,071 83,452 Net income attributable to Kilroy Realty Corporation 39,817 19,618 49,028 78,642 Net income available to common stockholders 39,817 19,618 49,028 78,642 Net income available to common stockholders per share – basic 0.37 0.17 0.42 0.67 Net income available to common stockholders per share – diluted 0.37 0.17 0.42 0.67 2019 Quarter Ended (1) March 31, June 30, September 30, December 31, (in thousands, except per share amounts) Revenues $ 201,202 $ 200,492 $ 215,525 $ 220,235 Net income 41,794 47,215 48,298 77,922 Net income attributable to Kilroy Realty Corporation 36,903 42,194 43,846 72,500 Net income available to common stockholders 36,903 42,194 43,846 72,500 Net income available to common stockholders per share – basic 0.36 0.41 0.41 0.68 Net income available to common stockholders per share – diluted 0.36 0.41 0.41 0.67 ____________________

Quarterly Financial Informati_2

Quarterly Financial Information of the Operating Partnership (Unaudited)	12 Months Ended
	Dec. 31, 2020
Quarterly Financial Information of the Operating Partnership (Unaudited)	Quarterly Financial Information of the Company (Unaudited) Summarized quarterly financial data for the years ended December 31, 2020 and 2019 was as follows: 2020 Quarter Ended (1) March 31, June 30, September 30, December 31, (in thousands, except per share amounts) Revenues $ 221,328 $ 219,423 $ 228,314 $ 229,332 Net income 45,418 24,352 54,071 83,452 Net income attributable to Kilroy Realty Corporation 39,817 19,618 49,028 78,642 Net income available to common stockholders 39,817 19,618 49,028 78,642 Net income available to common stockholders per share – basic 0.37 0.17 0.42 0.67 Net income available to common stockholders per share – diluted 0.37 0.17 0.42 0.67 2019 Quarter Ended (1) March 31, June 30, September 30, December 31, (in thousands, except per share amounts) Revenues $ 201,202 $ 200,492 $ 215,525 $ 220,235 Net income 41,794 47,215 48,298 77,922 Net income attributable to Kilroy Realty Corporation 36,903 42,194 43,846 72,500 Net income available to common stockholders 36,903 42,194 43,846 72,500 Net income available to common stockholders per share – basic 0.36 0.41 0.41 0.68 Net income available to common stockholders per share – diluted 0.36 0.41 0.41 0.67 ____________________
Kilroy Realty L.P. [Member]
Quarterly Financial Information of the Operating Partnership (Unaudited)	Quarterly Financial Information of the Operating Partnership (Unaudited) Summarized quarterly financial data for the years ended December 31, 2020 and 2019 was as follows: 2020 Quarter Ended (1) March 31, June 30, September 30, December 31, (in thousands, except per unit amounts) Revenues $ 221,328 $ 219,423 $ 228,314 $ 229,332 Net income 45,418 24,352 54,071 83,452 Net income attributable to the Operating Partnership 40,389 19,838 49,728 79,654 Net income available to common unitholders 40,389 19,838 49,728 79,654 Net income available to common unitholders per unit – basic 0.37 0.16 0.42 0.67 Net income available to common unitholders per unit – diluted 0.36 0.16 0.42 0.67 2019 Quarter Ended (1) March 31, June 30, September 30, December 31, (in thousands, except per unit amounts) Revenues $ 201,202 $ 200,492 $ 215,525 $ 220,235 Net income 41,794 47,215 48,298 77,922 Net income attributable to the Operating Partnership 37,508 42,901 44,589 73,740 Net income available to common unitholders 37,508 42,901 44,589 73,740 Net income available to common unitholders per unit – basic 0.36 0.41 0.41 0.68 Net income available to common unitholders per unit – diluted 0.36 0.41 0.41 0.67 ______________________

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2020
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On January 15, 2021, $59.4 million of dividends were paid out to common stockholders, common unitholders and RSU holders of record on December 31, 2020. On January 29, 2021, the Executive Compensation Committee granted 102,799 Time-Based RSUs to key employees under the 2006 Plan. The compensation cost related to the RSUs is expected to be recognized over a period of three years.

Schedule II - Valuation and Qua

Schedule II - Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2020
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]
Schedule II - Valuation and Qualifying Accounts	SCHEDULE II – VALUATION AND QUALIFYING ACCOUNTS Years ended December 31, 2020, 2019 and 2018 (in thousands) Balance at Beginning of Period (1) Charged to Costs and Expenses (2) Deductions (3) Balance Allowance for Uncollectible Tenant Receivables for the year ended 2020 – Allowance for uncollectible tenant receivables $ 1,171 $ 1,977 $ (1,349) $ 1,799 2019 – Allowance for uncollectible tenant receivables 512 907 (248) 1,171 2018 – Allowance for uncollectible tenant receivables 2,309 2,604 (274) 4,639 Allowance for Deferred Rent Receivables for the year ended 2020 – Allowance for deferred rent $ 1,552 $ 832 $ (1,580) $ 804 2019 – Allowance for deferred rent 195 1,357 — 1,552 2018 – Allowance for deferred rent 3,238 165 (64) 3,339 ____________________ (1) On January 1, 2019, the Company adopted Topic 842 on a modified retrospective basis and recognized a cumulative-effect adjustment to distributions in excess of earnings related to the allowances for uncollectible tenant receivables and deferred rent receivables. As such, the ending balances of the allowances for uncollectible tenant receivables and deferred rent receivables at December 31, 2018 do not equal the beginning balances on January 1, 2019. (2) For the years ended December 31, 2020 and 2019, amounts do not reflect leases deemed not probable of collection for which we reversed the associated revenue under Topic 842. In addition, for the years ended December 31, 2020, 2019 and 2018, $1.7 million, $0.7 million and $2.9 million, respectively, was charged to costs and expenses for a valuation allowance for a note receivable. (3) For the year ended December 31, 2020, includes reversals of allowance for doubtful accounts for tenants with an allowance at January 1, 2020 that were subsequently transitioned to a cash basis of reporting.

Schedule III - Real Estate and

Schedule III - Real Estate and Accumulated Depreciation	12 Months Ended
	Dec. 31, 2020
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation Disclosure [Abstract]
Schedule III - Real Estate and Accumulated Depreciation	SCHEDULE III – REAL ESTATE AND ACCUMULATED DEPRECIATION December 31, 2020 Initial Cost Gross Amounts at Which Property Location Encumb- Land and improve- Buildings Costs Land and improve- Buildings Total Accumulated Depreci- ation Life (1) Date of Acquisition (A)/ Construction (C) (2) Rentable Square Feet (3) (unaudited) ($ in thousands) Office Properties: 3101-3243 S. La Cienega Blvd., Culver City, CA $ 150,718 $ 31,033 $ 227 $ 150,718 $ 31,259 $ 181,977 $ 6,127 35 2019 A 151,908 2240 E. Imperial Highway, El Segundo, CA 1,044 11,763 29,551 1,048 41,310 42,358 28,203 35 1983 C 122,870 2250 E. Imperial Highway, El Segundo, CA 2,579 29,062 36,311 2,547 65,405 67,952 56,603 35 1983 C 298,728 2260 E. Imperial Highway, El Segundo, CA 2,518 28,370 36,781 2,547 65,122 67,669 18,563 35 1983 C 298,728 909 N. Pacific Coast Highway, El Segundo, CA 3,577 34,042 51,773 3,577 85,815 89,392 44,727 35 2005 C 244,136 999 N. Pacific Coast Highway, El Segundo, CA 1,407 34,326 17,295 1,407 51,621 53,028 27,429 35 2003 C 128,588 1350 Ivar Ave., Los Angeles, CA 1,575 — 13,725 1,575 13,725 15,300 65 35 2020 C 16,448 1355 Vine St., Los Angeles, CA 17,588 — 114,603 17,588 114,603 132,191 549 35 2020 C 183,129 1375 Vine St., Los Angeles, CA 15,578 — 97,470 15,578 97,470 113,048 461 35 2020 C 159,236 1395 Vine St., Los Angeles, CA 278 — 3,138 278 3,138 3,417 16 35 2020 C 2,575 6115 W. Sunset Blvd., Los Angeles, CA (4) 1,313 3 16,454 2,455 15,315 17,770 2,787 35 2015 C 26,105 6121 W. Sunset Blvd., Los Angeles, CA (4) 11,120 4,256 43,983 8,703 50,656 59,359 8,894 35 2015 C 91,173 1525 N. Gower St., Los Angeles, CA (4) 1,318 3 9,641 1,318 9,645 10,962 1,542 35 2016 C 9,610 1575 N. Gower St., Los Angeles, CA (4) 22,153 51 119,496 22,153 119,547 141,700 15,482 35 2016 C 251,245 1500 N. El Centro Ave., Los Angeles, CA (4) 9,235 21 58,988 9,235 59,009 68,244 12,666 35 2016 C 104,504 6255 W. Sunset Blvd., Los Angeles, CA 18,111 60,320 49,265 18,111 109,585 127,696 41,735 35 2012 A 323,920 3750 Kilroy Airport Way, Long Beach, CA — 1,941 13,113 — 15,054 15,054 11,247 35 1989 C 10,718 3760 Kilroy Airport Way, Long Beach, CA — 17,467 16,687 — 34,154 34,154 28,166 35 1989 C 166,761 3780 Kilroy Airport Way, Long Beach, CA — 22,319 31,855 — 54,174 54,174 41,573 35 1989 C 221,452 3800 Kilroy Airport Way, Long Beach, CA — 19,408 22,252 — 41,660 41,660 26,473 35 2000 C 192,476 3840 Kilroy Airport Way, Long Beach, CA — 13,586 11,755 — 25,341 25,341 16,793 35 1999 C 136,026 3880 Kilroy Airport Way, Long Beach, CA — 9,704 11,827 — 21,531 21,531 5,220 35 1997 A 96,923 3900 Kilroy Airport Way, Long Beach, CA — 12,615 13,208 — 25,823 25,823 19,261 35 1997 A 130,935 Kilroy Airport Center, Phase IV, Long Beach, CA (5) — — 4,997 — 4,997 4,997 4,997 35 — — 8560 W. Sunset Blvd., West Hollywood, CA 9,720 50,956 1,930 9,720 52,886 62,606 8,351 35 2016 A 74,842 8570 W. Sunset Blvd., West Hollywood, CA 31,693 27,974 6,497 31,693 34,471 66,163 4,121 35 2016 A 45,941 8580 W. Sunset Blvd., West Hollywood, CA 10,013 3,695 1,219 10,013 4,914 14,927 523 35 2016 A 7,126 8590 W. Sunset Blvd., West Hollywood, CA 39,954 27,884 5,487 39,954 33,371 73,325 4,473 35 2016 A 55,302 12100 W. Olympic Blvd., Los Angeles, CA $166,776 (6) 352 45,611 20,191 9,633 56,520 66,154 30,836 35 2003 C 152,048 12200 W. Olympic Blvd., Los Angeles, CA (6) 4,329 35,488 25,506 3,977 61,346 65,323 42,135 35 2000 C 150,832 12233 W. Olympic Blvd., Los Angeles, CA 22,100 53,170 5,258 22,100 58,428 80,528 16,326 35 2012 A 151,029 12312 W. Olympic Blvd., Los Angeles, CA (6) 3,325 12,202 12,345 3,399 24,473 27,872 14,923 35 1997 A 76,644 1633 26th St., Santa Monica, CA 2,080 6,672 4,006 2,040 10,718 12,758 7,497 35 1997 A 43,857 2100/2110 Colorado Ave., Santa Monica, CA 5,474 26,087 14,915 5,476 41,000 46,476 27,393 35 1997 A 102,864 KILROY REALTY CORPORATION AND KILROY REALTY, L.P. SCHEDULE III – REAL ESTATE AND ACCUMULATED DEPRECIATION – (Continued) December 31, 2020 Initial Cost Gross Amounts at Which Property Location Encumb- Land and improve- Buildings Costs Land and improve- Buildings Total Accumulated Depreci- ation Life (1) Date of Acquisition (A)/ Construction (C) (2) Rentable Square Feet (3) (unaudited) ($ in thousands) 3130 Wilshire Blvd., Santa Monica, CA 8,921 6,579 17,147 9,188 23,459 32,647 17,318 35 1997 A 90,074 501 Santa Monica Blvd., Santa Monica, CA 4,547 12,044 16,304 4,551 28,344 32,895 19,067 35 1998 A 76,803 12225 El Camino Real, Del Mar, CA 1,700 9,633 3,864 1,673 13,524 15,197 9,622 35 1998 A 58,401 12235 El Camino Real, Del Mar, CA 1,507 8,543 9,255 1,540 17,765 19,305 11,193 35 1998 A 53,751 12340 El Camino Real, Del Mar, CA 4,201 13,896 12,195 4,201 26,091 30,292 13,226 35 2002 C 89,272 12390 El Camino Real, Del Mar, CA 3,453 11,981 9,541 3,453 21,522 24,975 10,742 35 2000 C 70,140 12348 High Bluff Dr., Del Mar, CA 1,629 3,096 6,890 1,629 9,986 11,615 6,963 35 1999 C 39,193 12400 High Bluff Dr., Del Mar, CA 15,167 40,497 16,850 15,167 57,347 72,514 30,685 35 2004 C 210,732 12770 El Camino Real, Del Mar, CA 9,360 — 34,212 9,360 34,212 43,572 4,493 35 2015 C 73,032 12780 El Camino Real, Del Mar, CA 18,398 54,954 22,922 18,398 77,876 96,274 18,909 35 2013 A 140,591 12790 El Camino Real, Del Mar, CA 10,252 21,236 8,485 10,252 29,721 39,973 6,812 35 2013 A 78,836 12860 El Camino Real, Del Mar, CA (7) — — 60,675 11,326 49,349 60,675 602 35 — — 12830 El Camino Real, Del Mar, CA (7) — — 134,776 28,645 106,131 134,776 885 35 — — 3579 Valley Centre Dr., Del Mar, CA 2,167 6,897 9,559 2,858 15,765 18,623 10,397 35 1999 C 54,960 3611 Valley Centre Dr., Del Mar, CA 4,184 19,352 25,934 5,259 44,212 49,470 27,028 35 2000 C 130,109 3661 Valley Centre Dr., Del Mar, CA 4,038 21,144 18,897 4,725 39,354 44,079 24,083 35 2001 C 128,364 3721 Valley Centre Dr., Del Mar, CA 4,297 18,967 14,973 4,254 33,983 38,237 19,134 35 2003 C 115,193 3811 Valley Centre Dr., Del Mar, CA 3,452 16,152 20,540 4,457 35,687 40,144 24,154 35 2000 C 112,067 3745 Paseo Place, Del Mar, CA (Retail) 24,358 — 72,290 24,358 72,290 96,648 4,435 35 2019 C 95,871 13280 Evening Creek Dr. South, I-15 Corridor, CA 3,701 8,398 4,818 3,701 13,216 16,917 6,354 35 2008 C 41,196 13290 Evening Creek Dr. South, I-15 Corridor, CA 5,229 11,871 6,150 5,229 18,021 23,250 7,665 35 2008 C 61,180 13480 Evening Creek Dr. South, I-15 Corridor, CA 7,997 — 52,581 7,997 52,581 60,578 21,940 35 2008 C 154,157 13500 Evening Creek Dr. South, I-15 Corridor, CA 7,581 35,903 23,609 7,580 59,513 67,093 24,861 35 2004 A 137,658 13520 Evening Creek Dr. South, I-15 Corridor, CA 7,581 35,903 19,454 7,580 55,358 62,938 27,289 35 2004 A 146,701 2305 Historic Decatur Rd., Point Loma, CA 5,240 22,220 7,650 5,240 29,870 35,110 12,291 35 2010 A 107,456 4690 Executive Dr., University Towne Centre, CA 1,623 7,926 3,725 1,623 11,651 13,274 8,314 35 1999 A 47,846 4100 Bohannon Dr., Menlo Park, CA 4,835 15,526 932 4,860 16,433 21,293 5,123 35 2012 A 47,379 4200 Bohannon Dr., Menlo Park, CA 4,798 15,406 3,967 4,662 19,509 24,171 6,585 35 2012 A 45,451 4300 Bohannon Dr., Menlo Park, CA 6,527 20,958 5,373 6,470 26,387 32,858 8,557 35 2012 A 63,079 4400 Bohannon Dr., Menlo Park, CA 4,798 15,406 3,331 4,939 18,597 23,535 6,394 35 2012 A 48,146 4500 Bohannon Dr., Menlo Park, CA 6,527 20,957 3,811 6,470 24,825 31,295 7,506 35 2012 A 63,078 4600 Bohannon Dr., Menlo Park, CA 4,798 15,406 4,025 4,939 19,290 24,229 6,427 35 2012 A 48,147 4700 Bohannon Dr., Menlo Park, CA 6,527 20,958 1,584 6,470 22,599 29,069 7,112 35 2012 A 63,078 1290 - 1300 Terra Bella Ave., Mountain View, CA 28,730 27,555 61 28,730 27,616 56,346 5,702 35 2016 A 114,175 KILROY REALTY CORPORATION AND KILROY REALTY, L.P. SCHEDULE III – REAL ESTATE AND ACCUMULATED DEPRECIATION – (Continued) December 31, 2020 Initial Cost Gross Amounts at Which Property Location Encumb- Land and improve- Buildings Costs Land and improve- Buildings Total Accumulated Depreci- ation Life (1) Date of Acquisition (A)/ Construction (C) (2) Rentable Square Feet (3) (unaudited) ($ in thousands) 680 E. Middlefield Rd., Mountain View, CA 34,605 — 56,522 34,605 56,522 91,127 11,718 35 2014 C 170,090 690 E. Middlefield Rd., Mountain View, CA 34,755 — 56,764 34,755 56,765 91,519 11,768 35 2014 C 170,823 1701 Page Mill Rd., Palo Alto, CA — 99,522 29 — 99,551 99,551 12,005 35 2016 A 128,688 3150 Porter Dr., Palo Alto, CA — 21,715 410 — 22,125 22,125 3,170 35 2016 A 36,886 900 Jefferson Ave., Redwood City, CA (8) 16,668 — 109,377 18,063 107,982 126,045 19,674 35 2015 C 228,505 900 Middlefield Rd., Redwood City, CA (8) 7,959 — 50,115 8,626 49,449 58,074 8,684 35 2015 C 118,764 100 Hooper St., San Francisco, CA 78,564 — 191,895 85,510 184,949 270,459 11,632 35 2018 C 394,340 100 First St., San Francisco, CA (9) 49,150 131,238 73,238 49,150 204,476 253,626 73,294 35 2010 A 480,457 201 Third St., San Francisco, CA 19,260 84,018 69,158 19,260 153,176 172,436 65,165 35 2011 A 346,538 250 Brannan St., San Francisco, CA 7,630 22,770 10,043 7,630 32,813 40,443 11,783 35 2011 A 100,850 301 Brannan St., San Francisco, CA 5,910 22,450 7,704 5,910 30,154 36,064 11,022 35 2011 A 82,834 303 Second St., San Francisco, CA (10) 63,550 154,153 99,670 63,550 253,823 317,373 96,466 35 2010 A 784,658 333 Brannan St., San Francisco, CA 18,645 — 80,788 18,645 80,787 99,433 11,221 35 2016 C 185,602 345 Brannan St., San Francisco, CA 29,405 113,179 752 29,403 113,933 143,336 6,967 35 2018 A 110,050 350 Mission St., San Francisco, CA 52,815 — 213,312 52,815 213,312 266,127 31,186 35 2016 C 455,340 360 Third St., San Francisco, CA — 88,235 121,629 28,504 181,360 209,864 53,833 35 2011 A 429,796 1800 Owens St., San Francisco, CA 95,388 — 437,715 95,388 437,715 533,103 20,951 35 2019 C 750,370 345 Oyster Point Blvd., South San Francisco, CA 13,745 18,575 — 13,745 18,576 32,320 1,723 35 2018 A 40,410 347 Oyster Point Blvd., South San Francisco, CA 14,071 18,289 44 14,071 18,333 32,404 1,701 35 2018 A 39,780 349 Oyster Point Blvd., South San Francisco, CA 23,112 22,601 324 23,112 22,925 46,037 2,968 35 2018 A 65,340 Kilroy Oyster Point, Phase I, South San Francisco, CA (11) — — 620 — 620 620 — 35 — — 505 Mathilda Ave., Sunnyvale, CA 37,843 1,163 50,450 37,943 51,513 89,456 9,267 35 2014 C 212,322 555 Mathilda Ave., Sunnyvale, CA 37,843 1,163 50,447 37,943 51,510 89,453 9,267 35 2014 C 212,322 599 Mathilda Ave., Sunnyvale, CA 13,538 12,559 63 13,538 12,622 26,160 4,559 35 2012 A 76,031 605 Mathilda Ave., Sunnyvale, CA 29,014 891 77,282 29,090 78,096 107,187 20,542 35 2014 C 162,785 601 108th Ave., Bellevue, WA — 214,095 40,300 — 254,395 254,395 88,958 35 2011 A 488,470 10900 NE 4th St., Bellevue, WA 25,080 150,877 45,984 25,080 196,861 221,941 62,594 35 2012 A 428,557 837 N. 34th St., Lake Union, WA — 37,404 6,293 — 43,697 43,697 12,787 35 2012 A 112,487 701 N. 34th St., Lake Union, WA — 48,027 8,545 — 56,572 56,572 18,277 35 2012 A 141,860 801 N. 34th St., Lake Union, WA — 58,537 20,661 — 79,198 79,198 20,013 35 2012 A 169,412 320 Westlake Ave. North, Lake Union, WA 87,589 (12) 14,710 82,018 14,453 14,710 96,471 111,181 23,304 35 2013 A 184,644 321 Terry Ave. North, Lake Union, WA (12) 10,430 60,003 10,366 10,430 70,369 80,799 18,091 35 2013 A 135,755 401 Terry Ave. North, Lake Union, WA 22,500 77,046 13 22,500 77,059 99,559 18,225 35 2014 A 140,605 333 Dexter Ave. North, South Lake Union, WA (13) — — 323,433 42,853 280,580 323,433 2,592 35 0 — KILROY REALTY CORPORATION AND KILROY REALTY, L.P. SCHEDULE III – REAL ESTATE AND ACCUMULATED DEPRECIATION – (Continued) December 31, 2020 Initial Cost Gross Amounts at Which Property Location Encumb- Land and improve- Buildings Costs Land and improve- Buildings Total Accumulated Depreci- ation Life (1) Date of Acquisition (A)/ Construction (C) (2) Rentable Square Feet (3) (unaudited) ($ in thousands) Residential Properties: 1550 N. El Centro Ave., Los Angeles, CA (4) (14) 16,970 39 136,137 16,970 136,176 153,146 17,894 35 2016 C — 3200 Paseo Village Way, Del Mar, CA (15) 106,419 — 272,457 106,419 272,457 378,876 7,316 35 2020 C — TOTAL OPERATING PROPERTIES 254,365 1,496,855 2,699,959 4,215,126 1,628,848 6,783,092 8,411,940 1,798,646 14,620,166 Undeveloped land and construction in progress — 874,773 — 903,333 874,773 903,333 1,778,106 — — TOTAL ALL PROPERTIES $ 254,365 (16) $ 2,371,628 $ 2,699,959 $ 5,118,459 $ 2,503,621 $ 7,686,425 $ 10,190,046 $ 1,798,646 14,620,166 ____________________ (1) The initial costs of buildings and improvements are depreciated over 35 years using a straight-line method of accounting; improvements capitalized subsequent to acquisition are depreciated over the shorter of the lease term or useful life, generally ranging from one (2) Represents our date of construction or acquisition, or of our predecessor, the Kilroy Group. (3) Represents the square footage of our stabilized portfolio. (4) These properties include the costs of a shared parking structure for a complex comprised of five office buildings and one residential tower. The costs of the parking structure are allocated amongst the six buildings. (5) These costs represent infrastructure costs incurred in 1989. During the third quarter of 2009, we exercised our option to terminate the ground lease at Kilroy Airport Center, Phase IV in Long Beach, California. We had previously leased this land, which is adjacent to our office properties at Kilroy Airport Center, Long Beach, for potential future development opportunities. (6) These properties secure a $166.8 million mortgage note. (7) These properties are currently in the tenant improvement phase of our in-process development projects and not yet in the stabilized portfolio. The estimated rentable square feet for these properties is 285,000 rentable square feet. (8) These properties are owned by Redwood City Partners LLC, a consolidated property partnership. (9) This property is owned by 100 First Street Member LLC, a consolidated property partnership. (10) This property is owned by 303 Second Street Member LLC, a consolidated property partnership. (11) Represents the tenant funded portion of base building improvements for a project under construction. (12) These properties secure a $87.6 million mortgage note. (13) This property is currently in the tenant improvement phase of our in-process development projects and not yet in the stabilized portfolio. The estimated rentable square feet for this property is 635,000 rentable square feet. (14) This property represents the 200-unit Columbia Square residential tower that was added to the stabilized portfolio in 2016. (15) This property represents the 608-unit One Paseo residential project that was added to the stabilized portfolio in 2020. (16) Represents gross aggregate principal amount before the effect of the deferred financing costs of $0.8 million as of December 31, 2020. As of December 31, 2020, the aggregate gross cost of property included above for federal income tax purposes approximated $8.6 billion. The following table reconciles the historical cost of total real estate held for investment from January 1, 2018 to December 31, 2020: Year Ended December 31, 2020 2019 2018 (1) (in thousands) Total real estate held for investment, beginning of year $ 9,628,773 $ 8,426,632 $ 7,417,777 Additions during period: Acquisitions — 460,512 581,671 Improvements, etc. 645,170 890,654 724,016 Total additions during period 645,170 1,351,166 1,305,687 Deductions during period: Cost of real estate sold (44,070) (120,788) (286,623) Other (39,827) (28,237) (10,209) Total deductions during period (83,897) (149,025) (296,832) Total real estate held for investment, end of year $ 10,190,046 $ 9,628,773 $ 8,426,632 ____________________ (1) Amounts presented in Improvements, etc. and Other have been revised for the year ended December 31, 2018 to conform to the current year presentation with amounts transferred from undeveloped land and construction in progress to land and improvements and buildings and improvements presented on a net basis, which did not have any impact on total real estate held for investment at December 31, 2018. The following table reconciles the accumulated depreciation from January 1, 2018 to December 31, 2020: Year Ended December 31, 2020 2019 2018 (in thousands) Accumulated depreciation, beginning of year $ 1,561,361 $ 1,391,368 $ 1,264,162 Additions during period: Depreciation of real estate 244,815 211,893 198,578 Total additions during period 244,815 211,893 198,578 Deductions during period: Write-offs due to sale (6,401) (41,655) (71,372) Other (1,129) (245) — Total deductions during period (7,530) (41,900) (71,372) Accumulated depreciation, end of year $ 1,798,646 $ 1,561,361 $ 1,391,368

Basis of Presentation and Sig_2

Basis of Presentation and Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Basis of Presentation and Significant Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The consolidated financial statements of the Company include the consolidated financial position and results of operations of the Company, the Operating Partnership, 303 Second LLC, 100 First LLC, Redwood LLC and all of our wholly-owned and controlled subsidiaries. The consolidated financial statements of the Operating Partnership include the consolidated financial position and results of operations of the Operating Partnership, 303 Second LLC, 100 First LLC, Redwood LLC and all of our wholly-owned and controlled subsidiaries. All intercompany balances and transactions have been eliminated in the consolidated financial statements.
Partially Owned Entities and Variable Interest Entities	Our accounting policy is to consolidate entities in which we have a controlling financial interest and significant decision making control over the entity's operations. In determining whether we have a controlling financial interest in a partially owned entity and the requirement to consolidate the accounts of that entity, we consider factors such as ownership interest, board representation, management representation, size of our investment (including loans), authority to control decisions, and contractual and substantive participating rights of the members. In addition to evaluating control rights, we consolidate entities in which the other members have no substantive kick-out rights to remove the Company as the managing member. Entities in which the equity investors do not have sufficient equity at risk to finance their endeavors without additional financial support or the holders of the equity investment at risk do not have a controlling financial interest are VIEs. We evaluate whether an entity is a VIE and whether we are the primary beneficiary. We are deemed to be the primary beneficiary of a VIE when we have the power to direct the activities of the VIE that most significantly impact the VIEs’ economic performance and the obligation to absorb losses or receive benefits that could potentially be significant to the VIE.
Accounting Pronouncement Adopted and Accounting Standards Issued But Not Yet Effective	Accounting Pronouncements Adopted January 1, 2020 ASU No. 2016-13 “Financial Instruments - Credit Losses (Topic 326)” Effective January 1, 2020, we adopted Financial Accounting Standards Board (“FASB”) FASB Accounting Standards Update (“ASU”) No. 2016-13 (“ASU 2016-13”), which amends the accounting for credit losses for certain financial instruments. Under the new guidance, an entity recognizes its estimate of expected credit losses as an allowance, which the FASB believes will result in more timely recognition of such losses. In November 2018, the FASB released ASU No. 2018-19 “Codification Improvements to Topic 326, Financial Instruments - Credit Losses.” This ASU clarifies that receivables arising from operating leases are not within the scope of Subtopic 326-20 “Financial Instruments – Credit Losses.” Instead, impairment of receivables arising from operating leases should be accounted for under Subtopic 842-30 “Leases – Lessor.” The adoption did not have a material impact on our consolidated financial statements or notes to our consolidated financial statements. ASU No. 2018-13 “Fair Value Measurement (Topic 820)” Effective January 1, 2020, we adopted FASB ASU No. 2018-13 (“ASU 2018-13”), which amends the disclosure requirements for fair value measurements. The amendments in ASU 2018-13 include new, modified and eliminated disclosure requirements and are the result of a broader disclosure project called FASB Concepts Statement, Conceptual Framework for Financial Reporting - Chapter 8: Notes to Financial Statements (the “Concepts Statement”), which the FASB finalized on August 28, 2018. The FASB used the guidance in the Concepts Statement to improve the effectiveness of Topic 820’s disclosure requirements. The adoption did not have a material impact on our consolidated financial statements or notes to our consolidated financial statements. ASU No. 2018-15 “Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40)” Effective January 1, 2020, we adopted FASB ASU No. 2018-15 (“ASU 2018-15”), which amends a customer’s accounting for implementation costs incurred in a cloud computing arrangement that is a service contract. ASU 2018-15 aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). The adoption did not have a material impact on our consolidated financial statements or notes to our consolidated financial statements. COVID-19 Lease Modification Accounting Relief The global impact of the COVID-19 pandemic continues to evolve rapidly. Both of the states where we own properties and/or have development projects (i.e., California and Washington), have reacted to the COVID-19 pandemic by instituting quarantines, restrictions on travel, “shelter in place” rules, restrictions on types of business that may continue to operate and/or restrictions on types of construction projects that may continue. These restrictions have impacted our business, as well as that of our tenants. Due to the business disruptions and challenges severely affecting the global economy caused by the COVID-19 pandemic, many lessors may be required to provide rent deferrals and other lease concessions to lessees. While the lease modification guidance in Accounting Standards Codification (“ASC”) Topic 842 (“Topic 842”) addresses routine changes to lease terms resulting from negotiations between the lessee and the lessor, this guidance did not contemplate concessions being so rapidly executed to address the sudden liquidity constraints of some lessees arising from the COVID-19 pandemic and restrictions intended to prevent its spread. In April 2020, the FASB staff issued a question and answer document (the “Lease Modification Q&A”) focused on the application of lease accounting guidance to lease concessions provided as a result of the COVID-19 pandemic. Under existing lease guidance, the Company would have to determine, on a lease by lease basis, if a lease concession was the result of a new arrangement reached with the tenant (treated within the lease modification accounting framework) or if a lease concession was under the enforceable rights and obligations within the existing lease agreement (precluded from applying the lease modification accounting framework). The Lease Modification Q&A allows the Company, if certain criteria have been met, to bypass the lease by lease analysis, and instead elect to either apply the lease modification accounting framework or not, with such election applied consistently to leases
Revenue Recognition, Base Rent, Additional Rent - Reimbursements from Tenants, Other Property Income, Uncollectible Lease Receivables and Allowance for Tenant and Deferred Rent Receivables	Revenue Recognition Rental revenue for office, life science and retail operating properties is our principal source of revenue. We recognize revenue from base rent, additional rent (which consists of amounts due from tenants for common area maintenance, real estate taxes, and other recoverable costs), parking and other lease-related revenue once all of the following criteria are met: (i) the agreement has been fully executed and delivered, (ii) services have been rendered, (iii) the amount is fixed or determinable and (iv) payment has been received or the collectability of the amount due is probable. Lease termination fees are amortized over the remaining lease term, if applicable. If there is no remaining lease term, they are recognized when received and realized. Minimum annual rental revenues are recognized in rental revenues on a straight-line basis over the non-cancellable term of the related lease. Base Rent The timing of when we commence rental revenue recognition for office, life science and retail properties depends largely on our conclusion as to whether the Company or the tenant is the owner for accounting purposes of tenant improvements at the leased property. When we conclude that we are the owner of tenant improvements for accounting purposes, we record the cost to construct the tenant improvements as an asset and commence rental revenue recognition when the tenant takes possession of or controls the finished space, which is generally when tenant improvements being recorded as our assets are substantially complete. In certain instances, when we conclude that the tenant is the owner of certain tenant improvements for accounting purposes, rental revenue recognition begins when the tenant takes possession or controls the physical use of the leased space, which may occur in phases or for an entire building or project. The determination of who owns the tenant improvements is made on a lease-by-lease basis and has a significant effect on the timing of commencement of revenue recognition. When we conclude that the Company is the owner of tenant improvements for accounting purposes, we record the cost to construct the tenant improvements, including costs paid for or reimbursed by the tenants, as a capital asset. For these tenant-funded tenant improvements, we record the amount funded by or reimbursed by tenants as deferred revenue, which is amortized and recognized as rental income on a straight-line basis over the term of the related lease. When we conclude that the tenant is the owner of certain tenant improvements for accounting purposes, we record our contribution towards those tenant-owned improvements as a lease incentive, which is included in deferred leasing costs and acquisition-related intangible assets, net on our consolidated balance sheets and amortized as a reduction to rental revenue on a straight-line basis over the term of the related lease. For residential properties, we commence revenue recognition upon lease commencement. Residential rental revenue is recognized on a straight-line basis over the term of the related lease, net of any concessions. Additional Rent - Reimbursements from Tenants Additional rent, consisting of amounts due from tenants for common area maintenance, real estate taxes and other recoverable costs, are recognized in rental income in the period the recoverable costs are incurred. Prior to the adoption of Topic 842 on January 1, 2019, such amounts were recognized in revenue as tenant reimbursements. Additional rent where we pay the associated costs directly to third-party vendors and are reimbursed by our tenants are recognized and recorded on a gross basis, with the corresponding expense recognized in property expenses or real estate taxes. Prior to the adoption of Topic 842, recoverable costs were generally recognized and recorded on a gross basis when we were the primary obligor with respect to purchasing goods and services from third-party suppliers, had discretion in selecting the supplier, and had credit risk. Other Property Income Other property income primarily includes amounts recorded in connection with transient daily parking, tenant bankruptcy settlement payments, broken deal income and property damage settlement related payments. Other property income also includes miscellaneous income from tenants, restoration fees and fees for late rental payments. Amounts recorded within other property income fall within the scope of Topic 606 and are recognized as revenue at the point in time when control of the goods or services transfers to the customer and our performance obligation is satisfied. Prior to the adoption of Topic 842 on January 1, 2019, other property income primarily included amounts recorded in connection with lease terminations, tenant bankruptcy settlement payments, broken deal income and property damage settlement payments. Uncollectible Lease Receivables and Allowances for Tenant and Deferred Rent Receivables We carry our current and deferred rent receivables net of allowances for amounts that may not be collected. Prior to the adoption of Topic 842 on January 1, 2019, the allowances were increased or decreased through provision for bad debts on our consolidated statements of operations. Upon the adoption of Topic 842 on January 1, 2019, the allowances are increased or decreased through rental income, and our determination of the adequacy of the Company’s allowances for tenant receivables includes a binary assessment of whether or not substantially all of the amounts due under a tenant’s lease agreement are probable of collection. Such assessment involves using a methodology that incorporates a specific identification analysis and an aging analysis and considers the current economic and business environment. This determination requires significant judgment and estimates about matters that are uncertain at the time the estimates are made, including the creditworthiness of specific tenants, specific industry trends and conditions, and general economic trends and conditions. For leases that are deemed probable of collection, revenue continues to be recorded on a straight-line basis over the lease term. For leases that are deemed not probable of collection, revenue is recorded as the lesser of (i) the amount which would be recognized on a straight-line basis or (ii) cash that has been received from the tenant, including deferred revenue, with any tenant and deferred rent receivable balances charged as a direct write-off against rental income in the period of the change in the collectability determination. For tenant and deferred rent receivables associated with leases whose rents are deemed probable of collection under Topic 842, we may record an allowance under other authoritative GAAP using a methodology that incorporates a specific identification analysis and an aging analysis and considers the current economic and business environment. This determination requires significant judgment and estimates about matters that are uncertain at the time the estimates are made, including the creditworthiness of specific tenants, specific industry trends and conditions, and general economic trends and conditions. Tenant and deferred rent receivables deemed probable of collection are carried net of allowances for uncollectible accounts, with increases or decreases in the allowances recorded through rental income on our consolidated statements of operations. Prior to the adoption of Topic 842 on January 1, 2019, the allowances were increased or decreased through provision for bad debts on our consolidated statements of operations. Current tenant receivables consist primarily of amounts due for contractual lease payments and reimbursements of common area maintenance expenses, property taxes, and other costs recoverable from tenants. With respect to the allowance for uncollectible tenant receivables, the specific identification methodology analysis relies on factors such as the age and nature of the receivables, the payment history and financial condition of the tenant, our assessment of the tenant’s ability to meet its lease obligations, and the status of negotiations of any disputes with the tenant. Deferred rent receivables represent the amount by which the cumulative straight-line rental revenue recorded to date exceeds cash rents billed to date under the lease agreement. With respect to the allowance for deferred rent receivables, given the longer-term nature of these receivables, the specific identification methodology analysis evaluates each of our significant tenants and any tenants on our internal watchlist and relies on factors such as each tenant’s financial condition and its ability to meet its lease obligations. We evaluate our reserve levels quarterly based on changes in the financial condition of tenants and our assessment of the tenant’s ability to meet its lease obligations, overall economic conditions, and the current business environment.
Acquisitions	Acquisitions Acquisitions of operating properties and development and redevelopment opportunities generally do not meet the definition of a business and are accounted for as asset acquisitions, as substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or a group of similar identifiable assets. For these asset acquisitions, we record the acquired tangible and intangible assets and assumed liabilities based on each asset’s and liability’s relative fair value at the acquisition date of the total purchase price plus any capitalized acquisition costs. We record the acquired tangible and intangible assets and assumed liabilities of acquisitions of operating properties and development and redevelopment opportunities that meet the accounting criteria to be accounted for as business combinations at fair value at the acquisition date. Transaction costs associated with asset acquisitions, including costs incurred during negotiation, are capitalized in addition to the purchase price of the acquisition. The acquired assets and assumed liabilities for an acquisition generally include but are not limited to (i) land and improvements, buildings and improvements, undeveloped land and construction in progress and (ii) identified tangible and intangible assets and liabilities associated with in-place leases, including tenant improvements, leasing costs, value of above-market and below-market operating leases and ground leases, acquired in-place lease values and tenant relationships, if any. Any debt assumed and equity (including common units of the Operating Partnership) issued in connection with a property acquisition is recorded at fair value on the date of acquisition. The fair value of land and improvements is derived from comparable sales of land and improvements within the same submarket and/or region. The fair value of buildings and improvements, tenant improvements and leasing costs considers the value of the property as if it was vacant as well as current replacement costs and other relevant market rate information. The fair value of the above-market or below-market component of an acquired in-place operating lease is based upon the present value (calculated using a market discount rate) of the difference between (i) the contractual rents to be paid pursuant to the lease over its remaining non-cancellable lease term and (ii) our estimate of the rents that would be paid using fair market rental rates and rent escalations at the date of acquisition measured over the remaining non-cancellable term of the lease for above-market operating leases and the initial non-cancellable term plus the term of any below-market fixed rate renewal options, if applicable, for below-market operating leases. Our below-market operating leases generally do not include fixed rate or below-market renewal options. The amounts recorded for above-market operating leases are included in deferred leasing costs and acquisition-related intangible assets, net on the balance sheet and are amortized on a straight-line basis as a reduction of rental income over the remaining term of the applicable leases. The amounts recorded for below-market operating leases are included in deferred revenue and acquisition-related intangible liabilities, net on the balance sheet and are amortized on a straight-line basis as an increase to rental income over the remaining term of the applicable leases plus the term of any below-market fixed rate renewal options, if applicable. The amortization of a below-market ground lease obligation is recorded as an increase to ground lease expense in the consolidated statements of operations for the periods presented. The amortization of an above-market ground lease obligation is recorded as a decrease to ground lease expense in the consolidated statements of operations for the periods presented. The fair value of acquired in-place leases is derived based on our assessment of lost revenue and costs incurred for the period required to lease the “assumed vacant” property to the occupancy level when purchased. The amount recorded for acquired in-place leases is included in deferred leasing costs and acquisition-related intangible assets, net on the balance sheet and amortized as an increase to depreciation and amortization expense over the remaining term of the applicable leases. Fully amortized intangible assets are written off each quarter.
Operating Properties and Cost Capitalization and Depreciation and Amortization of Buildings and Improvements	Operating Properties Operating properties are generally carried at historical cost less accumulated depreciation. Properties held for sale are reported at the lower of the carrying value or the fair value less estimated cost to sell. The cost of operating properties includes the purchase price or development costs of the properties. Costs incurred for the renovation and betterment of the operating properties are capitalized to our investment in that property. Maintenance and repairs are charged to expense as incurred. When evaluating properties to be held and used for potential impairment, we first evaluate whether there are any indicators of impairment for any of our properties. If any impairment indicators are present for a specific property, we then evaluate the regional market conditions that could reasonably affect the property. If there are negative changes and trends in that regional market, we then perform an undiscounted cash flow analysis and compare the net carrying amount of the property to the property’s estimated undiscounted future cash flow over the anticipated holding period. If the estimated undiscounted future cash flow is less than the net carrying amount of the property, we perform an impairment loss calculation to determine if the fair value of the property is less than the net carrying value of the property. Our impairment loss calculation compares the net carrying amount of the property to the property’s estimated fair value, which may be based on estimated discounted future cash flow calculations or third-party valuations or appraisals. We would recognize an impairment loss if the property's net carrying amount exceeds the property's estimated fair value. If we were to recognize an impairment loss, the estimated fair value of the property becomes its new cost basis. For a depreciable long-lived asset, the new cost basis would be depreciated (amortized) over the remaining useful life of that asset. Cost Capitalization All costs clearly associated with the development, redevelopment and construction of a property are capitalized as project costs, including internal compensation costs. In addition, the following costs are capitalized as project costs during periods in which activities necessary to prepare development and redevelopment properties for their intended use are in progress: pre-construction costs essential to the development of the property, interest, real estate taxes and insurance. • For office, life science and retail development and redevelopment properties that are pre-leased, we cease capitalization when revenue recognition commences, which is upon substantial completion of tenant improvements deemed to be the Company’s asset for accounting purposes. • For office, life science and retail development and redevelopment properties that are not pre-leased, we may not immediately build out the tenant improvements. Therefore, we cease capitalization when revenue recognition commences upon substantial completion of the tenant improvements deemed to be the Company's asset for accounting purposes, but in any event, no later than one year after the cessation of major construction activities. We also cease capitalization on a development or redevelopment property when activities necessary to prepare the property for its intended use have been suspended. • For office, life science and retail development or redevelopment properties with multiple tenants and phased leasing, we cease capitalization and begin depreciation on the portion of the development or redevelopment property for which revenue recognition has commenced. • For residential development properties, we cease capitalization when the property is substantially complete and available for occupancy. Once major base building construction activities have ceased and the development or redevelopment property or phases of the development or redevelopment project is placed in service, which may occur in phases or for an entire building or project, the costs capitalized to construction in progress are transferred to land and improvements, buildings and improvements, and deferred leasing costs on our consolidated balance sheets as the historical cost of the property.
Real Estate Assets Held for Sale, Dispositions and Discontinued Operations	Real Estate Assets Held for Sale, Dispositions and Discontinued Operations A real estate asset is classified as held for sale when certain criteria are met, including but not limited to the availability of the asset for immediate sale, the existence of an active program to locate a buyer and the probable sale or transfer of the asset within one year. If such criteria are met, we present the applicable assets and liabilities related to the real estate asset, if material, separately on the balance sheet as held for sale and we would cease to record depreciation and amortization expense. Real estate assets held for sale are reported at the lower of their carrying value or their estimated fair value less the estimated costs to sell. As of December 31, 2020 and 2019, we did not have any properties classified as held for sale. Property disposals representing a strategic shift that have (or will have) a major effect on the Company’s operations and financial results, such as a major line of business, a major geographical area or a major equity investment, are required to be presented as discontinued operations. If we were to determine that a property disposition represents a strategic shift, the revenues, expenses and net gain (loss) on dispositions of the property would be recorded in discontinued operations for all periods presented through the date of the applicable disposition. The operations of the properties sold during the years ended December 31, 2020, 2019 and 2018 are presented in continuing operations as they did not represent a strategic shift in the Company’s operations and financial results.
Cash and Cash Equivalents	Cash and Cash EquivalentsWe consider all highly-liquid investments with original maturities of three months or less to be cash equivalents
Restricted Cash	Restricted CashRestricted cash consists of cash proceeds from dispositions that are temporarily held at qualified intermediaries for purposes of facilitating potential Section 1031 Exchanges and cash held in escrow related to acquisition and disposition holdbacks. Restricted cash also includes cash held as collateral to provide credit enhancement for the Operating Partnership’s mortgage debt, including cash reserves for capital expenditures, tenant improvements and property taxes.
Marketable Securities	Marketable securities reported in our consolidated balance sheets represent the assets held in connection with the Kilroy Realty Corporation 2007 Deferred Compensation Plan (the “Deferred Compensation Plan”) (see Note 16 “Employee Benefit Plans” for additional information). The Deferred Compensation Plan assets are held in a limited rabbi trust and invested in various mutual and money market funds. As a result, the marketable securities are treated as trading securities for financial reporting purposes and are adjusted to fair value at the end of each accounting period, with the corresponding gains and losses recorded in interest income and other net investment gains (losses).
Deferred Compensation Plan	At the time eligible management employees (“Participants”) defer compensation or earn mandatory Company contributions, or if we were to make a discretionary contribution, we record compensation cost and a corresponding deferred compensation plan liability, which is included in accounts payable, accrued expenses, and other liabilities on our consolidated balance sheets. This liability is adjusted to fair value at the end of each accounting period based on the performance of the benchmark funds selected by each Participant, and the impact of adjusting the liability to fair value is recorded as an increase or decrease to compensation cost. The impact of adjusting the deferred compensation plan liability to fair value and the changes in the value of the marketable securities held in connection with the Deferred Compensation Plan generally offset and therefore do not significantly impact net income.
Deferred Leasing Costs	Deferred Leasing Costs Costs incurred in connection with successful property leasing are capitalized as deferred leasing costs and classified as investing activities in the statement of cash flows. Under Topic 842, initial direct costs include only those costs that are incremental to the arrangement and would not have been incurred if the lease had not been obtained. As a result, subsequent to the adoption of Topic 842 on January 1, 2019, deferred leasing costs consist of leasing commissions paid to external third party brokers and lease incentives, and the Company no longer capitalizes internal leasing costs and third-party legal leasing costs. Prior to the adoption of Topic 842, deferred leasing costs consisted primarily of leasing commissions, lease incentives, legal costs and certain internal payroll costs. Deferred leasing costs are amortized using the straight-line method of accounting over the lives of the leases which generally range from one
Deferred Financing Costs, and Debt Discounts and Premiums	Deferred Financing Costs Financing costs related to the origination or assumption of long-term debt are deferred and generally amortized using the straight-line method of accounting, which approximates the effective interest method, over the contractual terms of the applicable financings. Fully amortized deferred financing costs are written off when the corresponding financing is repaid. Debt Discounts and Premiums
Noncontrolling Interests and Common Partnership Interests	Noncontrolling Interests - Common Units of the Operating Partnership in the Company's Consolidated Financial Statements Common units of the Operating Partnership within noncontrolling interests in the Company’s consolidated financial statements represent the common limited partnership interests in the Operating Partnership not held by the Company (“noncontrolling common units”). Noncontrolling common units are presented in the equity section of the Company’s consolidated balance sheets and are reported at their proportionate share of the net assets of the Operating Partnership. Noncontrolling interests with redemption provisions that permit the issuer to settle in either cash or shares of common stock must be further evaluated to determine whether equity or temporary equity classification on the balance sheet is appropriate. Since the common units contain such a provision, we evaluated the accounting guidance and determined that the common units qualify for equity presentation in the Company’s consolidated financial statements. Net income attributable to noncontrolling common units is allocated based on their relative ownership percentage of the Operating Partnership during the reported period. The noncontrolling interest ownership percentage is determined by dividing the number of noncontrolling common units by the total number of common units outstanding. The issuance or redemption of additional shares of common stock or common units results in changes to the noncontrolling interest percentage as well as the total net assets of the Company. As a result, all equity transactions result in an allocation between equity and the noncontrolling interest in the Company’s consolidated balance sheets and statements of equity to account for the changes in the noncontrolling interest ownership percentage as well as the change in total net assets of the Company. Noncontrolling Interests in Consolidated Property Partnerships Noncontrolling interests in consolidated property partnerships represent the equity interests held by unrelated third parties in our three consolidated property partnerships (see Note 11 “Noncontrolling Interests on the Company’s Consolidated Financial Statements” and see Note 12 “Noncontrolling Interests on the Operating Partnership’s Consolidated Financial Statements”). Noncontrolling interests in consolidated property partnerships are not redeemable and are presented as permanent equity in the Company's consolidated balance sheets. We account for the noncontrolling interests in consolidated property partnerships using the hypothetical liquidation at book value (“HLBV”) method to attribute the earnings or losses of the consolidated property partnerships between the controlling and noncontrolling interests. Under the HLBV method, the amounts reported as noncontrolling interests in consolidated property partnerships in the consolidated balance sheets represent the amounts the noncontrolling interests would hypothetically receive at each balance sheet reporting date under the liquidation provisions of the governing agreements assuming the net assets of the consolidated property partnerships were liquidated at recorded amounts and distributed between the controlling and noncontrolling interests in accordance with the governing documents. The net income attributable to noncontrolling interests in consolidated property partnerships in the consolidated statements of operations is associated with the increase or decrease in the noncontrolling interest holders’ contractual claims on the respective entities’ balance sheets assuming a hypothetical liquidation at the end of that reporting period when compared with their claims on the respective entities’ balance sheets assuming a hypothetical liquidation at the beginning of that reporting period, after removing any contributions or distributions. Common Partnership Interests on the Operating Partnership’s Consolidated Balance Sheets The common units held by the Company and the noncontrolling common units held by the common limited partners are both presented in the permanent equity section of the Operating Partnership’s consolidated balance sheets in partners’ capital. The redemption rights of the noncontrolling common units permit us to settle the redemption obligation in either cash or shares of the Company’s common stock at our option (see Note 11 “Noncontrolling Interests on the Company’s Consolidated Financial Statements” for additional information). Noncontrolling Interests on the Operating Partnership’s Consolidated Financial Statements
Equity Offerings	Equity Offerings Underwriting commissions and offering costs incurred in connection with common equity offerings and our at-the-market stock offering program (see Note 13 “Stockholders’ Equity of the Company”) are reflected as a reduction of additional paid-in capital. Issuance costs incurred in connection with preferred equity offerings are reflected as a reduction of the carrying value of the preferred equity. Sales of our common stock under forward equity sale agreements (such as those under the forward equity offering entered into in February 2020 and those under the 2018 At-The-Market Program, as discussed in Note 13 “Stockholders’ Equity of the Company”) meet the derivatives and hedging guidance scope exception to be accounted for as equity instruments based on the following assessment: (i) none of the agreements’ exercise contingencies were based on observable markets or indices besides those related to the market for our own stock price and operations; and (ii) none of the settlement provisions precluded the agreements from being indexed to our own stock.
Share-based Incentive Compensation Accounting	Share-based Incentive Compensation Accounting Compensation cost for all share-based awards, including options, requires measurement at estimated fair value on the grant date. Compensation cost is recognized on a straight-line basis over the service vesting period, which represents the requisite service period. The grant date fair value of market measure-based share-based compensation plans are calculated using a Monte Carlo simulation pricing model. The grant date fair value of stock option grants is calculated using the Black-Scholes valuation model. Equity awards settled in cash are valued at the fair value of our common stock on the period end date through the settlement date. Equity awards settled in cash are remeasured at each reporting period and are recognized as a liability in the consolidated balance sheet during the vesting period until settlement. Forfeitures of all share-based awards are recognized when they occur. For share-based awards in which the performance period precedes the grant date, we recognize compensation cost over the requisite service period, which includes both the performance and service vesting periods, using the accelerated attribution expense method. The requisite service period begins on the date the Executive Compensation Committee authorizes the award and adopts any relevant performance measures. For share-based awards with performance-based measures, the total estimated compensation cost is based on our most recent estimate of the probable achievement of the pre-established specific corporate performance measures. These estimates are based on actual results and our latest internal forecasts for each performance measure. For share-based awards with market measures, the total estimated compensation cost is based on the fair value of the award at the grant date. For share-based awards with performance-based measures and market measures, the total estimated compensation cost is based on the fair value per share at the grant date multiplied by our most recent estimate of the number of shares to be earned based on actual results and the probable achievement of the pre-established corporate performance measures based on our latest internal forecasts. In accordance with the provisions of our share-based incentive compensation plan, we accept the return of shares of Company common stock, at the current quoted market price, from employees to satisfy minimum statutory tax-withholding requirements related to shares that vested during the period.
Basic and Diluted Net Income Available to Common Stockholders per Share	Basic and Diluted Net Income Available to Common Stockholders per Share Basic net income available to common stockholders per share is computed by dividing net income available to common stockholders, after preferred distributions and the allocation of income to participating securities, by the weighted-average number of shares of common stock outstanding for the period. Diluted net income available to common stockholders per share is computed by dividing net income available for common stockholders, after preferred distributions and the allocation of income to participating securities, by the sum of the weighted-average number of shares of common stock outstanding for the period plus the assumed exercise of all dilutive securities. The impact of the outstanding common units is considered in the calculation of diluted net income available to common stockholders per share. The common units are not reflected in the diluted net income available to common stockholders per share calculation because the exchange of common units into common stock is on a one for one basis, and the common units are allocated net income on a per share basis equal to the common stock (see Note 21 “Net Income Available to Common Stockholders Per Share of the Company”). Accordingly, any exchange would not have any effect on diluted net income (loss) available to common stockholders per share. Nonvested share-based payment awards (including nonvested restricted stock units (“RSUs”), vested market-measure RSUs and vested dividend equivalents issued to holders of RSUs) containing nonforfeitable rights to dividends or dividend equivalents are accounted for as participating securities and included in the computation of basic and diluted net income available to common stockholders per share pursuant to the two-class method. The dilutive effect of shares issuable under executed forward equity sale agreements, if any, and stock options are reflected in the weighted average diluted outstanding shares calculation by application of the treasury stock method. The dilutive effect of the outstanding nonvested shares of common stock (“nonvested shares”) and RSUs that have not yet been granted but are contingently issuable under the share-based compensation programs is reflected in the weighted average diluted shares calculation by application of the treasury stock method at the beginning of the quarterly period in which all necessary conditions have been satisfied. Basic and Diluted Net Income Available to Common Unitholders per Unit Basic net income available to common unitholders per unit is computed by dividing net income available to common unitholders, after preferred distributions and the allocation of income to participating securities, by the weighted-average number of vested common units outstanding for the period. Diluted net income available to common unitholders per unit is computed by dividing net income available to common unitholders, after preferred distributions and the allocation of income to participating securities, by the sum of the weighted-average number of common units outstanding for the period plus the assumed exercise of all dilutive securities.
Fair Value Measurements	Fair Value Measurements The fair values of our financial assets and liabilities are disclosed in Note 19, “Fair Value Measurements and Disclosures,” to our consolidated financial statements. The only financial assets recorded at fair value on a recurring basis in our consolidated financial statements are our marketable securities. We elected not to apply the fair value option for any of our eligible financial instruments or other items. We determine the estimated fair value of financial assets and liabilities utilizing a hierarchy of valuation techniques based on whether the inputs to a fair value measurement are considered to be observable or unobservable in a marketplace. Observable inputs reflect market data obtained from independent sources, while unobservable inputs reflect our market assumptions. This hierarchy requires the use of observable market data when available. The following is the fair value hierarchy: • Level 1 – quoted prices for identical instruments in active markets; • Level 2 – quoted prices for similar instruments in active markets; quoted prices for identical or similar instruments in markets that are not active and model-derived valuations in which significant inputs and significant value drivers are observable in active markets; and • Level 3 – fair value measurements derived from valuation techniques in which one or more significant inputs or significant value drivers are unobservable. We determine the fair value for the marketable securities using quoted prices in active markets for identical assets. Our other financial instruments, which are only disclosed at fair value, are comprised of secured debt, unsecured senior notes, unsecured line of credit and unsecured term loan facility. We generally determine the fair value of our secured debt, unsecured debt, unsecured line of credit and unsecured term loan facility, prior to its repayment in August 2020, by performing discounted cash flow analyses using an appropriate market discount rate. We calculate the market rate by obtaining period-end treasury rates for maturities that correspond to the maturities of our fixed-rate debt and then adding an appropriate credit spread based on information obtained from third-party financial institutions. These credit spreads take into account factors, including but not limited to, our credit profile, the tenure of the debt, amortization period, whether the debt is secured or unsecured, and the loan-to-value ratio of the debt to the collateral. These calculations are significantly affected by the assumptions used, including the discount rate, credit spreads and estimates of future cash flow. We calculate the market rate of our unsecured line of credit and unsecured term loan facility by obtaining the period-end London Interbank Offered Rate (“LIBOR”) and then adding an appropriate credit spread based on our credit ratings, and the amended terms of our unsecured line of credit and unsecured term loan facility agreement. We determine the fair value of each of our publicly traded unsecured senior notes based on their quoted trading price at the end of the reporting period, if such prices are available. Carrying amounts of our cash and cash equivalents, restricted cash and accounts payable approximate fair value due to their short-term maturities.
Income Taxes	Income Taxes We have elected to be taxed as a REIT under Sections 856 through 860 of the Code. To qualify as a REIT, we must distribute annually at least 90% of our adjusted taxable income, as defined in the Code, to our stockholders and satisfy certain other organizational and operating requirements. We generally will not be subject to federal income taxes if we distribute 100% of our taxable income for each year to our stockholders. If we fail to qualify as a REIT in any taxable year, we will be subject to federal income taxes on our taxable income at regular corporate rates and we may not be able to qualify as a REIT for four subsequent taxable years. Even if we qualify for taxation as a REIT, we may be subject to certain state and local taxes on our income and property and to federal income taxes and excise taxes on our undistributed taxable income. We believe that we have met all of the REIT distribution and technical requirements for the years ended December 31, 2020, 2019 and 2018, and we were not subject to any federal income taxes (see Note 25 “Tax Treatment of Distributions” for additional information). We intend to continue to adhere to these requirements and maintain the Company’s REIT status. Accordingly, no provision for income taxes has been made in the accompanying financial statements. In addition, any taxable income from our taxable REIT subsidiaries, which were formed in 2002, 2018, 2019 and 2020, are subject to federal, state, and local income taxes. For the years ended December 31, 2020, 2019 and 2018 the taxable REIT subsidiaries had de minimis taxable income.
Uncertain Tax Positions	Uncertain Tax Positions We include favorable tax positions in the calculation of tax liabilities if it is more likely than not that our adopted tax position will prevail if challenged by tax authorities.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reported periods. Actual results could differ from those estimates.
Segments	SegmentsWe currently operate in one operating segment, our office and life science properties segment.
Concentration of Credit Risk	Concentration of Credit RiskAll of our properties and development and redevelopment projects are owned and all of our business is currently conducted in the state of California with the exception of the ownership and operation of eight office properties, one development project in the tenant improvement phase and one future development project located in the state of Washington. The ability of tenants to honor the terms of their leases is dependent upon the economic, regulatory, and social factors affecting the communities in which our tenants operate.

Organization and Ownership (Tab

Organization and Ownership (Tables)	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of real estate properties	Our stabilized portfolio of operating properties was comprised of the following properties at December 31, 2020: Number of Rentable Number of Percentage Occupied (unaudited) (1) Percentage Leased Stabilized Office Properties (2) 117 14,620,166 447 91.2 % 94.3 % _______________________ (1) Represents physical and economic occupancy. (2) Includes stabilized life science and retail space. Number of Projects Number of Units 2020 Average Occupancy Stabilized Residential Properties 2 808 72.0 % Number of Estimated Rentable Square Feet (1) (unaudited) In-process development projects - tenant improvement 3 1,080,000 In-process development projects - under construction (2) 3 856,000 ____________________ (1) Estimated rentable square feet upon completion. (2) In addition to the estimated office and life science rentable square feet noted above, development projects under construction also include 193 residential units.

Basis of Presentation and Sig_3

Basis of Presentation and Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2020
Basis of Presentation and Significant Accounting Policies [Abstract]
Buildings, improvements, and tenant improvements depreciation	The costs of buildings and improvements and tenant improvements are depreciated using the straight-line method of accounting over the estimated useful lives set forth in the table below. Depreciation expense for buildings and improvements for the three years ended December 31, 2020, 2019, and 2018 was $244.8 million, $211.9 million, and $198.6 million, respectively. Asset Description Depreciable Lives Buildings and improvements 25 – 40 years Tenant improvements 1 – 20 years (1) ____________________

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2020
Asset Acquisitions [Abstract]
Schedule of Acquisitions	During the year ended December 31, 2019, we acquired the 19-building creative office campus listed below in one transaction from an unrelated third party. Property Date of Acquisition Number of Buildings Rentable Square Feet (unaudited) Purchase Price (in millions) (1) 2019 Acquisitions 3101-3243 La Cienega Boulevard, Culver City, CA (2) October 15, 2019 19 151,908 $ 186.0 ________________________ (1) Excludes acquisition-related costs. (2) The results of operations for the properties acquired during 2019 contributed $3.7 million to revenue and a net loss of $0.1 million for the year ended December 31, 2019 primarily due to a write-off of lease-related intangible assets as a result of an early lease termination during the year ended December 31, 2019. Project Date of Acquisition City/Submarket Purchase Price (in millions) 2019 Acquisitions 1335 Broadway & 901 Park Boulevard, San Diego, CA (1) August 19, 2019 East Village $ 40.0 Seattle CBD Project (2) December 12, 2019 Seattle CBD 133.0 Total 2019 Acquisitions $ 173.0 _______________________ (1) Excludes acquisition-related costs. In connection with this acquisition, we also recorded $4.0 million in accrued liabilities and environmental remediation liabilities at the date of acquisition, which are not included in the purchase price above. As of December 31, 2019, the purchase price and our current estimate of assumed liabilities are included in undeveloped land and construction in progress and the assumed liabilities are included in accounts payable, accrued expenses and other liabilities on the Company’s consolidated balance sheets.
Schedule of estimated fair values of the assets acquired and liabilities assumed	The related assets, liabilities and results of operations of the acquired properties are included in the consolidated financial statements as of the date of acquisition. The following table summarizes the estimated relative fair values of the assets and liabilities assumed at the acquisition date for our 2019 operating property acquisitions: Total 2019 Operating Property Acquisition (1) Assets Land and improvements $ 150,561 Buildings and improvements (2) 30,932 Deferred leasing costs and acquisition-related intangible assets (3) 12,063 Right of use ground lease asset (4) 13,334 Total assets acquired $ 206,890 Liabilities Acquisition-related intangible liabilities (5) $ 9,950 Ground lease liability (4) 10,940 Total liabilities assumed $ 20,890 Net assets and liabilities acquired $ 186,000 ________________________ (1) The purchase price of the acquisition completed during the year ended December 31, 2019 was less than 10% of the Company’s total assets as of December 31, 2018. (2) Represents buildings, building improvements and tenant improvements. (3) Represents in-place leases (approximately $9.2 million with a weighted average amortization period of 3.3 years) and leasing commissions (approximately $2.9 million with a weighted average amortization period of 3.5 years). (4) We evaluated the ground lease assumed in connection with the 2019 operating property acquisition and concluded it met the criteria to be classified as an operating lease. The discount rate used in determining the present value of the minimum future lease payments was 4.79%. The right of use asset ground lease asset is equal to the ground lease liability adjusted for above and below market intangibles and deferred leasing costs. Refer to Note 18 “Commitments and Contingencies” for further discussion of the Company's ground lease obligations. (5) Represents below-market leases (approximately $10.0 million with a weighted average amortization period of 3.5 years).

Dispositions (Tables)

Dispositions (Tables)	12 Months Ended
	Dec. 31, 2020
Discontinued Operations and Disposal Groups [Abstract]
Schedule operating properties and land dispositions	The following table summarizes the operating properties sold during the years ended December 31, 2020, 2019 and 2018: Location Month of Disposition Number of Buildings Rentable Sales Price (in millions) (1) 2020 Dispositions 331 Fairchild Drive, Mountain View, CA December 1 87,147 $ 75.9 Total 2020 Dispositions 1 87,147 $ 75.9 2019 Dispositions 2829 Townsgate Road, Thousand Oaks, CA May 1 84,098 $ 18.3 2211 Michelson Drive, Irvine, CA October 1 271,556 115.5 Total 2019 Dispositions 2 355,654 $ 133.8 2018 Dispositions 1310-1327 Chesapeake Terrace, Sunnyvale, CA November 4 266,982 $ 160.3 Plaza Yarrow Bay Properties (2) November 4 279,924 134.5 23925, 23975, & 24025 Park Sorrento, Calabasas, CA December 3 225,340 78.2 Total 2018 Dispositions 11 772,246 $ 373.0 ____________________ (1) Represents gross sales price before broker commissions and closing costs.

Deferred Leasing Costs and Ac_2

Deferred Leasing Costs and Acquisition-Related Intangible Assets and Liabilities, net (Tables)	12 Months Ended
	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Summary of identified deferred leasing costs and acquisition-related intangible assets	The following table summarizes our deferred leasing costs and acquisition-related intangible assets (acquired value of leasing costs, above-market operating leases, and in-place leases) and intangible liabilities (acquired value of below-market operating leases) as of December 31, 2020 and 2019: December 31, 2020 December 31, 2019 (in thousands) Deferred Leasing Costs and Acquisition-related Intangible Assets, net: Deferred leasing costs $ 300,556 $ 286,026 Accumulated amortization (104,277) (100,145) Deferred leasing costs, net 196,279 185,881 Above-market operating leases — 611 Accumulated amortization — (116) Above-market operating leases, net — 495 In-place leases 40,323 58,076 Accumulated amortization (25,653) (31,647) In-place leases, net 14,670 26,429 Total deferred leasing costs and acquisition-related intangible assets, net $ 210,949 $ 212,805 Acquisition-related Intangible Liabilities, net: (1) Below-market operating leases $ 26,405 $ 51,263 Accumulated amortization (13,060) (27,171) Below-market operating leases, net 13,345 24,092 Total acquisition-related intangible liabilities, net $ 13,345 $ 24,092 ____________________
Amortization for the period related to deferred leasing costs and acquisition-related intangibles	The following table sets forth amortization related to deferred leasing costs and acquisition-related intangibles for the years ended December 31, 2020, 2019 and 2018. Year Ended December 31, 2020 2019 2018 (in thousands) Deferred leasing costs (1) $ 33,624 $ 35,779 $ 34,341 Above-market operating leases (2) 495 192 444 In-place leases (1) 11,759 18,615 15,915 Below-market ground lease obligation (3) — — 8 Below-market operating leases (4) (10,748) (9,398) (10,192) Above-market ground lease obligation (3) — — (101) Total $ 35,130 $ 45,188 $ 40,415 ____________________ (1) The amortization of deferred leasing costs and in-place leases is recorded to depreciation and amortization expense and the amortization of lease incentives is recorded as a reduction to rental income in the consolidated statements of operations for the periods presented. (2) The amortization of above-market operating leases is recorded as a decrease to rental income in the consolidated statements of operations for the periods presented. (3) Upon adoption of Topic 842 on January 1, 2019 (refer to Note 2 “Basis of Presentation and Significant Accounting Policies”), we no longer separately recognize above or below-market ground lease obligations. Refer to Note 18 “Commitments and Contingencies” for further discussion of our ground lease obligations.
Estimated annual amortization related to deferred leasing costs and acquisition-related intangibles	The following table sets forth the estimated annual amortization expense related to deferred leasing costs and acquisition-related intangibles as of December 31, 2020 for future periods: Year Deferred Leasing Costs In-Place Leases Below-Market Operating Leases (1) (in thousands) 2021 $ 31,048 $ 6,531 $ (4,152) 2022 28,334 3,885 (3,167) 2023 24,470 1,534 (1,486) 2024 21,545 584 (812) 2025 19,726 473 (710) Thereafter 71,156 1,663 (3,018) Total $ 196,279 $ 14,670 $ (13,345) ____________________ (1) Represents estimated annual amortization related to below-market operating leases. Amounts will be recorded as an increase to rental income in the consolidated statements of operations.

Receivables (Tables)

Receivables (Tables)	12 Months Ended
	Dec. 31, 2020
Receivables [Abstract]
Current receivables, net	Current receivables, net is primarily comprised of contractual rents and other lease-related obligations due from tenants. The balance consisted of the following as of December 31, 2020 and 2019: December 31, 2020 December 31, 2019 (in thousands) Current receivables $ 13,806 $ 27,660 Allowance for uncollectible tenant receivables (1) (1,799) (1,171) Current receivables, net $ 12,007 $ 26,489 ____________________
Deferred rent receivables, net	Deferred rent receivables, net consisted of the following as of December 31, 2020 and 2019: December 31, 2020 December 31, 2019 (in thousands) Deferred rent receivables $ 387,462 $ 339,489 Allowance for deferred rent receivables (1) (804) (1,552) Deferred rent receivables, net $ 386,658 $ 337,937 ____________________

Prepaid Expenses and Other As_2

Prepaid Expenses and Other Assets, Net (Tables)	12 Months Ended
	Dec. 31, 2020
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid expenses and other assets, net	Prepaid expenses and other assets, net consisted of the following at December 31, 2020 and 2019: December 31, 2020 December 31, 2019 (in thousands) Furniture, fixtures and other long-lived assets, net $ 43,367 $ 35,286 Prepaid expenses 10,193 18,724 Notes receivable, net (1) — 1,651 Total prepaid expenses and other assets, net $ 53,560 $ 55,661 ____________________ (1) During the year ended December 31, 2020, the balance of the note receivable was written-off and the note receivable was placed on non-accrual status. We do not recognize interest income on non-accrual financing receivables. As of December 31, 2019, the note receivable was shown net of a valuation allowance of approximately $3.6 million.

Secured and Unsecured Debt of_3

Secured and Unsecured Debt of the Operating Partnership (Tables) - Kilroy Realty L.P. [Member]	12 Months Ended
	Dec. 31, 2020
Debt Instrument [Line Items]
Unsecured revolving credit facility	The following table summarizes the balance and terms of our unsecured revolving credit facility as of December 31, 2020 and 2019: December 31, 2020 December 31, 2019 (in thousands) Outstanding borrowings $ — $ 245,000 Remaining borrowing capacity 750,000 505,000 Total borrowing capacity (1) $ 750,000 $ 750,000 Interest rate (2) 1.14 % 2.76 % Facility fee-annual rate (3) 0.200% Maturity date July 2022 ____________________ (1) We may elect to borrow, subject to bank approval and obtaining commitments for any additional borrowing capacity, up to an additional $600.0 million under an accordion feature under the terms of the unsecured revolving credit facility and unsecured term loan facility. (2) Our unsecured revolving credit facility interest rate was calculated based on the contractual rate of LIBOR plus 1.000% as of December 31, 2020 and 2019. December 31, 2019 Outstanding borrowings $ 150,000 Remaining borrowing capacity — Total borrowing capacity (1) $ 150,000 Interest rate (2) 2.85 % Undrawn facility fee-annual rate 0.200% Maturity date July 2022 ____________________ (1) As of December 31, 2019, $0.7 million of unamortized deferred financing costs remained to be amortized through the maturity date of our unsecured term loan facility. (2) Our unsecured term loan facility interest rate was calculated based on the contractual rate of LIBOR plus 1.100% as of December 31, 2019.
Schedule of debt maturities	The following table summarizes the stated debt maturities and scheduled amortization payments as of December 31, 2020: Year (in thousands) 2021 $ 5,342 2022 5,554 2023 305,775 2024 431,006 2025 406,246 Thereafter 2,800,442 Total aggregate principal value (1) $ 3,954,365 ________________________ (1) Includes gross principal balance of outstanding debt before the effect of the following at December 31, 2020: $22.4 million of unamortized deferred financing costs for the unsecured senior notes and secured debt and $8.3 million of unamortized discounts for the unsecured senior notes.
Capitalized interest and loan fees	The following table sets forth gross interest expense, including debt discount/premium and deferred financing cost amortization, net of capitalized interest, for the years ended December 31, 2020, 2019 and 2018. The interest expense capitalized was recorded as a cost of development and increased the carrying value of undeveloped land and construction in progress. Year Ended December 31, 2020 2019 2018 (in thousands) Gross interest expense $ 150,325 $ 129,778 $ 117,789 Capitalized interest and deferred financing costs (79,553) (81,241) (68,068) Interest expense $ 70,772 $ 48,537 $ 49,721
Secured debt [Member]
Debt Instrument [Line Items]
Debt balance and significant terms	The following table sets forth the composition of our secured debt as of December 31, 2020 and 2019: Annual Stated Interest Rate (1) GAAP Effective Rate (1)(2) Maturity Date December 31, Type of Debt 2020 2019 (in thousands) Mortgage note payable 3.57% 3.57% December 2026 $ 166,776 $ 170,000 Mortgage note payable (3) 4.48% 4.48% July 2027 87,589 89,502 Total secured debt $ 254,365 $ 259,502 Unamortized Deferred Financing Costs (783) (909) Total secured debt, net $ 253,582 $ 258,593 ____________________ (1) All interest rates presented are fixed-rate interest rates. (2) Represents the effective interest rate including the amortization of initial issuance discounts/premiums excluding the amortization of deferred financing costs.
Unsecured senior notes [Member]
Debt Instrument [Line Items]
Debt balance and significant terms	The following table summarizes the balance and significant terms of the registered unsecured senior notes issued by the Operating Partnership and outstanding, including the issuances noted above, and including unamortized discounts of $8.3 million and $6.5 million and unamortized deferred financing costs of $21.6 million and $18.7 million as of December 31, 2020 and 2019, respectively: Net Carrying Amount Issuance date Maturity date Stated Effective interest rate (1) 2020 2019 (in thousands) 2.500% Unsecured Senior Notes (2) August 2020 November 2032 2.500% 2.560% $ 425,000 $ — Unamortized discount and deferred financing costs (6,332) — Net carrying amount $ 418,668 $ — 4.270% Unsecured Senior Notes (3) April 2020 January 2031 4.270% 4.270% $ 350,000 $ — Unamortized discount and deferred financing costs (1,825) — Net carrying amount $ 348,175 $ — 3.050% Unsecured Senior Notes (4) September 2019 February 2030 3.050% 3.064% $ 500,000 $ 500,000 Unamortized discount and deferred financing costs (5,399) (5,998) Net carrying amount $ 494,601 $ 494,002 4.750% Unsecured Senior Notes (5) November 2018 December 2028 4.750% 4.800% $ 400,000 $ 400,000 Unamortized discount and deferred financing costs (3,952) (4,446) Net carrying amount $ 396,048 $ 395,554 4.350% Unsecured Senior Notes (6) October 2018 October 2026 4.350% 4.350% $ 200,000 $ 200,000 Unamortized discount and deferred financing costs (1,012) (1,186) Net carrying amount $ 198,988 $ 198,814 4.300% Unsecured Senior Notes (6) July 2018 July 2026 4.300% 4.300% $ 50,000 $ 50,000 Unamortized discount and deferred financing costs (246) (290) Net carrying amount $ 49,754 $ 49,710 3.450% Unsecured Senior Notes (7) December 2017 December 2024 3.450% 3.470% $ 425,000 $ 425,000 Unamortized discount and deferred financing costs (2,321) (2,907) Net carrying amount $ 422,679 $ 422,093 3.450% Unsecured Senior Notes (8) February 2017 February 2029 3.450% 3.450% $ 75,000 $ 75,000 Unamortized discount and deferred financing costs (347) (390) Net carrying amount $ 74,653 $ 74,610 3.350% Unsecured Senior Notes (8) February 2017 February 2027 3.350% 3.350% $ 175,000 $ 175,000 Unamortized discount and deferred financing costs (709) (825) Net carrying amount $ 174,291 $ 174,175 4.375% Unsecured Senior Notes (9) September 2015 October 2025 4.375% 4.444% $ 400,000 $ 400,000 Unamortized discount and deferred financing costs (2,631) (3,185) Net carrying amount $ 397,369 $ 396,815 4.250% Unsecured Senior Notes (10) July 2014 August 2029 4.250% 4.350% $ 400,000 $ 400,000 Unamortized discount and deferred financing costs (4,567) (5,100) Net carrying amount $ 395,433 $ 394,900 3.800% Unsecured Senior Notes (11) January 2013 January 2023 3.800% 3.800% $ 300,000 $ 300,000 Unamortized discount and deferred financing costs (560) (834) Net carrying amount $ 299,440 $ 299,166 Total Unsecured Senior Notes, Net $ 3,670,099 $ 2,899,839 ____________________ (1) Represents the effective interest rate including the amortization of initial issuance discounts, excluding the amortization of deferred financing costs. (2) Interest on these notes is payable semi-annually in arrears on May 15 and November 15 of each year. (3) Interest on these notes is payable semi-annually in arrears on April 18 and October 18 of each year. (4) Interest on these notes is payable semi-annually in arrears on February 15th and August 15th of each year. (5) Interest on these notes is payable semi-annually in arrears on June 15th and December 15th of each year. (6) Interest on these notes is payable semi-annually in arrears on April 18th and October 18th of each year. (7) Interest on these notes is payable semi-annually in arrears on June 15th and December 15th of each year. (8) Interest on these notes is payable semi-annually in arrears on February 17th and August 17th of each year. (9) Interest on these notes is payable semi-annually in arrears on April 1st and October 1st of each year. (10) Interest on these notes is payable semi-annually in arrears on February 15th and August 15th of each year. (11) Interest on these notes is payable semi-annually in arrears on January 15th and July 15th of each year.

Deferred Revenue and Acquisit_2

Deferred Revenue and Acquisition-Related Intangible Liabilities, net (Tables)	12 Months Ended
	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Deferred revenue and acquisition-related liabilities	Deferred revenue and acquisition-related intangible liabilities, net consisted of the following at December 31, 2020 and 2019: December 31, 2020 2019 (in thousands) Deferred revenue related to tenant-funded tenant improvements $ 88,645 $ 96,271 Other deferred revenue 26,533 19,125 Acquisition-related intangible liabilities, net (1) 13,345 24,092 Total $ 128,523 $139,488 _____________________ (1) See Note 5 “Deferred Leasing Costs and Acquisition-Related Intangible Assets and Liabilities, net” for additional information regarding our acquisition-related intangible liabilities.
Estimated amortization of deferred revenue related to tenant-funded improvements	The following is the estimated amortization of deferred revenue related to tenant-funded tenant improvements as of December 31, 2020 for the next five years and thereafter: Year Ending (in thousands) 2021 $ 16,216 2022 15,188 2023 13,367 2024 11,325 2025 8,564 Thereafter 23,985 Total $ 88,645

Stockholders' Equity of the C_2

Stockholders' Equity of the Company (Tables)	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Schedule of common stock sales under the at-the-market offering	The following table sets forth information regarding settlements of forward equity sale agreements under our at-the-market offering program for the year ended December 31, 2020: Year Ended December 31, 2020 (in millions, except share and per share data) Shares of common stock settled during the period 3,147,110 Weighted average price per share of common stock $ 80.08 Aggregate gross proceeds $ 252.0 Aggregate net proceeds after selling commissions $ 247.3 Year Ended December 31, 2018 (in millions, except share and per share data) Shares of common stock sold during the period 1,817,195 Weighted average price per share of common stock $ 73.64 Aggregate gross proceeds $ 133.8 Aggregate net proceeds after selling commissions $ 132.1
Schedule of accrued dividends and distributions	The following tables summarize accrued dividends and distributions for the noted outstanding shares of common stock and noncontrolling units as of December 31, 2020 and 2019: December 31, 2020 2019 (in thousands) Dividends and Distributions payable to: Common stockholders $ 58,018 $ 51,418 Noncontrolling common unitholders of the Operating Partnership 575 981 RSU holders (1) 838 820 Total accrued dividends and distribution to common stockholders and noncontrolling unitholders $ 59,431 $ 53,219 _____________________ (1) The amount includes the value of the dividend equivalents that will be paid with additional RSUs (see Note 15 “Share-Based and Other Compensation” for additional information).
Schedule of outstanding shares of common stock, preferred stock and noncontrolling units	December 31, 2020 2019 Outstanding Shares and Units: Common stock (1) 116,035,827 106,016,287 Noncontrolling common units 1,150,574 2,023,287 RSUs (2) 1,638,026 1,651,905 _____________________ (1) The amount includes nonvested shares. (2) The amount includes nonvested RSUs. Does not include 873,709 and 932,675 market measure-based RSUs because not all the necessary performance conditions have been met as of December 31, 2020 and 2019, respectively. Refer to Note 15 “Share-Based and Other Compensation” for additional information.

Partners' Capital of the Oper_2

Partners' Capital of the Operating Partnership (Tables)	12 Months Ended
	Dec. 31, 2020
Class of Stock [Line Items]
Schedule of common stock sales under the at-the-market offering	The following table sets forth information regarding settlements of forward equity sale agreements under our at-the-market offering program for the year ended December 31, 2020: Year Ended December 31, 2020 (in millions, except share and per share data) Shares of common stock settled during the period 3,147,110 Weighted average price per share of common stock $ 80.08 Aggregate gross proceeds $ 252.0 Aggregate net proceeds after selling commissions $ 247.3 Year Ended December 31, 2018 (in millions, except share and per share data) Shares of common stock sold during the period 1,817,195 Weighted average price per share of common stock $ 73.64 Aggregate gross proceeds $ 133.8 Aggregate net proceeds after selling commissions $ 132.1
Schedule of accrued dividends and distributions	The following tables summarize accrued dividends and distributions for the noted outstanding shares of common stock and noncontrolling units as of December 31, 2020 and 2019: December 31, 2020 2019 (in thousands) Dividends and Distributions payable to: Common stockholders $ 58,018 $ 51,418 Noncontrolling common unitholders of the Operating Partnership 575 981 RSU holders (1) 838 820 Total accrued dividends and distribution to common stockholders and noncontrolling unitholders $ 59,431 $ 53,219 _____________________ (1) The amount includes the value of the dividend equivalents that will be paid with additional RSUs (see Note 15 “Share-Based and Other Compensation” for additional information).
Schedule of outstanding shares of common stock, preferred stock and noncontrolling units	December 31, 2020 2019 Outstanding Shares and Units: Common stock (1) 116,035,827 106,016,287 Noncontrolling common units 1,150,574 2,023,287 RSUs (2) 1,638,026 1,651,905 _____________________ (1) The amount includes nonvested shares. (2) The amount includes nonvested RSUs. Does not include 873,709 and 932,675 market measure-based RSUs because not all the necessary performance conditions have been met as of December 31, 2020 and 2019, respectively. Refer to Note 15 “Share-Based and Other Compensation” for additional information.
Kilroy Realty L.P. [Member]
Class of Stock [Line Items]
Schedule of common stock sales under the at-the-market offering	During the year ended December 31, 2018, the Company utilized its at-the-market stock offering programs to issue shares of common stock. See Note 13 “Stockholders’ Equity of the Company” for additional information. The net offering proceeds contributed by the Company to the Operating Partnership in exchange for common units for the year ended December 31, 2020 and 2018 are as follows: Year Ended December 31, 2020 2018 (in millions except share and per share data) Shares of common stock contributed by the Company 3,147,110 1,817,195 Common units exchanged for shares of common stock by the Company 3,147,110 1,817,195 Aggregate gross proceeds $ 252.0 $ 133.8 Aggregate net proceeds after selling commissions $ 247.3 $ 132.1
Redeemable noncontrolling interest	The following table sets forth the number of common units held by the Company and the number of common units held by non-affiliated investors and certain of our executive officers and directors in the form of noncontrolling common units as well as the ownership interest held on each respective date: December 31, 2020 December 31, 2019 Company owned common units in the Operating Partnership 116,035,827 106,016,287 Company owned general partnership interest 99.0 % 98.1 % Noncontrolling common units of the Operating Partnership 1,150,574 2,023,287 Ownership interest of noncontrolling interest 1.0 % 1.9 %
Schedule of accrued dividends and distributions	The following tables summarize accrued distributions for the noted common units as of December 31, 2020 and 2019: December 31, 2020 December 31, 2019 (in thousands) Distributions payable to: General partner $ 58,018 $ 51,418 Common limited partners 575 981 RSU holders (1) 838 820 Total accrued distributions to common unitholders $ 59,431 $ 53,219 _____________________ (1) The amount includes the value of the dividend equivalents that will be paid with additional RSUs (see Note 15 “Share-Based and Other Compensation” for additional information).
Schedule of outstanding shares of common stock, preferred stock and noncontrolling units	December 31, 2020 December 31, 2019 Outstanding Units: Common units held by the general partner 116,035,827 106,016,287 Common units held by the limited partners 1,150,574 2,023,287 RSUs (1) 1,638,026 1,651,905 _____________________

Share-Based and Other Compens_2

Share-Based and Other Compensation (Tables)	12 Months Ended
	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of Restricted Stock Units Valuation Assumptions	As of December 31, 2020, the estimated number of RSUs earned for the 2020 and 2019 Performance-Based RSUs and the actual number of RSUs earned for the 2018 Performance-Based RSUs was as follows: 2020 Performance-Based RSUs 2019 Performance-Based RSUs 2018 Performance-Based RSUs Service vesting period January 31, 2020 - January, 2023 February 1, 2019 - January, 2022 February 14, 2018 - January, 2021 Target RSUs granted 154,267 143,396 158,205 Estimated RSUs earned (1) 142,004 220,151 229,748 Date of valuation January 31, 2020 February 1, 2019 February 14, 2018 _____________________ (1) Estimated RSUs earned for the 2020 Performance-Based RSUs are based on the actual achievement of the 2020 FFO Performance Condition and for the 2020 Debt to EBITDA Ratio Performance Condition, assumes 100% of the target level of achievement for all participants, and target level of achievement of the 2020 Market Condition. Estimated RSUs earned for the 2019 Performance-Based RSUs are based on the actual achievement of the 2019 FFO Performance Condition and assume target level achievement of the 2019 Market Condition and maximum level of achievement of the 2019 Debt to EBITDA Ratio Performance Condition. The 2018 Performance-Based RSUs earned are based on actual performance of the 2018 Performance Conditions and the 2018 Market Condition. 2020 Time-Based RSU Grant 2019 Time-Based RSU Grant December 2018 Time-Based RSU Grant 2018 Time-Based RSU Grant (1) Service vesting period January 31, 2020 - January 5, 2023 February 1, 2019 - January 5, 2022 December 27, 2018 - January 5, 2023 January & February 2018 - January 5, 2021 Fair value on valuation date (in millions) $ 9.0 $ 10.1 $ 18.5 $ 8.4 Fair value per share $ 82.57 $ 69.89 $ 62.00 $ 70.37 Date of fair valuation January 31, 2020 February 1, 2019 December 27, 2018 January & February 2018 ____________________
Summary of Nonvested Restricted Stock	A summary of our nonvested and vested restricted stock activity for the year ended December 31, 2018 is presented below: Shares Granted Shares Vested Years ended December 31, Nonvested Weighted-Average Grant Date Vested Shares Total Fair Value at Vest Date (1) (in thousands) 2018 — — (22,884) 1,652 _______________________ (1) Total fair value of shares vested was calculated based on the quoted closing share price of the Company’s common stock on the NYSE on the date of vesting.
Summary of Nonvested and Vested Restricted Stock Activity	A summary of our nonvested and vested restricted stock activity for the year ended December 31, 2018 is presented below: Shares Granted Shares Vested Years ended December 31, Nonvested Weighted-Average Grant Date Vested Shares Total Fair Value at Vest Date (1) (in thousands) 2018 — — (22,884) 1,652 _______________________ (1) Total fair value of shares vested was calculated based on the quoted closing share price of the Company’s common stock on the NYSE on the date of vesting.
December 2018 Market-Based RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Assumptions Utilized in the Monte Carlo Simulation Pricing Models	The following table summarizes the assumptions utilized in the Monte Carlo simulation pricing models: December 2018 Market-Based RSU Award Fair Value Assumptions Valuation date December 27, 2018 Fair value per share on valuation date $68.66 Expected share price volatility 23.0% Risk-free interest rate 2.4%
Market measure-based Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Summary of Restricted Stock Units Award Activity	A summary of our performance and market-measure based RSU activity from January 1, 2020 through December 31, 2020 is presented below: Nonvested RSUs Vested RSUs Total RSUs Amount Weighted-Average Outstanding at January 1, 2020 932,675 $ 71.04 36,679 969,354 Granted 154,267 85.08 38,313 192,580 Vested (230,334) 74.71 230,334 — Settled (1) — — (259,954) (259,954) Issuance of dividend equivalents (2) 29,561 62.21 1,407 30,968 Forfeited (12,460) 84.54 (4) (12,464) Outstanding as of December 31, 2020 (3) 873,709 $ 72.06 46,775 920,484 ____________________ (1) Represents vested RSUs that were settled in shares of the Company’s common stock. Total shares settled include 125,928 shares that were tendered in accordance with the terms of the 2006 Plan to satisfy minimum statutory tax withholding requirements related to the RSUs settled. We accept the return of RSUs at the current quoted closing share price of the Company’s common stock to satisfy tax obligations. (2) Represents the issuance of dividend equivalents earned on the underlying RSUs. The dividend equivalents vest based on terms specified under the related RSU award agreement. (3) Outstanding RSUs as of December 31, 2020 represent the actual achievement of the FFO performance conditions and assumes target levels for the market and other performance conditions. The number of restricted stock units ultimately earned is subject to change based upon actual performance over the three-year vesting period. Dividend equivalents earned will vest along with the underlying award and are also subject to changes based on the number of RSUs ultimately earned for each underlying award. A summary of our performance and market-measure based RSU activity for the years ended December 31, 2020, 2019 and 2018 is presented below: RSUs Granted RSUs Vested Years ended December 31, Non-Vested RSUs Granted (1) Weighted-Average Vested RSUs Total Vest-Date Fair Value 2020 154,267 $ 85.08 (270,054) $ 19,471 2019 231,191 71.12 (265,737) 18,703 2018 601,012 68.51 (265,918) 18,906 ____________________
Time-Based Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Summary of Restricted Stock Units Award Activity	A summary of our time-based RSU activity from January 1, 2020 through December 31, 2020 is presented below: Nonvested RSUs Vested RSUs Total RSUs Amount Weighted Average Fair Value Outstanding at January 1, 2020 543,848 $ 66.66 1,071,378 1,615,226 Granted 120,769 79.74 — 120,769 Vested (173,796) 70.83 173,796 — Settled (1) (181,462) (181,462) Issuance of dividend equivalents (2) 15,523 61.80 34,812 50,335 Forfeited (11,979) 77.58 — (11,979) Canceled (3) (1,638) (1,638) Outstanding as of December 31, 2020 494,365 $ 67.97 1,096,886 1,591,251 ____________________ (1) Represents vested RSUs that were settled in shares of the Company’s common stock. Total shares settled include 67,316 shares that were tendered in accordance with the terms of the 2006 Plan to satisfy minimum statutory tax withholding requirements related to the RSUs settled. We accept the return of RSUs at the current quoted closing share price of the Company’s common stock to satisfy tax obligations. (2) Represents the issuance of dividend equivalents earned on the underlying RSUs. The dividend equivalents vest based on terms specified under the related RSU award agreement. (3) For shares vested but not yet settled, we accept the return of RSUs at the current quoted closing share price of the Company’s common stock to satisfy minimum statutory tax-withholding requirements related to either the settlement or vesting of RSUs in accordance with the terms of the 2006 Plan. A summary of our time-based RSU activity for the years ended December 31, 2020, 2019 and 2018 is presented below: RSUs Granted RSUs Vested Year ended December 31, Non-Vested Weighted-Average Grant Date Vested RSUs Total Vest-Date Fair Value (1) (in thousands) 2020 120,769 $ 79.74 (208,608) $ 15,066 2019 153,005 70.31 (182,219) 12,227 2018 437,216 64.21 (214,131) 14,768 ____________________
2020, 2019, and 2018 Performance-Based RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Assumptions Utilized in the Monte Carlo Simulation Pricing Models	The following table summarizes the assumptions utilized in the Monte Carlo simulation pricing models: 2020 Award Fair Value Assumptions 2019 Award Fair Value Assumptions 2018 Award Fair Value Assumptions Valuation date January 31, 2020 February 1, 2019 February 14, 2018 Fair value per share on valuation date $84.54 $72.57 $70.08 Expected share price volatility 17.0% 19.0% 20.0% Risk-free interest rate 1.35% 2.48% 2.37%

Rental Income and Future Mini_2

Rental Income and Future Minimum Rent (Tables)	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Schedule of allocation of rental income between fixed and variable payments	The table below sets forth the allocation of rental income between fixed and variable payments and net collectability reversals or recoveries for the years ended December 31, 2020 and 2019: Year Ended December 31, 2020 2019 Fixed lease payments $ 786,860 $ 708,362 Variable lease payments 124,443 115,915 Net collectability (reversals) recoveries (1) (18,997) 2,195 Total rental income $ 892,306 $ 826,472 ____________________ (1) Represents adjustments to rental income related to our assessment of the collectability of amounts due under leases with our tenants. For the year ended December 31, 2020, includes $18.4 million of write - offs related to the cumulative impact of transitioning certain tenants to a cash basis of reporting primarily as a result of the COVID-19 pandemic. Also includes a $0.6 million net increase to the allowance for doubtful accounts, which includes the impact of $2.2 million of reversals to the allowance for doubtful account for tenants that had an allowance at January 1, 2020 and were subsequently transitioned to a cash basis of reporting during 2020. These reversals are included in the $18.4 million of write - offs above.
Future contractual minimum rent under operating lease	Future contractual minimum rent under operating leases, which includes amounts contractually due from leases that are on a cash basis of reporting due to creditworthiness considerations, as of December 31, 2020 for future periods is summarized as follows: Year Ending (in thousands) 2021 $ 731,169 2022 804,488 2023 788,214 2024 750,051 2025 719,274 Thereafter 3,455,201 Total (1) $ 7,248,397 ____________________ (1) Excludes residential leases and leases with a term of one year or less.

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Schedule of contractual expiration dates for ground leases	The following table summarizes our properties that are held subject to long-term noncancellable ground lease obligations and the respective contractual expiration dates: Property Contractual Expiration Date (1) 601 108th Ave NE, Bellevue, WA November 2093 701, 801 and 837 N. 34th Street, Seattle, WA (2) December 2041 1701 Page Mill Road and 3150 Porter Drive, Palo Alto, CA December 2067 Kilroy Airport Center Phases I, II, and III, Long Beach, CA July 2084 3243 S. La Cienega Boulevard, Los Angeles, CA (3) October 2106 ____________________ (1) Reflects the contractual expiration date prior to the impact of any extension or purchase options held by the Company. (2) The Company has three 10-year and one 45-year extension options for this ground lease, which if exercised would extend the expiration date to December 2116. These extension options are not assumed to be exercised in our calculation of the present value of the future minimum lease payments for this lease.
Schedule of minimum commitment under ground leases	The minimum commitment under our ground leases as of December 31, 2020 for future periods is as follows: Year Ending (in thousands) 2021 $ 5,641 2022 5,642 2023 5,662 2024 5,662 2025 5,662 Thereafter 280,723 Total undiscounted cash flows (1)(2)(3)(4)(5)(6) $ 308,992 Present value discount (211,214) Ground lease liabilities $ 97,778 ________________________ (1) Excludes contingent future rent payments based on gross income or adjusted gross income and reflects the minimum ground lease obligations before the impact of ground lease extension options. (2) One of our ground lease obligations is subject to a fair market value adjustment every five years; however, the lease includes ground rent subprotection and infrastructure rent credits which currently limit our annual rental obligations to $1.0 million. The contractual obligations for that ground lease included above assumes the lesser of $1.0 million or annual lease rental obligation in effect as of December 31, 2020. (3) One of our ground lease obligations includes a component which is based on the percentage of gross income that exceeds the minimum ground rent. The minimum rent is subject to increases every five years based on 50% of the average annual percentage rent for the previous five years. The contractual obligations for that lease included above assume the current annual ground lease obligation in effect at December 31, 2020 for the remainder of the lease term since we cannot predict future adjustments. (4) One of our ground lease obligations is subject to a fair market value adjustment every five years based on a combination of CPI adjustments and third-party appraisals limited to maximum increases annually. The contractual obligations for that lease included above assume the current annual ground lease obligation in effect at December 31, 2020 for the remainder of the lease term since we cannot predict future adjustments. (5) One of our ground lease obligations includes a component which is based on the percentage of adjusted gross income that exceeds the minimum ground rent. The minimum rent is subject to increases every 10 years by an amount equal to 60% of the average annual percentage rent for the previous three years. The contractual obligations for this lease included above assume the current annual ground lease obligation in effect at December 31, 2020 for the remainder of the lease term since we cannot predict future adjustments.

Fair Value Measurements and D_2

Fair Value Measurements and Disclosures (Tables)	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair value of the company's marketable securities	The following table sets forth the fair value of our marketable securities as of December 31, 2020 and 2019: Fair Value (Level 1) (1) 2020 2019 Description (in thousands) Marketable securities (2) $ 27,481 $ 27,098 ____________________ (1) Based on quoted prices in active markets for identical securities. (2) The marketable securities are held in a limited rabbi trust .
Net (loss) gain on marketable securities	The following table sets forth the net gain (loss) on marketable securities recorded during the years ended December 31, 2020, 2019 and 2018: December 31, 2020 2019 2018 Description (in thousands) Net gain (loss) on marketable securities $ 2,864 $ 3,885 $ (1,851)
Carrying value and fair value of other financial instruments	The following table sets forth the carrying value and the fair value of our other financial instruments as of December 31, 2020 and 2019: December 31, 2020 2019 Carrying Value Fair Value (1) Carrying Value Fair Value (1) (in thousands) Liabilities Secured debt, net $ 253,582 $ 282,559 $ 258,593 $ 272,997 Unsecured debt, net 3,670,099 4,089,339 3,049,185 3,252,217 Unsecured line of credit — — 245,000 245,195 _______________ (1) Fair value calculated using Level II inputs, which are based on model-derived valuations in which significant inputs and significant value drivers are observable in active markets.

Net Income Available to Commo_3

Net Income Available to Common Stockholders Per Share of the Company (Tables)	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Net income available to common stockholders	The following table reconciles the numerator and denominator in computing the Company’s basic and diluted per-share computations for net income available to common stockholders for the years ended December 31, 2020, 2019 and 2018: Year Ended December 31, 2020 2019 2018 (in thousands, except unit and per unit amounts) Numerator: Net income attributable to common stockholders $ 187,105 $ 195,443 $ 258,415 Allocation to participating securities (1) (2,229) (2,119) (2,004) Numerator for basic and diluted net income available to common stockholders $ 184,876 $ 193,324 $ 256,411 Denominator: Basic weighted average vested shares outstanding 113,241,341 103,200,568 99,972,359 Effect of dilutive securities 478,281 648,600 510,006 Diluted weighted average vested shares and common stock equivalents outstanding 113,719,622 103,849,168 100,482,365 Basic earnings per share: Net income available to common stockholders per share $ 1.63 $ 1.87 $ 2.56 Diluted earnings per share: Net income available to common stockholders per share $ 1.63 $ 1.86 $ 2.55 _____________________ (1) Participating securities include nonvested shares, certain time-based RSUs and vested market measure-based RSUs.

Net Income Available to Commo_4

Net Income Available to Common Unitholders Per Unit of the Operating Partnership (Tables)	12 Months Ended
	Dec. 31, 2020
Net Income Available To Common Unitholders [Line Items]
Net income available to common unitholders	The following table reconciles the numerator and denominator in computing the Company’s basic and diluted per-share computations for net income available to common stockholders for the years ended December 31, 2020, 2019 and 2018: Year Ended December 31, 2020 2019 2018 (in thousands, except unit and per unit amounts) Numerator: Net income attributable to common stockholders $ 187,105 $ 195,443 $ 258,415 Allocation to participating securities (1) (2,229) (2,119) (2,004) Numerator for basic and diluted net income available to common stockholders $ 184,876 $ 193,324 $ 256,411 Denominator: Basic weighted average vested shares outstanding 113,241,341 103,200,568 99,972,359 Effect of dilutive securities 478,281 648,600 510,006 Diluted weighted average vested shares and common stock equivalents outstanding 113,719,622 103,849,168 100,482,365 Basic earnings per share: Net income available to common stockholders per share $ 1.63 $ 1.87 $ 2.56 Diluted earnings per share: Net income available to common stockholders per share $ 1.63 $ 1.86 $ 2.55 _____________________ (1) Participating securities include nonvested shares, certain time-based RSUs and vested market measure-based RSUs.
Kilroy Realty L.P. [Member]
Net Income Available To Common Unitholders [Line Items]
Net income available to common unitholders	The following table reconciles the numerator and denominator in computing the Operating Partnership’s basic and diluted per-unit computations for net income available to common unitholders for the years ended December 31, 2020, 2019 and 2018: Year Ended December 31, 2020 2019 2018 (in thousands, except unit and per unit amounts) Numerator: Net income attributable to common unitholders $ 189,609 $ 198,738 $ 263,210 Allocation to participating securities (1) (2,229) (2,119) (2,004) Numerator for basic and diluted net income available to common unitholders $ 187,380 $ 196,619 $ 261,206 Denominator: Basic weighted average vested units outstanding 115,095,506 105,223,975 102,025,276 Effect of dilutive securities 478,281 648,600 510,006 Diluted weighted average vested units and common unit equivalents outstanding 115,573,787 105,872,575 102,535,282 Basic earnings per unit: Net income available to common unitholders per unit $ 1.63 $ 1.87 $ 2.56 Diluted earnings per unit: Net income available to common unitholders per unit $ 1.62 $ 1.86 $ 2.55 ____________________ (1) Participating securities include nonvested shares, certain time-based RSUs and vested market measure-based RSUs.

Supplemental Cash Flow Inform_3

Supplemental Cash Flow Information of the Company (Tables)	12 Months Ended
	Dec. 31, 2020
Supplemental Cash Flow Elements [Abstract]
Schedule of supplemental cash flows	Supplemental cash flow information follows (in thousands): Year Ended December 31, 2020 2019 2018 SUPPLEMENTAL CASH FLOWS INFORMATION: Cash paid for interest, net of capitalized interest of $75,852, $77,666, and $65,627 as of December 31, 2020, 2019 and 2018, respectively $ 61,741 $ 43,607 $ 44,697 Cash paid for amounts included in the measurement of ground lease liabilities $ 5,744 $ 5,224 $ 4,398 NON-CASH INVESTING TRANSACTIONS: Accrual for expenditures for operating properties and development properties $ 189,161 $ 162,654 $ 158,626 Tenant improvements funded directly by tenants $ 11,592 $ 10,268 $ 13,968 Assumption of accrued liabilities in connection with acquisitions (Note 3) $ — $ 10,267 $ 40,624 Initial measurement of operating right of use ground lease assets (Notes 2, 3 and 18) $ — $ 96,272 $ — Initial measurement of operating ground lease liabilities (Notes 2, 3 and 18) $ — $ 98,349 $ — NON-CASH FINANCING TRANSACTIONS: Accrual of dividends and distributions payable to common stockholders and common $ 59,431 $ 53,219 $ 47,559 Exchange of common units of the Operating Partnership into shares of the Company’s $ 37,640 $ 78 $ 1,962 Supplemental cash flow information follows (in thousands): Year Ended December 31, 2020 2019 2018 SUPPLEMENTAL CASH FLOWS INFORMATION: Cash paid for interest, net of capitalized interest of $75,852, $77,666, and $65,627 as of December 31, 2020, 2019 and 2018, respectively $ 61,741 $ 43,607 $ 44,697 Cash paid for amounts included in the measurement of ground lease liabilities $ 5,744 $ 5,224 $ 4,398 NON-CASH INVESTING TRANSACTIONS: Accrual for expenditures for operating properties and development properties $ 189,161 $ 162,654 $ 158,626 Tenant improvements funded directly by tenants $ 11,592 $ 10,268 $ 13,968 Assumption of accrued liabilities in connection with acquisitions (Note 3) $ — $ 10,267 $ 40,624 Initial measurement of operating right of use ground lease assets (Notes 2, 3 and 18) $ — $ 96,272 $ — Initial measurement of operating ground lease liabilities (Notes 2, 3 and 18) $ — $ 98,349 $ — NON-CASH FINANCING TRANSACTIONS: Accrual of distributions payable to common unitholders (Notes 14 and 27) $ 59,431 $ 53,219 $ 47,559
Reconciliation of cash and cash equivalents and restricted cash	The following is a reconciliation of our cash and cash equivalents and restricted cash at the beginning and end of the years ended December 31, 2020, 2019 and 2018. Year Ended December 31, 2020 2019 2018 RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH: Cash and cash equivalents at beginning of period $ 60,044 $ 51,604 $ 57,649 Restricted cash at beginning of period 16,300 119,430 9,149 Cash and cash equivalents and restricted cash at beginning of period $ 76,344 $ 171,034 $ 66,798 Cash and cash equivalents at end of period $ 731,991 $ 60,044 $ 51,604 Restricted cash at end of period 91,139 16,300 119,430 Cash and cash equivalents and restricted cash at end of period $ 823,130 $ 76,344 $ 171,034 The following is a reconciliation of our cash and cash equivalents and restricted cash at the beginning and end of the years ended December 31, 2020, 2019 and 2018. Year Ended December 31, 2020 2019 2018 RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH: Cash and cash equivalents at beginning of period $ 60,044 $ 51,604 $ 57,649 Restricted cash at beginning of period 16,300 119,430 9,149 Cash and cash equivalents and restricted cash at beginning of period $ 76,344 $ 171,034 $ 66,798 Cash and cash equivalents at end of period $ 731,991 $ 60,044 $ 51,604 Restricted cash at end of period 91,139 16,300 119,430 Cash and cash equivalents and restricted cash at end of period $ 823,130 $ 76,344 $ 171,034

Supplemental Cash Flow Elements

Supplemental Cash Flow Elements (Tables)	12 Months Ended
	Dec. 31, 2020
Supplemental Cash Flow Elements [Abstract]
Schedule of supplemental cash flows, operating unit	Supplemental cash flow information follows (in thousands): Year Ended December 31, 2020 2019 2018 SUPPLEMENTAL CASH FLOWS INFORMATION: Cash paid for interest, net of capitalized interest of $75,852, $77,666, and $65,627 as of December 31, 2020, 2019 and 2018, respectively $ 61,741 $ 43,607 $ 44,697 Cash paid for amounts included in the measurement of ground lease liabilities $ 5,744 $ 5,224 $ 4,398 NON-CASH INVESTING TRANSACTIONS: Accrual for expenditures for operating properties and development properties $ 189,161 $ 162,654 $ 158,626 Tenant improvements funded directly by tenants $ 11,592 $ 10,268 $ 13,968 Assumption of accrued liabilities in connection with acquisitions (Note 3) $ — $ 10,267 $ 40,624 Initial measurement of operating right of use ground lease assets (Notes 2, 3 and 18) $ — $ 96,272 $ — Initial measurement of operating ground lease liabilities (Notes 2, 3 and 18) $ — $ 98,349 $ — NON-CASH FINANCING TRANSACTIONS: Accrual of dividends and distributions payable to common stockholders and common $ 59,431 $ 53,219 $ 47,559 Exchange of common units of the Operating Partnership into shares of the Company’s $ 37,640 $ 78 $ 1,962 Supplemental cash flow information follows (in thousands): Year Ended December 31, 2020 2019 2018 SUPPLEMENTAL CASH FLOWS INFORMATION: Cash paid for interest, net of capitalized interest of $75,852, $77,666, and $65,627 as of December 31, 2020, 2019 and 2018, respectively $ 61,741 $ 43,607 $ 44,697 Cash paid for amounts included in the measurement of ground lease liabilities $ 5,744 $ 5,224 $ 4,398 NON-CASH INVESTING TRANSACTIONS: Accrual for expenditures for operating properties and development properties $ 189,161 $ 162,654 $ 158,626 Tenant improvements funded directly by tenants $ 11,592 $ 10,268 $ 13,968 Assumption of accrued liabilities in connection with acquisitions (Note 3) $ — $ 10,267 $ 40,624 Initial measurement of operating right of use ground lease assets (Notes 2, 3 and 18) $ — $ 96,272 $ — Initial measurement of operating ground lease liabilities (Notes 2, 3 and 18) $ — $ 98,349 $ — NON-CASH FINANCING TRANSACTIONS: Accrual of distributions payable to common unitholders (Notes 14 and 27) $ 59,431 $ 53,219 $ 47,559
Reconciliation of cash and cash equivalents and restricted cash	The following is a reconciliation of our cash and cash equivalents and restricted cash at the beginning and end of the years ended December 31, 2020, 2019 and 2018. Year Ended December 31, 2020 2019 2018 RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH: Cash and cash equivalents at beginning of period $ 60,044 $ 51,604 $ 57,649 Restricted cash at beginning of period 16,300 119,430 9,149 Cash and cash equivalents and restricted cash at beginning of period $ 76,344 $ 171,034 $ 66,798 Cash and cash equivalents at end of period $ 731,991 $ 60,044 $ 51,604 Restricted cash at end of period 91,139 16,300 119,430 Cash and cash equivalents and restricted cash at end of period $ 823,130 $ 76,344 $ 171,034 The following is a reconciliation of our cash and cash equivalents and restricted cash at the beginning and end of the years ended December 31, 2020, 2019 and 2018. Year Ended December 31, 2020 2019 2018 RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH: Cash and cash equivalents at beginning of period $ 60,044 $ 51,604 $ 57,649 Restricted cash at beginning of period 16,300 119,430 9,149 Cash and cash equivalents and restricted cash at beginning of period $ 76,344 $ 171,034 $ 66,798 Cash and cash equivalents at end of period $ 731,991 $ 60,044 $ 51,604 Restricted cash at end of period 91,139 16,300 119,430 Cash and cash equivalents and restricted cash at end of period $ 823,130 $ 76,344 $ 171,034

Tax Treatment of Distributions

Tax Treatment of Distributions (Tables)	12 Months Ended
	Dec. 31, 2020
Class of Stock [Line Items]
Reconciliation of dividends declared to dividends paid	The following table reconciles the dividends declared per share of common stock to the dividends paid per share of common stock during the years ended December 31, 2020, 2019 and 2018 as follows: Year Ended December 31, Dividends 2020 2019 2018 Dividends declared per share of common stock $ 1.970 $ 1.910 $ 1.790 Less: Dividends declared in the current year and paid in the following year (0.500) (0.485) (0.455) Add: Dividends declared in the prior year and paid in the current year 0.485 0.455 0.425 Dividends paid per share of common stock $ 1.955 $ 1.880 $ 1.760
Common Stock [Member]
Class of Stock [Line Items]
Reconciliation of dividends declared to dividends paid	The unaudited income tax treatment for the dividends to common stockholders reportable for the years ended December 31, 2020, 2019 and 2018 as identified in the table above was as follows: Year Ended December 31, Shares of Common Stock 2020 2019 2018 Ordinary income (1) $ 1.474 75.40 % $ 0.939 49.95 % $ 1.474 83.73 % Qualified dividend 0.002 0.12 0.004 0.21 0.003 0.19 Return of capital 0.162 8.30 0.312 16.62 0.275 15.64 Capital gains (2) 0.275 14.05 0.600 31.93 0.008 0.44 Unrecaptured section 1250 gains 0.042 2.13 0.025 1.29 — — $ 1.955 100.00 % $ 1.880 100.00 % $ 1.760 100.00 % ____________________ (1) The Tax Cuts and Jobs Act enacted on December 22, 2017 generally allows a deduction for noncorporate taxpayers equal to 20% of ordinary dividends distributed by a REIT (excluding capital gain dividends and qualified dividend income). The amount of dividend eligible for this deduction is referred to as the Section 199A Dividend. For the year ended December 31, 2020, the Section 199A Dividend is equal to the total ordinary income dividend. (2) Capital gains are comprised entirely of 20% rate gains.

Quarterly Financial Informati_3

Quarterly Financial Information of the Company (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2020
Quarterly Financial Information Disclosure [Abstract]
Schedule of summarized quarterly financial data	Summarized quarterly financial data for the years ended December 31, 2020 and 2019 was as follows: 2020 Quarter Ended (1) March 31, June 30, September 30, December 31, (in thousands, except per share amounts) Revenues $ 221,328 $ 219,423 $ 228,314 $ 229,332 Net income 45,418 24,352 54,071 83,452 Net income attributable to Kilroy Realty Corporation 39,817 19,618 49,028 78,642 Net income available to common stockholders 39,817 19,618 49,028 78,642 Net income available to common stockholders per share – basic 0.37 0.17 0.42 0.67 Net income available to common stockholders per share – diluted 0.37 0.17 0.42 0.67 2019 Quarter Ended (1) March 31, June 30, September 30, December 31, (in thousands, except per share amounts) Revenues $ 201,202 $ 200,492 $ 215,525 $ 220,235 Net income 41,794 47,215 48,298 77,922 Net income attributable to Kilroy Realty Corporation 36,903 42,194 43,846 72,500 Net income available to common stockholders 36,903 42,194 43,846 72,500 Net income available to common stockholders per share – basic 0.36 0.41 0.41 0.68 Net income available to common stockholders per share – diluted 0.36 0.41 0.41 0.67 ____________________

Quarterly Financial Informati_4

Quarterly Financial Information of the Operating Partnership (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2020
Schedule of summarized quarterly financial data	Summarized quarterly financial data for the years ended December 31, 2020 and 2019 was as follows: 2020 Quarter Ended (1) March 31, June 30, September 30, December 31, (in thousands, except per share amounts) Revenues $ 221,328 $ 219,423 $ 228,314 $ 229,332 Net income 45,418 24,352 54,071 83,452 Net income attributable to Kilroy Realty Corporation 39,817 19,618 49,028 78,642 Net income available to common stockholders 39,817 19,618 49,028 78,642 Net income available to common stockholders per share – basic 0.37 0.17 0.42 0.67 Net income available to common stockholders per share – diluted 0.37 0.17 0.42 0.67 2019 Quarter Ended (1) March 31, June 30, September 30, December 31, (in thousands, except per share amounts) Revenues $ 201,202 $ 200,492 $ 215,525 $ 220,235 Net income 41,794 47,215 48,298 77,922 Net income attributable to Kilroy Realty Corporation 36,903 42,194 43,846 72,500 Net income available to common stockholders 36,903 42,194 43,846 72,500 Net income available to common stockholders per share – basic 0.36 0.41 0.41 0.68 Net income available to common stockholders per share – diluted 0.36 0.41 0.41 0.67 ____________________
Kilroy Realty L.P. [Member]
Schedule of summarized quarterly financial data	Summarized quarterly financial data for the years ended December 31, 2020 and 2019 was as follows: 2020 Quarter Ended (1) March 31, June 30, September 30, December 31, (in thousands, except per unit amounts) Revenues $ 221,328 $ 219,423 $ 228,314 $ 229,332 Net income 45,418 24,352 54,071 83,452 Net income attributable to the Operating Partnership 40,389 19,838 49,728 79,654 Net income available to common unitholders 40,389 19,838 49,728 79,654 Net income available to common unitholders per unit – basic 0.37 0.16 0.42 0.67 Net income available to common unitholders per unit – diluted 0.36 0.16 0.42 0.67 2019 Quarter Ended (1) March 31, June 30, September 30, December 31, (in thousands, except per unit amounts) Revenues $ 201,202 $ 200,492 $ 215,525 $ 220,235 Net income 41,794 47,215 48,298 77,922 Net income attributable to the Operating Partnership 37,508 42,901 44,589 73,740 Net income available to common unitholders 37,508 42,901 44,589 73,740 Net income available to common unitholders per unit – basic 0.36 0.41 0.41 0.68 Net income available to common unitholders per unit – diluted 0.36 0.41 0.41 0.67 ______________________

Organization and Ownership (Det

Organization and Ownership (Details)	Dec. 31, 2020ft²propertyresidential_unitbuildingprojecttenant
Real Estate Properties [Line Items]
Rentable Square Feet	14,620,166
Stabilized office properties [Member]
Real Estate Properties [Line Items]
Number of buildings | building	117
Rentable Square Feet	14,620,166
Number of Tenants | tenant	447
Percentage Occupied	91.20%
Percentage Leased (unaudited)	94.30%
Stabilized residential properties [Member]
Real Estate Properties [Line Items]
Number of buildings | property	2
Percentage Occupied	72.00%
Number of residential units | property	808
In-process development projects - tenant improvement [Member]
Real Estate Properties [Line Items]
Number of buildings | property	3
Rentable Square Feet	1,080,000
In-process development projects - under construction [Member]
Real Estate Properties [Line Items]
Number of buildings | project	3
Rentable Square Feet	856,000
Number of residential units | residential_unit	193

Organization and Ownership - Na

Organization and Ownership - Narrative (Details)	12 Months Ended
	Dec. 31, 2020ft²apropertybuildingproperty_partnershipproject	Dec. 31, 2019
Real Estate Properties [Line Items]
Lease-up properties occupancy percentage	95.00%
Lease-up properties occupancy duration	1 year
Stabilized Residential Units in San Diego, CA [Member]
Real Estate Properties [Line Items]
Number of Units	608
101 First LLC and 303 Second LLC [Member]
Real Estate Properties [Line Items]
Number of properties | property_partnership	2
Ownership interest	56.00%
Redwood LLC [Member]
Real Estate Properties [Line Items]
Ownership interest	93.00%
Operating Partnership [Member]
Real Estate Properties [Line Items]
Number of properties | property_partnership	3
Ownership interest	99.00%	98.10%
Operating Partnership [Member] | Non-Affiliated Investors [Member]
Real Estate Properties [Line Items]
Ownership interest of noncontrolling interest	1.00%	1.90%
Washington [Member]
Real Estate Properties [Line Items]
Number of properties	8
Number of development projects	1
Number of future development projects	1
Stabilized Portfolio [Member]
Real Estate Properties [Line Items]
Number of development projects	4
Office properties [Member]
Real Estate Properties [Line Items]
Number of properties | building	117
Office properties [Member] | Operating Partnership [Member]
Real Estate Properties [Line Items]
Number of properties	4
Office properties [Member] | San Francisco, California [Member] | 101 First LLC and 303 Second LLC [Member]
Real Estate Properties [Line Items]
Number of properties	1
Office properties [Member] | Redwood City, California [Member] | Redwood LLC [Member]
Real Estate Properties [Line Items]
Number of properties	2
Development sites [Member]
Real Estate Properties [Line Items]
Number of properties | project	5
Area of undeveloped land | a	61
Properties and development projects [Member]
Real Estate Properties [Line Items]
Property ownership percentage	100.00%
Development Project in San Francisco [Member] | Stabilized Office Properties [Member] | San Francisco, California [Member]
Real Estate Properties [Line Items]
Area of real estate property | ft²	750,370
Development Project in Hollywood [Member] | Stabilized Office Properties [Member] | Hollywood, California [Member]
Real Estate Properties [Line Items]
Area of real estate property | ft²	361,388
Development Project in San Diego, California [Member] | Stabilized Retail Space [Member] | San Diego, California [Member]
Real Estate Properties [Line Items]
Area of real estate property | ft²	95,871

Basis of Presentation and Sig_4

Basis of Presentation and Significant Accounting Policies - Narrative (Details)	3 Months Ended	12 Months Ended
	Dec. 31, 2019USD ($)propertyinvestment	Dec. 31, 2020USD ($)propertysegmentvariable_interest_entityinvestmentproperty_partnership	Dec. 31, 2019USD ($)propertyproperty_partnershipvariable_interest_entityinvestment	Dec. 31, 2018USD ($)
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of VIEs | variable_interest_entity		2	4
Assets	$ 8,900,094,000	$ 10,000,708,000	$ 8,900,094,000
Liabilities	4,329,236,000	4,723,387,000	4,329,236,000
Noncontrolling interest in consolidated subsidiary	$ 195,431,000	$ 197,503,000	$ 195,431,000
Number of equity method investments | investment	0	0	0
Number of properties classified as held for sale | property	0	0	0
Number of consolidated property partnerships | property_partnership		3
Conversion ratio		1
Income tax provision		$ 0	$ 0	$ 0
Number of operating segments | segment		1
Washington [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of buildings | property		8
Number of development projects | property		1
Number of future development projects | property		1
Building and building improvements [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Depreciation of real estate		$ 244,800,000	211,900,000	$ 198,600,000
Minimum [Member] | Building and building improvements [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Property depreciable lives		25 years
Minimum [Member] | Leasehold improvements [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Property depreciable lives		1 year
Maximum [Member] | Building and building improvements [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Property depreciable lives		40 years
Maximum [Member] | Leasehold improvements [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Property depreciable lives		20 years
Lease Agreements [Member] | Minimum [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Finite-lived intangible asset, useful life		1 year
Lease Agreements [Member] | Maximum [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Finite-lived intangible asset, useful life		20 years
Disposal group, disposed of by sale [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Restricted cash	$ 0	$ 74,900,000	$ 0
100 First LLC and 303 Second LLC [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of VIEs | property_partnership			2
Number of buildings | property_partnership		2
Section 1031 Exchange [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of VIEs | property	2
Finance Partnership [Member] | Kilroy Realty Finance, Inc. [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Percentage of general partnership interest owned by wholly-owned subsidiary of the Company			1.00%
Variable Interest Entity, Primary Beneficiary [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Assets	$ 676,700,000	$ 469,300,000	$ 676,700,000
Liabilities	40,100,000	33,900,000	40,100,000
Variable Interest Entity, Primary Beneficiary [Member] | 100 First LLC and 303 Second LLC [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Noncontrolling interest in consolidated subsidiary	189,600,000	191,900,000	189,600,000
Variable Interest Entity, Primary Beneficiary [Member] | Real estate investment [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Assets	$ 598,000,000	$ 394,600,000	$ 598,000,000

Acquisitions - Operating Proper

Acquisitions - Operating Property Acquisitions (Details) $ in Millions	Oct. 15, 2019USD ($)ft²property	Dec. 31, 2020ft²property	Dec. 31, 2019USD ($)property
Schedule of Asset Acquisitions, by Acquisition [Line Items]
Number of buildings acquired | property		0
Rentable Square Feet (unaudited) | ft²		14,620,166
Purchase price			$ 173
3101-3243 La Cienega Boulevard, Culver City, CA [Member]
Schedule of Asset Acquisitions, by Acquisition [Line Items]
Number of buildings acquired | property	19		19
Rentable Square Feet (unaudited) | ft²	151,908
Purchase price	$ 186
Revenue contributed from acquired properties			$ 3.7
Net income (loss) contributed from acquired properties			$ (0.1)

Acquisitions - Estimated Fair V

Acquisitions - Estimated Fair Values of Assets and Liabilities Assumed (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)
Assets
Land and improvements	$ 150,561
Buildings and improvements	30,932
Deferred leasing costs and acquisition-related intangible assets	12,063
Right of use ground lease asset	13,334
Total assets acquired	206,890
Liabilities
Acquisition-related intangible liabilities	9,950
Ground lease liability	10,940
Total liabilities assumed	20,890
Net assets and liabilities acquired	$ 186,000
Discount rate	4.79%
Below-market leases acquired	$ 10,000
Weighted average amortization period of below-market leases	3 years 6 months
In-place leases [Member]
Assets
Deferred leasing costs and acquisition-related intangible assets	$ 9,200
Liabilities
Weighted average amortization period of above-market leases in years	3 years 3 months 18 days
Deferred leasing costs [Member]
Assets
Deferred leasing costs and acquisition-related intangible assets	$ 2,900
Liabilities
Weighted average amortization period of above-market leases in years	3 years 6 months

Acquisitions - Development Proj

Acquisitions - Development Project Acquisitions and Acquisition Costs (Details) - USD ($) $ in Thousands	Dec. 12, 2019	Aug. 19, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Asset Acquisitions, by Acquisition [Line Items]
Purchase price				$ 173,000
Asset acquisition, accrued liabilities				20,890
Restricted cash			$ 91,139	16,300	$ 119,430	$ 9,149
Payments to acquire land parcel				99,500
Acquisition costs, capitalized			300	1,600	$ 3,800
1335 Broadway & 901 Park Boulevard, San Diego, CA [Member]
Schedule of Asset Acquisitions, by Acquisition [Line Items]
Purchase price		$ 40,000
Asset acquisition, accrued liabilities		$ 4,000
Seattle CBD Project [Member]
Schedule of Asset Acquisitions, by Acquisition [Line Items]
Purchase price	$ 133,000
Asset acquisition, accrued liabilities				6,300
Restricted cash			$ 10,000	$ 10,000

Dispositions - Operating Proper

Dispositions - Operating Property Dispositions (Details) $ in Thousands	1 Months Ended				12 Months Ended
	Oct. 31, 2019USD ($)ft²property	May 31, 2019USD ($)ft²property	Dec. 31, 2018USD ($)ft²property	Nov. 30, 2018USD ($)ft²property	Dec. 31, 2020USD ($)ft²property	Dec. 31, 2019USD ($)ft²property	Dec. 31, 2018USD ($)ft²property
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rentable square feet | ft²					14,620,166
Gains on sales of operating properties | $					$ 35,536	$ 36,802	$ 142,926
Disposal group, disposed of by sale [Member] | 2020 Dispositions [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of buildings | property					1
Rentable square feet | ft²					87,147
Proceeds from sale of property held-for-sale | $					$ 75,900
Disposal group, disposed of by sale [Member] | 331 Fairchild Drive, Mountain View, CA [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of buildings | property					1
Rentable square feet | ft²					87,147
Proceeds from sale of property held-for-sale | $					$ 75,900
Disposal group, disposed of by sale [Member] | 2019 Dispositions [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of buildings | property						2
Rentable square feet | ft²						355,654
Proceeds from sale of property held-for-sale | $						$ 133,800
Disposal group, disposed of by sale [Member] | 2829 Townsgate Road, Thousand Oaks, CA [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of buildings | property		1
Rentable square feet | ft²		84,098
Proceeds from sale of property held-for-sale | $		$ 18,300
Disposal group, disposed of by sale [Member] | 2211 Michelson Drive Irvine CA [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of buildings | property	1
Rentable square feet | ft²	271,556
Proceeds from sale of property held-for-sale | $	$ 115,500
Disposal group, disposed of by sale [Member] | 2018 Dispositions [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of buildings | property			11				11
Rentable square feet | ft²			772,246				772,246
Proceeds from sale of property held-for-sale | $							$ 373,000
Disposal group, disposed of by sale [Member] | 1325-1327 Chesapeake Terrace, Sunnyvale, CA [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of buildings | property				4
Rentable square feet | ft²				266,982
Proceeds from sale of property held-for-sale | $				$ 160,300
Disposal group, disposed of by sale [Member] | Plaza Yarrow Bay Properties [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of buildings | property				4
Rentable square feet | ft²				279,924
Proceeds from sale of property held-for-sale | $				$ 134,500
Disposal group, disposed of by sale [Member] | 23925, 23975, & 24025 Park Sorrento, Calabasas, CA [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of buildings | property			3				3
Rentable square feet | ft²			225,340				225,340
Proceeds from sale of property held-for-sale | $			$ 78,200

Dispositions - Land Disposition

Dispositions - Land Dispositions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net gain (loss) on sales of land	$ 0	$ 0	$ 11,825
Disposal group, disposed of by sale [Member] | Plaza Yarrow Bay Properties [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net gain (loss) on sales of land			$ 11,800

Dispositions - Restricted Cash

Dispositions - Restricted Cash Related to Dispositions (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Disposal group, disposed of by sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Restricted cash	$ 74,900,000	$ 0

Deferred Leasing Costs and Ac_3

Deferred Leasing Costs and Acquisition-Related Intangible Assets and Liabilities, net - Deferred Leasing Costs and Acquisition-related Intangible Assets and Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, Net
Total deferred leasing costs and acquisition-related intangible assets, net	$ 210,949	$ 212,805
Acquisition-related Intangible Liabilities, Net [Abstract]
Total acquisitions-related intangible liabilities, net	13,345	24,092
Deferred leasing costs [Member]
Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, Net
Finite-lived intangible assets/liabilities, gross	300,556	286,026
Accumulated amortization	(104,277)	(100,145)
Finite-lived intangible assets	196,279	185,881
Above market leases [Member]
Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, Net
Finite-lived intangible assets/liabilities, gross	0	611
Accumulated amortization	0	(116)
Finite-lived intangible assets	0	495
In-place leases [Member]
Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, Net
Finite-lived intangible assets/liabilities, gross	40,323	58,076
Accumulated amortization	(25,653)	(31,647)
Finite-lived intangible assets	14,670	26,429
Below-market operating leases [Member]
Acquisition-related Intangible Liabilities, Net [Abstract]
Acquisition-related intangible liabilities, gross	26,405	51,263
Accumulated amortization	(13,060)	(27,171)
Acquisition-related intangible liabilities, net	$ 13,345	$ 24,092

Deferred Leasing Costs and Ac_4

Deferred Leasing Costs and Acquisition-Related Intangible Assets and Liabilities, net - Amortization of Deferred Leasing Costs and Acquisition-related Intangibles (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Amortization for the period related to deferred leasing costs and acquisition-related intangibles
Amortization for the period related to deferred leasing costs and acquisition-related intangibles	$ 35,130	$ 45,188	$ 40,415
Deferred leasing costs [Member]
Amortization for the period related to deferred leasing costs and acquisition-related intangibles
Amortization for the period related to deferred leasing costs and acquisition-related intangibles	33,624	35,779	34,341
Estimated annual amortization related to acquisition-related intangible assets
Finite-lived intangible assets, 2021	31,048
Finite-lived intangible assets, 2022	28,334
Finite-lived intangible assets, 2023	24,470
Finite-lived intangible assets, 2024	21,545
Finite-lived intangible assets, 2025	19,726
Finite-lived intangible assets, thereafter	71,156
Finite-lived intangible assets	196,279	185,881
Above market leases [Member]
Amortization for the period related to deferred leasing costs and acquisition-related intangibles
Amortization for the period related to deferred leasing costs and acquisition-related intangibles	495	192	444
Estimated annual amortization related to acquisition-related intangible assets
Finite-lived intangible assets	0	495
In-place leases [Member]
Amortization for the period related to deferred leasing costs and acquisition-related intangibles
Amortization for the period related to deferred leasing costs and acquisition-related intangibles	11,759	18,615	15,915
Estimated annual amortization related to acquisition-related intangible assets
Finite-lived intangible assets, 2021	6,531
Finite-lived intangible assets, 2022	3,885
Finite-lived intangible assets, 2023	1,534
Finite-lived intangible assets, 2024	584
Finite-lived intangible assets, 2025	473
Finite-lived intangible assets, thereafter	1,663
Finite-lived intangible assets	14,670	26,429
Below-market ground lease obligation [Member]
Amortization for the period related to deferred leasing costs and acquisition-related intangibles
Amortization for the period related to deferred leasing costs and acquisition-related intangibles	0	0	8
Below-market operating leases [Member]
Amortization for the period related to deferred leasing costs and acquisition-related intangibles
Amortization of intangible liabilities	(10,748)	(9,398)	(10,192)
Estimated annual amortization related to acquisition-related intangible liabilities
Acquisition-related intangible liabilities, 2021	(4,152)
Acquisition-related intangible liabilities, 2022	(3,167)
Acquisition-related intangible liabilities, 2023	(1,486)
Acquisition-related intangible liabilities, 2024	(812)
Acquisition-related intangible liabilities, 2025	(710)
Acquisition-related intangible liabilities, thereafter	(3,018)
Acquisition-related intangible liabilities	(13,345)	(24,092)
Above-market ground lease obligation [Member]
Amortization for the period related to deferred leasing costs and acquisition-related intangibles
Amortization of intangible liabilities	$ 0	$ 0	$ (101)

Receivables - Current Receivabl

Receivables - Current Receivables and Deferred Rent Receivables (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current Receivables, net
Current receivables	$ 13,806	$ 27,660
Allowance for uncollectible tenant receivables	(1,799)	(1,171)
Current receivables, net	12,007	26,489
Deferred Rent Receivables, net
Deferred rent receivables	387,462	339,489
Allowance for deferred rent receivables	(804)	(1,552)
Deferred rent receivables, net	$ 386,658	$ 337,937

Prepaid Expenses and Other As_3

Prepaid Expenses and Other Assets, Net - Schedule of Prepaid Expenses and Other Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Furniture, fixtures and other long-lived assets, net	$ 43,367	$ 35,286
Prepaid expenses	10,193	18,724
Notes receivable, net	0	1,651
Total prepaid expenses and other assets, net	$ 53,560	55,661
Non-refundable acquisition deposit		$ 3,600

Secured and Unsecured Debt of_4

Secured and Unsecured Debt of the Company - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Secured debt	$ 253,582	$ 258,593
Unsecured debt [Member]
Debt Instrument [Line Items]
Long-term debt	$ 3,700,000	$ 3,300,000

Secured and Unsecured Debt of_5

Secured and Unsecured Debt of the Operating Partnership - Secured Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Secured Debt
Secured debt	$ 253,582	$ 258,593
Kilroy Realty L.P. [Member]
Secured Debt
Long-term debt, gross	3,954,365
Secured debt	253,582	258,593
Unamortized Deferred Financing Costs	(22,400)
Kilroy Realty L.P. [Member] | Secured debt [Member]
Secured Debt
Secured debt	254,365	259,502
Unamortized Deferred Financing Costs	(783)	(909)
Long-term debt	253,582	258,593
Net book value of properties pledged as collateral for secured debt	$ 222,000
Kilroy Realty L.P. [Member] | Secured debt [Member] | 3.57% Mortgage Payable due December 2026 [Member]
Secured Debt
Stated interest rate	3.57%
Effective interest rate	3.57%
Long-term debt, gross	$ 166,776	170,000
Kilroy Realty L.P. [Member] | Secured debt [Member] | 4.48% Mortgage Payable due July 2027 [Member]
Secured Debt
Stated interest rate	4.48%
Effective interest rate	4.48%
Long-term debt, gross	$ 87,589	$ 89,502

Secured and Unsecured Debt of_6

Secured and Unsecured Debt of the Operating Partnership - Unsecured Senior Notes Table (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Aug. 31, 2020	Dec. 31, 2019	Sep. 30, 2019
Debt Instrument [Line Items]
Unsecured debt, net	$ 3,670,099		$ 3,049,185
Unsecured debt [Member]
Debt Instrument [Line Items]
Unamortized discount (premium), net	(8,300)		(6,500)
Unamortized debt issuance expense	21,600		18,700
Kilroy Realty L.P. [Member]
Debt Instrument [Line Items]
Unamortized debt issuance expense	22,400
Long-term debt, gross	3,954,365
Unsecured debt, net	3,670,099		3,049,185
Kilroy Realty L.P. [Member] | Unsecured debt [Member]
Debt Instrument [Line Items]
Unsecured debt, net	$ 3,670,099		2,899,839
Kilroy Realty L.P. [Member] | Unsecured debt [Member] | 2.500% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Unamortized discount (premium), net		$ (2,700)
Stated interest rate	2.50%
Effective interest rate	2.56%
Long-term debt, gross	$ 425,000		0
Unamortized discount and deferred financing costs	(6,332)		0
Unsecured debt, net	$ 418,668		0
Kilroy Realty L.P. [Member] | Unsecured debt [Member] | 4.270% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Stated interest rate	4.27%
Effective interest rate	4.27%
Long-term debt, gross	$ 350,000		0
Unamortized discount and deferred financing costs	(1,825)		0
Unsecured debt, net	$ 348,175		0
Kilroy Realty L.P. [Member] | Unsecured debt [Member] | 3.050% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Unamortized discount (premium), net				$ (600)
Stated interest rate	3.05%
Effective interest rate	3.064%
Long-term debt, gross	$ 500,000		500,000
Unamortized discount and deferred financing costs	(5,399)		(5,998)
Unsecured debt, net	$ 494,601		494,002
Kilroy Realty L.P. [Member] | Unsecured debt [Member] | 4.750% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Stated interest rate	4.75%
Effective interest rate	4.80%
Long-term debt, gross	$ 400,000		400,000
Unamortized discount and deferred financing costs	(3,952)		(4,446)
Unsecured debt, net	$ 396,048		395,554
Kilroy Realty L.P. [Member] | Unsecured debt [Member] | 4.350% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Stated interest rate	4.35%
Effective interest rate	4.35%
Long-term debt, gross	$ 200,000		200,000
Unamortized discount and deferred financing costs	(1,012)		(1,186)
Unsecured debt, net	$ 198,988		198,814
Kilroy Realty L.P. [Member] | Unsecured debt [Member] | 4.300% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Stated interest rate	4.30%
Effective interest rate	4.30%
Long-term debt, gross	$ 50,000		50,000
Unamortized discount and deferred financing costs	(246)		(290)
Unsecured debt, net	$ 49,754		49,710
Kilroy Realty L.P. [Member] | Unsecured debt [Member] | 3.450% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Stated interest rate	3.45%
Effective interest rate	3.47%
Long-term debt, gross	$ 425,000		425,000
Unamortized discount and deferred financing costs	(2,321)		(2,907)
Unsecured debt, net	$ 422,679		422,093
Kilroy Realty L.P. [Member] | Unsecured debt [Member] | 3.450% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Stated interest rate	3.45%
Effective interest rate	3.45%
Long-term debt, gross	$ 75,000		75,000
Unamortized discount and deferred financing costs	(347)		(390)
Unsecured debt, net	$ 74,653		74,610
Kilroy Realty L.P. [Member] | Unsecured debt [Member] | 3.350% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Stated interest rate	3.35%
Effective interest rate	3.35%
Long-term debt, gross	$ 175,000		175,000
Unamortized discount and deferred financing costs	(709)		(825)
Unsecured debt, net	$ 174,291		174,175
Kilroy Realty L.P. [Member] | Unsecured debt [Member] | 4.375% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Stated interest rate	4.375%
Effective interest rate	4.444%
Long-term debt, gross	$ 400,000		400,000
Unamortized discount and deferred financing costs	(2,631)		(3,185)
Unsecured debt, net	$ 397,369		396,815
Kilroy Realty L.P. [Member] | Unsecured debt [Member] | 4.250% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Stated interest rate	4.25%
Effective interest rate	4.35%
Long-term debt, gross	$ 400,000		400,000
Unamortized discount and deferred financing costs	(4,567)		(5,100)
Unsecured debt, net	$ 395,433		394,900
Kilroy Realty L.P. [Member] | Unsecured debt [Member] | 3.800% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Stated interest rate	3.80%
Effective interest rate	3.80%
Long-term debt, gross	$ 300,000		300,000
Unamortized discount and deferred financing costs	(560)		(834)
Unsecured debt, net	$ 299,440		$ 299,166

Secured and Unsecured Debt of_7

Secured and Unsecured Debt of the Operating Partnership - Unsecured Senior Notes - Registered Offerings and Private Placement (Details) - USD ($)	1 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Aug. 31, 2020	Apr. 30, 2020	Sep. 30, 2019
Debt Instrument [Line Items]
Proceeds from issuance of unsecured debt		$ 772,297,000	$ 499,390,000	$ 648,537,000
Loss on early extinguishment of debt (Note 9)		0	0	12,623,000
Unsecured debt [Member]
Debt Instrument [Line Items]
Unamortized discount (premium), net		(8,300,000)	(6,500,000)
Kilroy Realty L.P. [Member]
Debt Instrument [Line Items]
Proceeds from issuance of unsecured debt		772,297,000	499,390,000	648,537,000
Loss on early extinguishment of debt (Note 9)		$ 0	$ 0	$ 12,623,000
Kilroy Realty L.P. [Member] | Unsecured debt [Member] | 2.500% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Principal amount					$ 425,000,000
Unamortized discount (premium), net					$ (2,700,000)
Stated interest rate		2.50%
Kilroy Realty L.P. [Member] | Unsecured debt [Member] | 3.050% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Principal amount							$ 500,000,000
Unamortized discount (premium), net							$ (600,000)
Stated interest rate		3.05%
Kilroy Realty L.P. [Member] | Unsecured debt [Member] | 4.750% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Stated interest rate		4.75%
Kilroy Realty L.P. [Member] | Unsecured debt [Member] | 6.625% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Stated interest rate	6.625%			6.625%
Extinguishment of debt	$ 250,000,000
Loss on early extinguishment of debt (Note 9)	12,600,000
Premium paid to the note holders at the redemption date	11,800,000
Write-off of unamortized discount and unamortized deferred financing costs	$ 800,000
Kilroy Realty L.P. [Member] | Unsecured debt [Member] | 4.270% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Principal amount						$ 350,000,000
Stated interest rate		4.27%

Secured and Unsecured Debt of_8

Secured and Unsecured Debt of the Operating Partnership - Unsecured Revolving Credit Facility and Term Loan Facility (Details) - USD ($)	1 Months Ended	12 Months Ended
	Aug. 31, 2020	Dec. 31, 2020	Dec. 31, 2019
Terms of the Credit Facility
Outstanding borrowings		$ 0	$ 245,000,000
Kilroy Realty L.P. [Member]
Terms of the Credit Facility
Outstanding borrowings		0	245,000,000
Unamortized debt issuance expense		22,400,000
Kilroy Realty L.P. [Member] | Revolving credit facility [Member]
Terms of the Credit Facility
Outstanding borrowings		0	245,000,000
Remaining borrowing capacity		750,000,000	505,000,000
Total borrowing capacity		$ 750,000,000	$ 750,000,000
Interest rate		1.14%	2.76%
Facility fee-annual rate		0.20%
Contingent additional borrowings		$ 600,000,000
Unamortized debt issuance expense		$ 2,100,000	$ 3,400,000
Kilroy Realty L.P. [Member] | Line of credit [Member]
Terms of the Credit Facility
Total borrowing capacity			150,000,000
Kilroy Realty L.P. [Member] | $150.0 million term loan facility [Member] | Line of credit [Member]
Terms of the Credit Facility
Extinguishment of debt	$ 150,000,000
Outstanding borrowings			150,000,000
Remaining borrowing capacity			$ 0
Interest rate			2.85%
Undrawn facility fee-annual rate			0.20%
Unamortized debt issuance expense			$ 700,000
Kilroy Realty L.P. [Member] | London Interbank Offered Rate (LIBOR) [Member] | Revolving credit facility [Member]
Terms of the Credit Facility
Basis spread on LIBOR		1.00%	1.00%
Kilroy Realty L.P. [Member] | London Interbank Offered Rate (LIBOR) [Member] | $150.0 million term loan facility [Member] | Line of credit [Member]
Terms of the Credit Facility
Basis spread on LIBOR			1.10%

Secured and Unsecured Debt of_9

Secured and Unsecured Debt of the Operating Partnership - Debt Maturities (Details) - Kilroy Realty L.P. [Member] $ in Thousands	Dec. 31, 2020USD ($)
Stated debt maturities and scheduled amortization payments, excluding debt discounts
2021	$ 5,342
2022	5,554
2023	305,775
2024	431,006
2025	406,246
Thereafter	2,800,442
Total aggregate principal value	3,954,365
Unamortized debt issuance expense	(22,400)
Unsecured senior notes [Member]
Stated debt maturities and scheduled amortization payments, excluding debt discounts
Debt issuance discount	$ (8,300)

Secured and Unsecured Debt o_10

Secured and Unsecured Debt of the Operating Partnership - Capitalized Interest and Loan Fees (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Interest expense	$ 70,772	$ 48,537	$ 49,721
Kilroy Realty L.P. [Member]
Debt Instrument [Line Items]
Gross interest expense	150,325	129,778	117,789
Capitalized interest and deferred financing costs	(79,553)	(81,241)	(68,068)
Interest expense	$ 70,772	$ 48,537	$ 49,721

Deferred Revenue and Acquisit_3

Deferred Revenue and Acquisition-Related Intangible Liabilities, net - Deferred Revenue and Acquisition-Related Intangible Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Deferred revenue	$ 88,645	$ 96,271
Other deferred revenue	26,533	19,125
Acquisition-related intangible liabilities, net	13,345	24,092
Deferred revenue and acquisition-related intangible liabilities, net	$ 128,523	$ 139,488

Deferred Revenue and Acquisit_4

Deferred Revenue and Acquisition-Related Intangible Liabilities, net - Estimated Amortization of Deferred Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Deferred Revenue, Future Amortization Recognized By Year [Abstract]
Total	$ 88,645	$ 96,271
Tenant funded tenant improvements [Member]
Deferred Revenue Arrangement [Line Items]
Deferred revenues amortized and recognized as rental income	22,500	$ 19,200	$ 18,400
Deferred Revenue, Future Amortization Recognized By Year [Abstract]
2021	16,216
2022	15,188
2023	13,367
2024	11,325
2025	8,564
Thereafter	23,985
Total	$ 88,645

Noncontrolling Interests on t_3

Noncontrolling Interests on the Company’s Consolidated Financial Statements - Narrative (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)d$ / sharesshares	Dec. 31, 2019USD ($)$ / sharesshares	Dec. 31, 2018shares
Noncontrolling Interest [Line Items]
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	$ 65,400	$ 167,700
Noncontrolling interest in consolidated subsidiary	$ 197,503	$ 195,431
Common units [Member] | Kilroy Realty L.P. [Member]
Noncontrolling Interest [Line Items]
Common units outstanding held by common limited partners (in units) | shares	1,150,574	2,023,287
Conversion ratio	1
Common Stock [Member]
Noncontrolling Interest [Line Items]
Exchange of common units of the Operating Partnership (in units) | shares	872,713	2,000	51,906
Operating Partnership [Member]
Noncontrolling Interest [Line Items]
Ownership interest	99.00%	98.10%
Non-affiliated Investors and Certain Executive Officersand Directors of the Company [Member]
Noncontrolling Interest [Line Items]
Ownership interest of noncontrolling interest	1.00%	1.90%
101 First LLC and 303 Second LLC [Member]
Noncontrolling Interest [Line Items]
Ownership interest	56.00%
101 First LLC and 303 Second LLC [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Noncontrolling Interest [Line Items]
Noncontrolling interest in consolidated subsidiary	$ 191,900	$ 189,600
Redwood LLC [Member]
Noncontrolling Interest [Line Items]
Ownership interest	93.00%
Noncontrolling interest in consolidated subsidiary	$ 5,600	$ 5,800

Noncontrolling Interests on t_4

Noncontrolling Interests on the Operating Partnership’s Consolidated Financial Statements - Narrative (Details)	Aug. 30, 2016
Consolidated property partnerships [Member] | Norges Bank Real Estate Management (NBREM) [Member]
Noncontrolling Interest [Line Items]
Ownership interest of noncontrolling interest	44.00%

Stockholders' Equity of the C_3

Stockholders' Equity of the Company - Narrative (Details) - USD ($)	Mar. 25, 2020	Feb. 18, 2020	Mar. 31, 2020	Jul. 31, 2019	Aug. 31, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	May 19, 2020	May 18, 2020	Jun. 30, 2018
Class of Stock [Line Items]
Common stock, authorized (shares)						280,000,000	150,000,000		280,000,000	150,000,000
Common stock, value, issued						$ 1,160,000	$ 1,060,000
Aggregate net proceeds after selling commissions						$ 721,665,000	$ 353,722,000	$ 130,693,000
Sale of stock, shares issued (in shares)						116,035,827	106,016,287
Stock repurchase program, number of shares authorized to be repurchased						4,935,826
Stock repurchased during period (in shares)						0	0	0
2014 At-The-Market Program [Member]
Class of Stock [Line Items]
Aggregate gross proceeds								$ 300,000,000
2018 At-The-Market Program [Member]
Class of Stock [Line Items]
Aggregate gross proceeds											$ 500,000,000
Issuance of Equity under ATM Program [Member]
Class of Stock [Line Items]
Aggregate net proceeds after selling commissions						$ 247,300,000		132,100,000
Aggregate gross proceeds						$ 252,000,000		$ 133,800,000
Shares issued, price per share (in dollars per share)						$ 80.08		$ 73.64
Forward Equity Offering [Member]
Class of Stock [Line Items]
Common stock, value, issued		$ 494,500,000			$ 360,500,000
Stock issued, price per share (in dollar per share)		$ 86			$ 72.10
Aggregate net proceeds after selling commissions				$ 354,300,000
Forward Equity Offering [Member] | Common Stock [Member]
Class of Stock [Line Items]
Stock issued (in shares)		5,750,000		5,000,000	5,000,000
Aggregate net proceeds after selling commissions	$ 474,900,000			$ 354,300,000
Sale of stock, shares issued (in shares)	5,750,000		5,750,000	5,000,000
Forward Equity Offering [Member] | Common Stock [Member] | 2014 At-The-Market Program [Member]
Class of Stock [Line Items]
Sale of stock, shares available for sale (in shares)								1,369,729
Forward Equity Offering [Member] | Common Stock [Member] | 2018 At-The-Market Program [Member]
Class of Stock [Line Items]
Stock issued, price per share (in dollar per share)							$ 80.08
Sale of stock, shares available for sale (in shares)							3,147,110	447,466
Sale of stock, shares issued (in shares)						3,594,576
Sale of stock, available for sale under program						$ 214,200,000
Forward Equity Offering [Member] | Common Stock [Member] | Issuance of Equity under ATM Program [Member]
Class of Stock [Line Items]
Aggregate net proceeds after selling commissions			$ 247,300,000			$ 247,300,000
Sale of stock, shares issued (in shares)			3,147,110

Stockholders' Equity of the C_4

Stockholders' Equity of the Company - At-The-Market Offering and Derivatives and Distributions (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Dividends Payable [Line Items]
Aggregate net proceeds after selling commissions	$ 721,665	$ 353,722	$ 130,693
Accrued dividend and distributions
Accrued dividends and distributions	$ 59,431	$ 53,219
Summary of shares and units
Common stock	116,035,827	106,016,287
Restricted Stock Units (RSUs) [Member]
Summary of shares and units
RSUs	1,638,026	1,651,905
Common stockholders and noncontrolling unitholders [Member]
Accrued dividend and distributions
Accrued dividends and distributions	$ 59,431	$ 53,219
Common Stock [Member]
Accrued dividend and distributions
Accrued dividends and distributions	$ 58,018	$ 51,418
Summary of shares and units
Common stock	116,035,827	106,016,287
Common units [Member]
Accrued dividend and distributions
Accrued dividends and distributions	$ 575	$ 981
Issuance of Equity under ATM Program [Member]
Dividends Payable [Line Items]
Shares of common stock sold during the period (in shares)	3,147,110		1,817,195
Weighted average price per share of common stock (in dollars per share)	$ 80.08		$ 73.64
Aggregate gross proceeds	$ 252,000		$ 133,800
Aggregate net proceeds after selling commissions	247,300		132,100
Kilroy Realty L.P. [Member]
Dividends Payable [Line Items]
Aggregate net proceeds after selling commissions	721,665	353,722	$ 130,693
Accrued dividend and distributions
Accrued dividends and distributions	59,431	53,219
Kilroy Realty L.P. [Member] | Restricted Stock Units (RSUs) [Member]
Accrued dividend and distributions
Accrued dividends and distributions	$ 838	$ 820
Kilroy Realty L.P. [Member] | Market measure-based Restricted Stock Units (RSUs) [Member]
Summary of shares and units
Number of RSUs outstanding (in shares)	873,709	932,675
Kilroy Realty L.P. [Member] | Common units [Member]
Summary of shares and units
Noncontrolling common units (in units)	1,150,574	2,023,287

Partners' Capital of the Oper_3

Partners' Capital of the Operating Partnership - Narrative (Details) - USD ($) $ in Thousands	Mar. 25, 2020	Jul. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Mar. 31, 2020
Class of Stock [Line Items]
Common stock, shares issued (in shares)			116,035,827	106,016,287
Aggregate net proceeds after selling commissions			$ 721,665	$ 353,722	$ 130,693
Forward Equity Sale [Member]
Class of Stock [Line Items]
Aggregate net proceeds after selling commissions		$ 354,300
Forward Equity Sale [Member] | Common Stock [Member]
Class of Stock [Line Items]
Common stock, shares issued (in shares)	5,750,000	5,000,000				5,750,000
Aggregate net proceeds after selling commissions	$ 474,900	$ 354,300
Common units (in units)		5,000,000				5,750,000

Partners' Capital of the Oper_4

Partners' Capital of the Operating Partnership - At-The-Market Stock Offering, Common Units and Accrued Distributions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Class of Stock [Line Items]
Aggregate net proceeds after selling commissions	$ 721,665	$ 353,722	$ 130,693
Accrued distributions
Accrued dividends and distributions	59,431	53,219
Common units [Member]
Accrued distributions
Accrued dividends and distributions	$ 575	981
Issuance of Equity under ATM Program [Member]
Class of Stock [Line Items]
Shares of common stock contributed by the Company (in shares)	3,147,110		1,817,195
Common units exchanged for shares of common stock by the Company (in units)	3,147,110		1,817,195
Aggregate gross proceeds	$ 252,000		$ 133,800
Aggregate net proceeds after selling commissions	247,300		132,100
Kilroy Realty L.P. [Member]
Class of Stock [Line Items]
Aggregate net proceeds after selling commissions	721,665	353,722	$ 130,693
Accrued distributions
Accrued dividends and distributions	59,431	53,219
Kilroy Realty L.P. [Member] | Restricted Stock Units (RSUs) [Member]
Accrued distributions
Accrued dividends and distributions	$ 838	$ 820
RSUs (in shares)	1,638,026	1,651,905
Kilroy Realty L.P. [Member] | Market measure-based Restricted Stock Units (RSUs) [Member]
Accrued distributions
Number of RSUs outstanding (in shares)	873,709	932,675
Kilroy Realty L.P. [Member] | Partners Capital Common Unit [Member]
Accrued distributions
Accrued dividends and distributions	$ 59,431	$ 53,219
Kilroy Realty L.P. [Member] | Partners capital general partner [Member]
Accrued distributions
Accrued dividends and distributions	58,018	51,418
Kilroy Realty L.P. [Member] | Partners capital limited partner [Member]
Accrued distributions
Accrued dividends and distributions	$ 575	$ 981
Kilroy Realty L.P. [Member] | Common units [Member]
Summary of units
Company owned common units in the Operating Partnership (in units)	116,035,827	106,016,287
Noncontrolling common units (in units)	1,150,574	2,023,287
Operating Partnership [Member]
Summary of units
Company owned general partnership interest	99.00%	98.10%
Operating Partnership [Member] | Non-Affiliated Investors [Member]
Summary of units
Ownership interest of noncontrolling interest	1.00%	1.90%

Share-Based and Other Compens_3

Share-Based and Other Compensation - Stockholder Approved Share-Based Incentive Compensation Plan (Details) shares in Millions	Dec. 31, 2020shares
Kilroy Realty 2006 Incentive Award Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, number of shares available for grant	1.5
Shareholder Meeting Date May 21, 2015 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, number of shares requested	10.7

Share-Based and Other Compens_4

Share-Based and Other Compensation - Share-Based Compensation Grants (Details) - shares	Jan. 31, 2020	Feb. 01, 2019	Dec. 27, 2018	Feb. 14, 2018	Jan. 31, 2020	Feb. 28, 2019	Dec. 31, 2018	Feb. 28, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in period (in shares)					263,626
Restricted Stock Units (RSUs) [Member] | Executive officer share-based compensation programs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in period (in shares)			161,290			288,378		282,038
Restricted Stock Units (RSUs) [Member] | Chief Executive Officer [Member] | Executive officer share-based compensation programs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in period (in shares)			483,871
Market measure-based Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in period (in shares)					154,267
Market measure-based Restricted Stock Units (RSUs) [Member] | Executive officer share-based compensation programs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in period (in shares)	154,267	143,396	80,647	158,205
Market measure-based Restricted Stock Units (RSUs) [Member] | Chief Executive Officer [Member] | Executive officer share-based compensation programs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in period (in shares)			266,130
Time-Based Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in period (in shares)					109,359
Time-Based Restricted Stock Units (RSUs) [Member] | Executive officer share-based compensation programs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in period (in shares)			80,643			144,982		123,833			14,999
Forfeited in period (in shares)									5,148	10,733
Time-Based Restricted Stock Units (RSUs) [Member] | Chief Executive Officer [Member] | Executive officer share-based compensation programs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in period (in shares)			217,741
Performance-Based RSUs [Member] | Executive officer share-based compensation programs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Forfeited in period (in shares)									12,263	24,353
December 2018 Market-Based RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in period (in shares)							346,777
December 2018 Market-Based RSUs [Member] | Executive officer share-based compensation programs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in period (in shares)						143,396		158,205
Time-Based Restricted Stock Units (RSUs), 2018 Special Time-Based RSU Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in period (in shares)			298,384
Time-Based Restricted Stock Units (RSUs), 2018 Special Time-Based RSU Grant [Member] | Executive officer share-based compensation programs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Forfeited in period (in shares)									6,441	98,844

Share-Based and Other Compens_5

Share-Based and Other Compensation - 2018 Special Market-Based RSU Grant (Details) - USD ($) $ / shares in Units, $ in Millions	Dec. 27, 2018	Dec. 31, 2018
December 2018 Market-Based RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in period (in shares)		346,777
Award vesting period		3 years
Vesting criteria, one (percent)		75.00%
Vesting criteria, two (percent)		25.00%
Fair value RSUs granted	$ 23.8
Fair value per share on valuation date (in dollars per share)	$ 68.66
Expected share price volatility (in dollars per share)	23.00%
Risk-free interest rate	2.40%
December 2018 Market-Based RSUs, TSR [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period		4 years
Minimum [Member] | December 2018 Market-Based RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Target percent		0.00%
Maximum [Member] | December 2018 Market-Based RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Target percent		200.00%

Share-Based and Other Compens_6

Share-Based and Other Compensation - Annual Performance-Based RSU Grants (Details) - USD ($) $ / shares in Units, $ in Millions	Jan. 31, 2020	Feb. 01, 2019	Dec. 27, 2018	Feb. 14, 2018	Jan. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Performance-Based RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period						3 years	3 years	3 years
Vesting criteria, one (percent)						100.00%	100.00%	100.00%
Vesting criteria, two (percent)						50.00%	50.00%	50.00%
Vesting criteria, three (percent)						50.00%	50.00%	50.00%
Performance-based RSUs achievement target, participant one, percent						100.00%	175.00%	219.00%
Performance-based RSUs achievement target, all other participants, percent							150.00%	175.00%
Fair value RSUs granted	$ 12.9	$ 10.2		$ 10.8
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Fair value per share on valuation date (in dollars per share)	$ 84.54
Expected share price volatility (in dollars per share)	17.00%
Risk-free interest rate	1.35%
2019 Performance-Based RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Fair value per share on valuation date (in dollars per share)		$ 72.57
2018 Performance-Based RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Fair value per share on valuation date (in dollars per share)				$ 70.08
Expected share price volatility (in dollars per share)		19.00%		20.00%
Risk-free interest rate		2.48%		2.37%
Market measure-based Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in period (in shares)					154,267
Estimated RSUs earned based on FFO (in shares)	142,004				142,004
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Fair value per share on valuation date (in dollars per share)						$ 85.08
Executive officer share-based compensation programs [Member] | Market measure-based Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in period (in shares)	154,267	143,396	80,647	158,205
Market measure-based RSU estimate of probable [Member] | Performance-Based RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Estimated RSUs earned based on FFO (in shares)						142,004
Target level of achievement, one (percent)						100.00%
Market measure-based RSU estimate of probable [Member] | 2019 Performance-Based RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Estimated RSUs earned based on FFO (in shares)						220,151
Market measure-based RSU estimate of probable [Member] | Market measure-based Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Estimated RSUs earned based on FFO (in shares)		220,151		229,748

Share-Based and Other Compens_7

Share-Based and Other Compensation - Annual Time-Based RSU Grants (Details) $ / shares in Units, $ in Millions	Jan. 31, 2020property$ / shares	Feb. 01, 2019USD ($)property$ / shares	Dec. 27, 2018USD ($)$ / shares	Feb. 14, 2018$ / sharesshares	Jan. 29, 2018$ / sharesshares	Jan. 31, 2020USD ($)$ / shares	Feb. 28, 2018USD ($)propertyparticipant	Dec. 31, 2020shares	Dec. 31, 2018
Time-Based Restricted Stock Units (RSUs), 2020 Time-Based RSU Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of equal annual vesting installments | property	3
Fair value RSUs granted | $						$ 9
Fair value per share (in dollars per share) | $ / shares	$ 82.57					$ 82.57
Time-Based Restricted Stock Units (RSUs), 2019 Time-Based RSU Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of equal annual vesting installments | property		3
Fair value RSUs granted | $		$ 10.1
Fair value per share (in dollars per share) | $ / shares		$ 69.89
December 2018 Time-Based RSU Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting criteria, one (percent)									50.00%
Vesting criteria, two (percent)									50.00%
Fair value RSUs granted | $			$ 18.5
Fair value per share (in dollars per share) | $ / shares			$ 62
Time-Based Restricted Stock Units (RSUs), 2018 Time-Based RSU Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of equal annual vesting installments | property							3
Number of participants with shorter service period | participant							1
Fair value RSUs granted | $							$ 8.4
Fair value per share (in dollars per share) | $ / shares				$ 66.46	$ 70.37
RSUs granted (in units) | shares				67,818	56,015
Time-Based Restricted Stock Units (RSUs) with Accelerated Vesting due to Separation of Employment [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSUs (in shares) | shares								54,735

Share-Based and Other Compens_8

Share-Based and Other Compensation - Summary of Market-Measure Based RSUs (Details) - $ / shares	1 Months Ended	12 Months Ended
	Jan. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Award vesting period		3 years
Market measure-based Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Granted (in shares)	154,267
Vested (in shares)		(270,054)	(265,737)	(265,918)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
RSU weighted average fair value, beginning balance (in dollars per share)	$ 71.04	$ 71.04
Fair value per share on valuation date (in dollars per share)		85.08
Weighted average grant date fair value, vested (in dollars per share)		74.71
Weighted average fair value, issuance of dividend equivalents (in dollars per share)		62.21
Weighted average fair value, forfeited (in dollars per share)		84.54
RSU weighted average fair value, ending balance (in dollars per share)		$ 72.06	$ 71.04
Market measure-based Restricted Stock Units (RSUs) [Member] | Nonvested Restricted Stock Units RSU [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Number of RSUs outstanding, beginning balance (in shares)	932,675	932,675
Granted (in shares)		154,267	231,191	601,012
Vested (in shares)		(230,334)
Issuance of dividend equivalents (in shares)		29,561
Forfeited (in shares)		(12,460)
Number of RSUs outstanding, ending balance (in shares)		873,709	932,675
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Fair value per share on valuation date (in dollars per share)		$ 85.08	$ 71.12	$ 68.51
Market measure-based Restricted Stock Units (RSUs) [Member] | Vested Restricted Stock Units R S U [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Vested RSUs, beginning balance (in shares)	36,679	36,679
Granted (in shares)		38,313
Vested (in shares)		(230,334)
Settled (in shares)		(259,954)
Issuance of dividend equivalents (in shares)		1,407
Forfeited (in shares)		(4)
Vested RSUs, ending balance (in shares)		46,775	36,679
Market measure-based Restricted Stock Units (RSUs) [Member] | Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Total RSUs, beginning balance (in shares)	969,354	969,354
Granted (in shares)		192,580
Vested (in shares)		0
Settled (in shares)		(259,954)
Issuance of dividend equivalents (in shares)		30,968
Forfeited (in shares)		(12,464)
Total RSUs, ending balance (in shares)		920,484	969,354
Kilroy Realty 2006 Incentive Award Plan [Member] | Market measure-based Restricted Stock Units (RSUs) [Member] | Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Settled (in shares)		(125,928)

Share-Based and Other Compens_9

Share-Based and Other Compensation - Market-Measure Based RSUs (Details) - Market measure-based Restricted Stock Units (RSUs) [Member] - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Jan. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	154,267
Fair value per share on valuation date (in dollars per share)		$ 85.08
Vested (in shares)		(270,054)	(265,737)	(265,918)
Nonvested Restricted Stock Units RSU [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)		154,267	231,191	601,012
Fair value per share on valuation date (in dollars per share)		$ 85.08	$ 71.12	$ 68.51
Vested (in shares)		(230,334)
Vested Restricted Stock Units RSU [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)		38,313
Vested (in shares)		(230,334)
Total Fair Value at Vest Date		$ 19,471	$ 18,703	$ 18,906

Share-Based and Other Compen_10

Share-Based and Other Compensation - Summary of Time-Based RSUs (Details) - Time-Based Restricted Stock Units (RSUs) [Member] - $ / shares	1 Months Ended	12 Months Ended
	Jan. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Granted (in shares)	109,359
Vested (in shares)		208,608	182,219	214,131
Nonvested Restricted Stock Units RSU [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Number of RSUs outstanding, beginning balance (in shares)	543,848	543,848
Granted (in shares)		120,769	153,005	437,216
Vested (in shares)		173,796
Issuance of dividend equivalents (in shares)		15,523
Forfeited (in shares)		(11,979)
Number of RSUs outstanding, ending balance (in shares)		494,365	543,848
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
RSU weighted average fair value, beginning balance (in dollars per share)	$ 66.66	$ 66.66
Fair value per share on valuation date (in dollars per share)		79.74	$ 70.31	$ 64.21
Weighted average grant date fair value, vested (in dollars per share)		70.83
Weighted average fair value, issuance of dividend equivalents (in dollars per share)		61.80
Weighted average fair value, forfeited (in dollars per share)		77.58
RSU weighted average fair value, ending balance (in dollars per share)		$ 67.97	$ 66.66
Vested Restricted Stock Units RSU [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Vested RSUs, beginning balance (in shares)	1,071,378	1,071,378
Granted (in shares)		0
Vested (in shares)		173,796
Settled (in shares)		(181,462)
Issuance of dividend equivalents (in shares)		34,812
Forfeited (in shares)		0
Canceled (in shares)		(1,638)
Vested RSUs, ending balance (in shares)		1,096,886	1,071,378
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Total RSUs, beginning balance (in shares)	1,615,226	1,615,226
Granted (in shares)		120,769
Vested (in shares)		0
Settled (in shares)		(181,462)
Issuance of dividend equivalents (in shares)		50,335
Forfeited (in shares)		(11,979)
Canceled (in shares)		(1,638)
Total RSUs, ending balance (in shares)		1,591,251	1,615,226
Kilroy Realty 2006 Incentive Award Plan [Member] | Vested Restricted Stock Units RSU [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Settled (in shares)		(67,316)

Share-Based and Other Compen_11

Share-Based and Other Compensation - Time-Based RSUs (Details) - Time-Based Restricted Stock Units (RSUs) [Member] - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Jan. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	109,359
Vested (in shares)		(208,608)	(182,219)	(214,131)
Nonvested Restricted Stock Units RSU [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)		120,769	153,005	437,216
Fair value per share on valuation date (in dollars per share)		$ 79.74	$ 70.31	$ 64.21
Vested (in shares)		(173,796)
Vested Restricted Stock Units RSU [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)		0
Vested (in shares)		(173,796)
Total Fair Value at Vest Date		$ 15,066	$ 12,227	$ 14,768

Share-Based and Other Compen_12

Share-Based and Other Compensation - Time-Based Restricted Stock Unit Activity (Details) - Time-Based Restricted Stock Units (RSUs) [Member] - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Jan. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	109,359
Vested (in shares)		(208,608)	(182,219)	(214,131)
Nonvested Restricted Stock Units RSU [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)		120,769	153,005	437,216
Fair value per share on valuation date (in dollars per share)		$ 79.74	$ 70.31	$ 64.21
Vested (in shares)		(173,796)
Vested Restricted Stock Units RSU [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)		0
Vested (in shares)		(173,796)
Total Fair Value at Vest Date		$ 15,066	$ 12,227	$ 14,768

Share-Based and Other Compen_13

Share-Based and Other Compensation - Nonvested Restricted Stock (Details) - Restricted Stock [Member] $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)$ / sharesshares
Nonvested Restricted Stock Units RSU [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	0
Fair value per share on valuation date (in dollars per share) | $ / shares	$ 0
Vested Restricted Stock Units RSU [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vested (in shares)	(22,884)
Total Fair Value at Vest Date | $	$ 1,652

Share-Based and Other Compen_14

Share-Based and Other Compensation - Share-Based Compensation Cost Recorded During the Period and Other Compensation (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 27, 2018USD ($)age
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	$ 37.6	$ 32.8	$ 35.9
Share-based compensation costs	7.4	5.8	8
Unrecognized compensation costs	$ 35.1
Cost not yet recognized, period for recognition	1 year 4 months 24 days
General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Severance costs	$ 14.1
Severance [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	4.5
Chief Executive Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash retirement benefit, scenario one				$ 13.2
Cash retirement benefit, scenario two				$ 16.2
Retirement age | age				73
Compensation expense	$ 1.5	$ 1.5	$ 12.1

Employee Benefit Plans - Narrat

Employee Benefit Plans - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2007
Retirement Benefits [Abstract]
Eligibility period for 401K savings plan, period	3 months
401(k) plan, maximum participant deferral percent	60.00%
401(k) plan, employer match per dollar of participant contribution	$ 0.50
401(k) plan, maximum employer match percentage	10.00%
401(k) plan, contributions made	$ 1,600,000	$ 1,600,000	$ 1,500,000
Deferred Compensation, maximum participant deferral percent				70.00%
Deferred Compensation, maximum director fees and bonuses that may be deferred (percent)				100.00%
Deferred Compensation, mandatory Company contributions as percentage of gross monthly salary (percent)				10.00%
Deferred Compensation, liability under Plan	$ 27,400,000	$ 27,000,000

Rental Income and Future Mini_3

Rental Income and Future Minimum Rent - Allocation of Rental Income (Details) - USD ($) $ in Thousands	Jan. 01, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Leases [Abstract]
Fixed lease payments		$ 786,860	$ 708,362
Variable lease payments		124,443	115,915
Net collectability (reversals) recoveries		(18,997)	2,195
Total rental income		892,306	$ 826,472	$ 656,631
Write-off or revenue, as a result of the COVID-19 pandemic		18,400
Allowance for doubtful accounts, as a result of the COVID-19 pandemic		$ 600
Net collectability (reversals), transitioned to a cash basis of reporting	$ 2,200

Rental Income and Future Mini_4

Rental Income and Future Minimum Rent - Future Contractual Minimum Rent (Details) $ in Thousands	Dec. 31, 2020USD ($)
Future contractual minimum rent under operating lease
2021	$ 731,169
2022	804,488
2023	788,214
2024	750,051
2025	719,274
Thereafter	3,455,201
Total	$ 7,248,397

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)ground_lease	Dec. 31, 2019USD ($)
Long-term Purchase Commitment [Line Items]
Commitments for contracts and executed leases, operating and redevelopment and development properties	$ 614.9
Weighted average discount rate	5.11%
Weighted average remaining lease term	54 years
Variable lease, cost	$ 3	$ 2.9
Period after which ground lease rentals are adjusted based on fair market value and the Consumer Price Index	5 years
Annual ground lease rental obligations limit	$ 1
Duration of ground lease prior to increase five years	five years
Average annual percentage rent for previous five years (percent)	50.00%
Duration of ground lease prior to increase ten years	10 years
Average annual percentage rent for previous ten years (percent)	60.00%
Ground lease fixed ground rent increase, percent	5.00%
Ten year ground lease extension option [Member]
Long-term Purchase Commitment [Line Items]
Number of extension options | ground_lease	3
Ground lease extension option term	10 years
Forty-five year ground lease extension option [Member]
Long-term Purchase Commitment [Line Items]
Number of extension options | ground_lease	1
Ground lease extension option term	45 years
Environmental matters [Member]
Long-term Purchase Commitment [Line Items]
Accrued environmental remediation liabilities	$ 71.3	$ 80.7

Commitments and Contingencies_2

Commitments and Contingencies - Minimum Commitment Under Ground Leases (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2019
Minimum commitment under our ground leases
2021	$ 5,641
2022	5,642
2023	5,662
2024	5,662
2025	5,662
Thereafter	280,723
Total	308,992
Present value discount	(211,214)
Ground lease liabilities	$ 97,778	$ 98,400	$ 98,349

Fair Value Measurements and D_3

Fair Value Measurements and Disclosures - Assets and Liabilities Reported at Fair Value (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Fair value adjustment of marketable securities and deferred compensation plan liability
Net gain (loss) on marketable securities	$ 2,864	$ 3,885	$ (1,851)
Fair value, measurements, recurring [Member] | Fair Value (Level 1) [Member]
Assets and Liabilities Reported at Fair Value
Marketable securities	$ 27,481	$ 27,098

Fair Value Measurements and D_4

Fair Value Measurements and Disclosures - Financial Instruments Disclosed at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Carrying value [Member] | Secured debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt instrument, fair value disclosure	$ 253,582	$ 258,593
Carrying value [Member] | Unsecured debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt instrument, fair value disclosure	3,670,099	3,049,185
Carrying value [Member] | Unsecured line of credit [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt instrument, fair value disclosure	0	245,000
Fair value [Member] | Secured debt [Member] | Fair value (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt instrument, fair value disclosure	282,559	272,997
Fair value [Member] | Unsecured debt [Member] | Fair value (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt instrument, fair value disclosure	4,089,339	3,252,217
Fair value [Member] | Unsecured line of credit [Member] | Fair value (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt instrument, fair value disclosure	$ 0	$ 245,195

Net Income Available to Commo_5

Net Income Available to Common Stockholders Per Share of the Company - Basic and Diluted Net Income Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Numerator:
Net income attributable to common stockholders									$ 187,105	$ 195,443	$ 258,415
Allocation to participating securities									(2,229)	(2,119)	(2,004)
Numerator for basic and diluted net income available to common stockholders									$ 184,876	$ 193,324	$ 256,411
Denominator:
Basic weighted average vested shares/units outstanding (in shares/units)									113,241,341	103,200,568	99,972,359
Effect of dilutive securities (in shares)									478,281	648,600	510,006
Diluted weighted average vested shares and common stock/ unit equivalents outstanding (in shares/units)									113,719,622	103,849,168	100,482,365
Basic earnings per share:
Net income available to common stockholders per share - basic (in dollars per share)	$ 0.67	$ 0.42	$ 0.17	$ 0.37	$ 0.68	$ 0.41	$ 0.41	$ 0.36	$ 1.63	$ 1.87	$ 2.56
Diluted earnings per share:
Net income available to common stockholders per share - diluted (in dollars per share)	$ 0.67	$ 0.42	$ 0.17	$ 0.37	$ 0.67	$ 0.41	$ 0.41	$ 0.36	$ 1.63	$ 1.86	$ 2.55

Net Income Available to Commo_6

Net Income Available to Common Unitholders Per Unit of the Operating Partnership - Basic and Diluted Net Income Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Numerator:
Net income attributable to common unitholders									$ 187,105	$ 195,443	$ 258,415
Allocation to participating securities									(2,229)	(2,119)	(2,004)
Numerator for basic and diluted net income available to common stockholders									$ 184,876	$ 193,324	$ 256,411
Denominator:
Basic weighted average vested shares/units outstanding (in shares/units)									113,241,341	103,200,568	99,972,359
Effect of dilutive securities (in units)									478,281	648,600	510,006
Diluted weighted average vested shares and common stock/ unit equivalents outstanding (in shares/units)									113,719,622	103,849,168	100,482,365
Basic earnings per unit:
Net income available to common unitholders per unit - basic (in dollars per unit)	$ 0.67	$ 0.42	$ 0.17	$ 0.37	$ 0.68	$ 0.41	$ 0.41	$ 0.36	$ 1.63	$ 1.87	$ 2.56
Diluted earnings per unit:
Net income available to common unitholders per unit - diluted (in dollars per unit)	0.67	0.42	0.17	0.37	0.67	0.41	0.41	0.36	$ 1.63	$ 1.86	$ 2.55
Kilroy Realty L.P. [Member]
Numerator:
Net income attributable to common unitholders									$ 189,609	$ 198,738	$ 263,210
Allocation to participating securities									(2,229)	(2,119)	(2,004)
Numerator for basic and diluted net income available to common stockholders									$ 187,380	$ 196,619	$ 261,206
Denominator:
Basic weighted average vested shares/units outstanding (in shares/units)									115,095,506	105,223,975	102,025,276
Effect of dilutive securities (in units)									478,281	648,600	510,006
Diluted weighted average vested shares and common stock/ unit equivalents outstanding (in shares/units)									115,573,787	105,872,575	102,535,282
Basic earnings per unit:
Net income available to common unitholders per unit - basic (in dollars per unit)	0.67	0.42	0.16	0.37	0.68	0.41	0.41	0.36	$ 1.63	$ 1.87	$ 2.56
Diluted earnings per unit:
Net income available to common unitholders per unit - diluted (in dollars per unit)	$ 0.67	$ 0.42	$ 0.16	$ 0.36	$ 0.67	$ 0.41	$ 0.41	$ 0.36	$ 1.62	$ 1.86	$ 2.55

Supplemental Cash Flow Inform_4

Supplemental Cash Flow Information of the Company - Supplemental Cash Flow (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2019
SUPPLEMENTAL CASH FLOWS INFORMATION:
Cash paid for interest, net of capitalized interest of $75,852, $77,666, and $65,627 as of December 31, 2020, 2019 and 2018, respectively	$ 61,741	$ 43,607	$ 44,697
Capitalized interest	75,852	77,666	65,627
Cash paid for amounts included in the measurement of ground lease liabilities	5,744	5,224
Cash paid for amounts included in the measurement of ground lease liabilities			4,398
NON-CASH INVESTING TRANSACTIONS:
Accrual for expenditures for operating properties and development properties	189,161	162,654	158,626
Tenant improvements funded directly by tenants	11,592	10,268	13,968
Assumption of other assets and liabilities in connection with operating and development property acquisitions, net (Note 3)	0	10,267	40,624
Initial measurement of operating right of use ground lease assets (Notes 2, 3 and 18)	95,523	96,348		$ 96,272
Initial measurement of operating ground lease liabilities (Notes 2, 3 and 18)	97,778	98,400		$ 98,349
NON-CASH FINANCING TRANSACTIONS:
Accrual of dividends and distributions payable to common stockholders and common unitholders (Notes 13 and 27)	59,431	53,219	47,559
Exchange of common units of the Operating Partnership into shares of the Company’s common stock	$ 37,640	$ 78	$ 1,962

Supplemental Cash Flow Inform_5

Supplemental Cash Flow Information of the Company - Cash and Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Roll Forward]
Cash and cash equivalents	$ 731,991	$ 60,044	$ 51,604	$ 57,649
Restricted cash	91,139	16,300	119,430	9,149
Cash and cash equivalents and restricted cash	$ 823,130	$ 76,344	$ 171,034	$ 66,798

Supplemental Cash Flow Inform_6

Supplemental Cash Flow Information of the Operating Partnership - Supplemental Cash Flow (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2019
SUPPLEMENTAL CASH FLOWS INFORMATION:
Cash paid for interest, net of capitalized interest of $75,852, $77,666, and $65,627 as of December 31, 2020, 2019 and 2018, respectively	$ 61,741	$ 43,607	$ 44,697
Capitalized interest	75,852	77,666	65,627
Cash paid for amounts included in the measurement of ground lease liabilities	5,744	5,224
Cash paid for amounts included in the measurement of ground lease liabilities			4,398
NON-CASH INVESTING TRANSACTIONS:
Accrual for expenditures for operating properties and development properties	189,161	162,654	158,626
Tenant improvements funded directly by tenants	11,592	10,268	13,968
Assumption of accrued liabilities in connection with acquisitions (Note 3)	0	10,267	40,624
Initial measurement of operating right of use ground lease assets (Notes 2, 3 and 18)	95,523	96,348		$ 96,272
Initial measurement of operating ground lease liabilities (Notes 2, 3 and 18)	97,778	98,400		98,349
NON-CASH FINANCING TRANSACTIONS:
Accrual of distributions payable to common unitholders (Notes 14 and 27)	59,431	53,219	47,559
Kilroy Realty L.P. [Member]
SUPPLEMENTAL CASH FLOWS INFORMATION:
Cash paid for interest, net of capitalized interest of $75,852, $77,666, and $65,627 as of December 31, 2020, 2019 and 2018, respectively	61,741	43,607	44,697
Capitalized interest	75,852	77,666	65,627
Cash paid for amounts included in the measurement of ground lease liabilities	5,744	5,224
Cash paid for amounts included in the measurement of ground lease liabilities			4,398
NON-CASH INVESTING TRANSACTIONS:
Accrual for expenditures for operating properties and development properties	189,161	162,654	158,626
Tenant improvements funded directly by tenants	11,592	10,268	13,968
Assumption of accrued liabilities in connection with acquisitions (Note 3)	0	10,267	40,624
Initial measurement of operating right of use ground lease assets (Notes 2, 3 and 18)	95,523	96,348		96,272
Initial measurement of operating ground lease liabilities (Notes 2, 3 and 18)	97,778	98,400		$ 98,349
NON-CASH FINANCING TRANSACTIONS:
Accrual of distributions payable to common unitholders (Notes 14 and 27)	$ 59,431	$ 53,219	$ 47,559

Supplemental Cash Flow Inform_7

Supplemental Cash Flow Information of the Operating Partnership - Cash and Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Roll Forward]
Cash and cash equivalents	$ 731,991	$ 60,044	$ 51,604	$ 57,649
Restricted cash	91,139	16,300	119,430	9,149
Cash and cash equivalents and restricted cash	823,130	76,344	171,034	66,798
Kilroy Realty L.P. [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Roll Forward]
Cash and cash equivalents	731,991	60,044	51,604	57,649
Restricted cash	91,139	16,300	119,430	9,149
Cash and cash equivalents and restricted cash	$ 823,130	$ 76,344	$ 171,034	$ 66,798

Tax Treatment of Distribution_2

Tax Treatment of Distributions - Dividends (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Class of Stock [Line Items]
Dividends declared per common share (in dollars per share)	$ 1.97	$ 1.91	$ 1.79
Common Stock [Member]
Class of Stock [Line Items]
Dividends declared per common share (in dollars per share)	1.970	1.910	1.790
Less: Dividends declared in the current year and paid in the following year (in dollars per share)	(0.500)	(0.485)	(0.455)
Add: Dividends declared in the prior year and paid in the current year (in dollars per share)	0.485	0.455	0.425
Dividends paid per common share (in dollars per share)	$ 1.955	$ 1.880	$ 1.760

Tax Treatment of Distribution_3

Tax Treatment of Distributions - Dividends Tax Treatment (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Treatment of Dividends Paid [Line Items]
Capital gains, federal statutory tax rate	20.00%
Common Stock [Member]
Income Tax Treatment of Dividends Paid [Line Items]
Dividends paid per common share (in dollars per share)	$ 1.955	$ 1.880	$ 1.760
Tax Treatment, Ordinary income [Member] | Common Stock [Member]
Income Tax Treatment of Dividends Paid [Line Items]
Dividends paid per common share (in dollars per share)	$ 1.474	$ 0.939	$ 1.474
Dividends paid per common share, percentage	75.40%	49.95%	83.73%
Tax Treatment, Qualified dividend [Member] | Common Stock [Member]
Income Tax Treatment of Dividends Paid [Line Items]
Dividends paid per common share (in dollars per share)	$ 0.002	$ 0.004	$ 0.003
Dividends paid per common share, percentage	0.12%	0.21%	0.19%
Tax Treatment, Return of capital [Member] | Common Stock [Member]
Income Tax Treatment of Dividends Paid [Line Items]
Dividends paid per common share (in dollars per share)	$ 0.162	$ 0.312	$ 0.275
Dividends paid per common share, percentage	8.30%	16.62%	15.64%
Tax Treatment, Capital gains [Member] | Common Stock [Member]
Income Tax Treatment of Dividends Paid [Line Items]
Dividends paid per common share (in dollars per share)	$ 0.275	$ 0.600	$ 0.008
Dividends paid per common share, percentage	14.05%	31.93%	0.44%
Tax Treatment, Unrecaptured section 1250 gains [Member] | Common Stock [Member]
Income Tax Treatment of Dividends Paid [Line Items]
Dividends paid per common share (in dollars per share)	$ 0.042	$ 0.025	$ 0
Dividends paid per common share, percentage	2.13%	1.29%	0.00%
Tax treatment [Member] | Common Stock [Member]
Income Tax Treatment of Dividends Paid [Line Items]
Dividends paid per common share (in dollars per share)	$ 1.955	$ 1.880	$ 1.760
Dividends paid per common share, percentage	100.00%	100.00%	100.00%

Quarterly Financial Informati_5

Quarterly Financial Information of the Company (Unaudited) - Summarized Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 229,332	$ 228,314	$ 219,423	$ 221,328	$ 220,235	$ 215,525	$ 200,492	$ 201,202	$ 898,397	$ 837,454	$ 747,298
Net income	83,452	54,071	24,352	45,418	77,922	48,298	47,215	41,794	207,293	215,229	277,926
Net income attributable to Kilroy Realty Corporation	78,642	49,028	19,618	39,817	72,500	43,846	42,194	36,903
Net income available to common stockholders	$ 78,642	$ 49,028	$ 19,618	$ 39,817	$ 72,500	$ 43,846	$ 42,194	$ 36,903	$ 187,105	$ 195,443	$ 258,415
Net income available to common stockholders per share/ unit—basic (dollars per share/ unit)	$ 0.67	$ 0.42	$ 0.17	$ 0.37	$ 0.68	$ 0.41	$ 0.41	$ 0.36	$ 1.63	$ 1.87	$ 2.56
Net income available to common stockholders per share/ unit—diluted (dollars per share/ unit)	$ 0.67	$ 0.42	$ 0.17	$ 0.37	$ 0.67	$ 0.41	$ 0.41	$ 0.36	$ 1.63	$ 1.86	$ 2.55

Quarterly Financial Informati_6

Quarterly Financial Information of the Operating Partnership (Unaudited) - Summarized Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Effect of Fourth Quarter Events [Line Items]
Revenues	$ 229,332	$ 228,314	$ 219,423	$ 221,328	$ 220,235	$ 215,525	$ 200,492	$ 201,202	$ 898,397	$ 837,454	$ 747,298
Net income	83,452	54,071	24,352	45,418	77,922	48,298	47,215	41,794	207,293	215,229	277,926
Net income attributable to the Operating Partnership	78,642	49,028	19,618	39,817	72,500	43,846	42,194	36,903
Net income available to common stockholders	$ 78,642	$ 49,028	$ 19,618	$ 39,817	$ 72,500	$ 43,846	$ 42,194	$ 36,903	$ 187,105	$ 195,443	$ 258,415
Net income available to common stockholders per share/ unit—basic (dollars per share/ unit)	$ 0.67	$ 0.42	$ 0.17	$ 0.37	$ 0.68	$ 0.41	$ 0.41	$ 0.36	$ 1.63	$ 1.87	$ 2.56
Net income available to common stockholders per share/ unit—diluted (dollars per share/ unit)	$ 0.67	$ 0.42	$ 0.17	$ 0.37	$ 0.67	$ 0.41	$ 0.41	$ 0.36	$ 1.63	$ 1.86	$ 2.55
Kilroy Realty L.P. [Member]
Effect of Fourth Quarter Events [Line Items]
Revenues	$ 229,332	$ 228,314	$ 219,423	$ 221,328	$ 220,235	$ 215,525	$ 200,492	$ 201,202	$ 898,397	$ 837,454	$ 747,298
Net income	83,452	54,071	24,352	45,418	77,922	48,298	47,215	41,794	207,293	215,229	277,926
Net income attributable to the Operating Partnership	79,654	49,728	19,838	40,389	73,740	44,589	42,901	37,508
Net income available to common stockholders	$ 79,654	$ 49,728	$ 19,838	$ 40,389	$ 73,740	$ 44,589	$ 42,901	$ 37,508	$ 189,609	$ 198,738	$ 263,210
Net income available to common stockholders per share/ unit—basic (dollars per share/ unit)	$ 0.67	$ 0.42	$ 0.16	$ 0.37	$ 0.68	$ 0.41	$ 0.41	$ 0.36	$ 1.63	$ 1.87	$ 2.56
Net income available to common stockholders per share/ unit—diluted (dollars per share/ unit)	$ 0.67	$ 0.42	$ 0.16	$ 0.36	$ 0.67	$ 0.41	$ 0.41	$ 0.36	$ 1.62	$ 1.86	$ 2.55

Subsequent Events - Narrative (

Subsequent Events - Narrative (Details) - USD ($) $ in Millions	Jan. 29, 2021	Jan. 15, 2021	Dec. 31, 2020
Kilroy Realty 2006 Incentive Award Plan [Member]
Subsequent Event [Line Items]
Share-based compensation arrangement by share-based payment award, number of shares available for grant			1,500,000
Subsequent event [Member]
Subsequent Event [Line Items]
Payments of dividends		$ 59.4
Subsequent event [Member] | Kilroy Realty 2006 Incentive Award Plan [Member] | Time-Based Restricted Stock Units (RSUs) [Member] | Chief Executive Officer [Member]
Subsequent Event [Line Items]
Share-based compensation arrangement by share-based payment award, number of shares available for grant	102,799
Subsequent event [Member] | Kilroy Realty 2006 Incentive Award Plan [Member] | Market measure-based Restricted Stock Units (RSUs) [Member] | Chief Executive Officer [Member]
Subsequent Event [Line Items]
Recognition period	3 years

Schedule II - Valuation and Q_2

Schedule II - Valuation and Qualifying Accounts - Allowances (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Notes receivable, valuation allowance	$ 1,700	$ 700	$ 2,900
Uncollectible tenant receivables [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	1,171	4,639	2,309
Balance, Beginning of Period, adjusted			512
Charged to Costs and Expenses	1,977	907	2,604
Deductions (3)	(1,349)	(248)	(274)
Balance at End of Period	1,799	1,171	4,639
Allowance for deferred rent [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	1,552	3,339	3,238
Balance, Beginning of Period, adjusted			195
Charged to Costs and Expenses	832	1,357	165
Deductions (3)	(1,580)	0	(64)
Balance at End of Period	$ 804	$ 1,552	$ 3,339

Schedule III - Real Estate an_2

Schedule III - Real Estate and Accumulated Depreciation - Schedule of Real Estate and Accumulated Depreciation (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)ft²	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, encumbrances	$ 254,365
Initial cost, land and improvements	2,371,628
Initial cost, buildings and Improvements	2,699,959
Costs capitalized subsequent to acquisition/ improvement	5,118,459
Land and improvements, gross	2,503,621
Buildings and improvements, gross	7,686,425
Land and improvements and buildings and improvements, gross	10,190,046
Accumulated depreciation	$ 1,798,646	$ 1,561,361	$ 1,391,368	$ 1,264,162
Rentable square feet | ft²	14,620,166
3101-3243 S. La Cienega Blvd., Culver City, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 150,718
Initial cost, buildings and Improvements	31,033
Costs capitalized subsequent to acquisition/ improvement	227
Land and improvements, gross	150,718
Buildings and improvements, gross	31,259
Land and improvements and buildings and improvements, gross	181,977
Accumulated depreciation	$ 6,127
Depreciation life	35 years
Rentable square feet | ft²	151,908
2240 E. Imperial Highway, El Segundo, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 1,044
Initial cost, buildings and Improvements	11,763
Costs capitalized subsequent to acquisition/ improvement	29,551
Land and improvements, gross	1,048
Buildings and improvements, gross	41,310
Land and improvements and buildings and improvements, gross	42,358
Accumulated depreciation	$ 28,203
Depreciation life	35 years
Rentable square feet | ft²	122,870
2250 E. Imperial Highway, El Segundo, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 2,579
Initial cost, buildings and Improvements	29,062
Costs capitalized subsequent to acquisition/ improvement	36,311
Land and improvements, gross	2,547
Buildings and improvements, gross	65,405
Land and improvements and buildings and improvements, gross	67,952
Accumulated depreciation	$ 56,603
Depreciation life	35 years
Rentable square feet | ft²	298,728
2260 E. Imperial Highway, El Segundo, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 2,518
Initial cost, buildings and Improvements	28,370
Costs capitalized subsequent to acquisition/ improvement	36,781
Land and improvements, gross	2,547
Buildings and improvements, gross	65,122
Land and improvements and buildings and improvements, gross	67,669
Accumulated depreciation	$ 18,563
Depreciation life	35 years
Rentable square feet | ft²	298,728
909 N. Pacific Coast Highway, El Segundo, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 3,577
Initial cost, buildings and Improvements	34,042
Costs capitalized subsequent to acquisition/ improvement	51,773
Land and improvements, gross	3,577
Buildings and improvements, gross	85,815
Land and improvements and buildings and improvements, gross	89,392
Accumulated depreciation	$ 44,727
Depreciation life	35 years
Rentable square feet | ft²	244,136
999 N. Pacific Coast Highway, El Segundo, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 1,407
Initial cost, buildings and Improvements	34,326
Costs capitalized subsequent to acquisition/ improvement	17,295
Land and improvements, gross	1,407
Buildings and improvements, gross	51,621
Land and improvements and buildings and improvements, gross	53,028
Accumulated depreciation	$ 27,429
Depreciation life	35 years
Rentable square feet | ft²	128,588
1350 Ivar Ave., Los Angeles, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 1,575
Initial cost, buildings and Improvements	0
Costs capitalized subsequent to acquisition/ improvement	13,725
Land and improvements, gross	1,575
Buildings and improvements, gross	13,725
Land and improvements and buildings and improvements, gross	15,300
Accumulated depreciation	$ 65
Depreciation life	35 years
Rentable square feet | ft²	16,448
1355 Vine St., Los Angeles, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 17,588
Initial cost, buildings and Improvements	0
Costs capitalized subsequent to acquisition/ improvement	114,603
Land and improvements, gross	17,588
Buildings and improvements, gross	114,603
Land and improvements and buildings and improvements, gross	132,191
Accumulated depreciation	$ 549
Depreciation life	35 years
Rentable square feet | ft²	183,129
1375 Vine St., Los Angeles, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 15,578
Initial cost, buildings and Improvements	0
Costs capitalized subsequent to acquisition/ improvement	97,470
Land and improvements, gross	15,578
Buildings and improvements, gross	97,470
Land and improvements and buildings and improvements, gross	113,048
Accumulated depreciation	$ 461
Depreciation life	35 years
Rentable square feet | ft²	159,236
1395 Vine St., Los Angeles, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 278
Initial cost, buildings and Improvements	0
Costs capitalized subsequent to acquisition/ improvement	3,138
Land and improvements, gross	278
Buildings and improvements, gross	3,138
Land and improvements and buildings and improvements, gross	3,417
Accumulated depreciation	$ 16
Depreciation life	35 years
Rentable square feet | ft²	2,575
6115 W. Sunset Blvd., Los Angeles, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 1,313
Initial cost, buildings and Improvements	3
Costs capitalized subsequent to acquisition/ improvement	16,454
Land and improvements, gross	2,455
Buildings and improvements, gross	15,315
Land and improvements and buildings and improvements, gross	17,770
Accumulated depreciation	$ 2,787
Depreciation life	35 years
Rentable square feet | ft²	26,105
6121 W. Sunset Blvd., Los Angeles, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 11,120
Initial cost, buildings and Improvements	4,256
Costs capitalized subsequent to acquisition/ improvement	43,983
Land and improvements, gross	8,703
Buildings and improvements, gross	50,656
Land and improvements and buildings and improvements, gross	59,359
Accumulated depreciation	$ 8,894
Depreciation life	35 years
Rentable square feet | ft²	91,173
1525 N. Gower Street, Los Angeles, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 1,318
Initial cost, buildings and Improvements	3
Costs capitalized subsequent to acquisition/ improvement	9,641
Land and improvements, gross	1,318
Buildings and improvements, gross	9,645
Land and improvements and buildings and improvements, gross	10,962
Accumulated depreciation	$ 1,542
Depreciation life	35 years
Rentable square feet | ft²	9,610
1575 N. Gower Street, Los Angeles, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 22,153
Initial cost, buildings and Improvements	51
Costs capitalized subsequent to acquisition/ improvement	119,496
Land and improvements, gross	22,153
Buildings and improvements, gross	119,547
Land and improvements and buildings and improvements, gross	141,700
Accumulated depreciation	$ 15,482
Depreciation life	35 years
Rentable square feet | ft²	251,245
1500 N. El Centro Avenue, Los Angeles, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 9,235
Initial cost, buildings and Improvements	21
Costs capitalized subsequent to acquisition/ improvement	58,988
Land and improvements, gross	9,235
Buildings and improvements, gross	59,009
Land and improvements and buildings and improvements, gross	68,244
Accumulated depreciation	$ 12,666
Depreciation life	35 years
Rentable square feet | ft²	104,504
1550 N. El Centro Avenue, Los Angeles, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 16,970
Initial cost, buildings and Improvements	39
Costs capitalized subsequent to acquisition/ improvement	136,137
Land and improvements, gross	16,970
Buildings and improvements, gross	136,176
Land and improvements and buildings and improvements, gross	153,146
Accumulated depreciation	$ 17,894
Depreciation life	35 years
Rentable square feet | ft²	0
6255 W. Sunset Blvd., Los Angeles, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 18,111
Initial cost, buildings and Improvements	60,320
Costs capitalized subsequent to acquisition/ improvement	49,265
Land and improvements, gross	18,111
Buildings and improvements, gross	109,585
Land and improvements and buildings and improvements, gross	127,696
Accumulated depreciation	$ 41,735
Depreciation life	35 years
Rentable square feet | ft²	323,920
3750 Kilroy Airport Way, Long Beach, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 0
Initial cost, buildings and Improvements	1,941
Costs capitalized subsequent to acquisition/ improvement	13,113
Land and improvements, gross	0
Buildings and improvements, gross	15,054
Land and improvements and buildings and improvements, gross	15,054
Accumulated depreciation	$ 11,247
Depreciation life	35 years
Rentable square feet | ft²	10,718
3760 Kilroy Airport Way, Long Beach, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 0
Initial cost, buildings and Improvements	17,467
Costs capitalized subsequent to acquisition/ improvement	16,687
Land and improvements, gross	0
Buildings and improvements, gross	34,154
Land and improvements and buildings and improvements, gross	34,154
Accumulated depreciation	$ 28,166
Depreciation life	35 years
Rentable square feet | ft²	166,761
3780 Kilroy Airport Way, Long Beach, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 0
Initial cost, buildings and Improvements	22,319
Costs capitalized subsequent to acquisition/ improvement	31,855
Land and improvements, gross	0
Buildings and improvements, gross	54,174
Land and improvements and buildings and improvements, gross	54,174
Accumulated depreciation	$ 41,573
Depreciation life	35 years
Rentable square feet | ft²	221,452
3800 Kilroy Airport Way, Long Beach, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 0
Initial cost, buildings and Improvements	19,408
Costs capitalized subsequent to acquisition/ improvement	22,252
Land and improvements, gross	0
Buildings and improvements, gross	41,660
Land and improvements and buildings and improvements, gross	41,660
Accumulated depreciation	$ 26,473
Depreciation life	35 years
Rentable square feet | ft²	192,476
3840 Kilroy Airport Way, Long Beach, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 0
Initial cost, buildings and Improvements	13,586
Costs capitalized subsequent to acquisition/ improvement	11,755
Land and improvements, gross	0
Buildings and improvements, gross	25,341
Land and improvements and buildings and improvements, gross	25,341
Accumulated depreciation	$ 16,793
Depreciation life	35 years
Rentable square feet | ft²	136,026
3880 Kilroy Airport Way, Long Beach, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 0
Initial cost, buildings and Improvements	9,704
Costs capitalized subsequent to acquisition/ improvement	11,827
Land and improvements, gross	0
Buildings and improvements, gross	21,531
Land and improvements and buildings and improvements, gross	21,531
Accumulated depreciation	$ 5,220
Depreciation life	35 years
Rentable square feet | ft²	96,923
3900 Kilroy Airport Way, Long Beach, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 0
Initial cost, buildings and Improvements	12,615
Costs capitalized subsequent to acquisition/ improvement	13,208
Land and improvements, gross	0
Buildings and improvements, gross	25,823
Land and improvements and buildings and improvements, gross	25,823
Accumulated depreciation	$ 19,261
Depreciation life	35 years
Rentable square feet | ft²	130,935
Kilroy Airport Center, Phase IV, Long Beach, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 0
Initial cost, buildings and Improvements	0
Costs capitalized subsequent to acquisition/ improvement	4,997
Land and improvements, gross	0
Buildings and improvements, gross	4,997
Land and improvements and buildings and improvements, gross	4,997
Accumulated depreciation	$ 4,997
Depreciation life	35 years
Rentable square feet | ft²	0
8560 W. Sunset Blvd, West Hollywood, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 9,720
Initial cost, buildings and Improvements	50,956
Costs capitalized subsequent to acquisition/ improvement	1,930
Land and improvements, gross	9,720
Buildings and improvements, gross	52,886
Land and improvements and buildings and improvements, gross	62,606
Accumulated depreciation	$ 8,351
Depreciation life	35 years
Rentable square feet | ft²	74,842
8570 W. Sunset Blvd, West Hollywood, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 31,693
Initial cost, buildings and Improvements	27,974
Costs capitalized subsequent to acquisition/ improvement	6,497
Land and improvements, gross	31,693
Buildings and improvements, gross	34,471
Land and improvements and buildings and improvements, gross	66,163
Accumulated depreciation	$ 4,121
Depreciation life	35 years
Rentable square feet | ft²	45,941
8580 W. Sunset Blvd, West Hollywood, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 10,013
Initial cost, buildings and Improvements	3,695
Costs capitalized subsequent to acquisition/ improvement	1,219
Land and improvements, gross	10,013
Buildings and improvements, gross	4,914
Land and improvements and buildings and improvements, gross	14,927
Accumulated depreciation	$ 523
Depreciation life	35 years
Rentable square feet | ft²	7,126
8590 W. Sunset Blvd, West Hollywood, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 39,954
Initial cost, buildings and Improvements	27,884
Costs capitalized subsequent to acquisition/ improvement	5,487
Land and improvements, gross	39,954
Buildings and improvements, gross	33,371
Land and improvements and buildings and improvements, gross	73,325
Accumulated depreciation	$ 4,473
Depreciation life	35 years
Rentable square feet | ft²	55,302
12100 W. Olympic Blvd., Los Angeles, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 352
Initial cost, buildings and Improvements	45,611
Costs capitalized subsequent to acquisition/ improvement	20,191
Land and improvements, gross	9,633
Buildings and improvements, gross	56,520
Land and improvements and buildings and improvements, gross	66,154
Accumulated depreciation	$ 30,836
Depreciation life	35 years
Rentable square feet | ft²	152,048
12200 W. Olympic Blvd., Los Angeles, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 4,329
Initial cost, buildings and Improvements	35,488
Costs capitalized subsequent to acquisition/ improvement	25,506
Land and improvements, gross	3,977
Buildings and improvements, gross	61,346
Land and improvements and buildings and improvements, gross	65,323
Accumulated depreciation	$ 42,135
Depreciation life	35 years
Rentable square feet | ft²	150,832
12233 Olympic Blvd., Los Angeles, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 22,100
Initial cost, buildings and Improvements	53,170
Costs capitalized subsequent to acquisition/ improvement	5,258
Land and improvements, gross	22,100
Buildings and improvements, gross	58,428
Land and improvements and buildings and improvements, gross	80,528
Accumulated depreciation	$ 16,326
Depreciation life	35 years
Rentable square feet | ft²	151,029
12312 W. Olympic Blvd., Los Angeles, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 3,325
Initial cost, buildings and Improvements	12,202
Costs capitalized subsequent to acquisition/ improvement	12,345
Land and improvements, gross	3,399
Buildings and improvements, gross	24,473
Land and improvements and buildings and improvements, gross	27,872
Accumulated depreciation	$ 14,923
Depreciation life	35 years
Rentable square feet | ft²	76,644
1633 26th St., Santa Monica, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 2,080
Initial cost, buildings and Improvements	6,672
Costs capitalized subsequent to acquisition/ improvement	4,006
Land and improvements, gross	2,040
Buildings and improvements, gross	10,718
Land and improvements and buildings and improvements, gross	12,758
Accumulated depreciation	$ 7,497
Depreciation life	35 years
Rentable square feet | ft²	43,857
2100/2110 Colorado Ave., Santa Monica, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 5,474
Initial cost, buildings and Improvements	26,087
Costs capitalized subsequent to acquisition/ improvement	14,915
Land and improvements, gross	5,476
Buildings and improvements, gross	41,000
Land and improvements and buildings and improvements, gross	46,476
Accumulated depreciation	$ 27,393
Depreciation life	35 years
Rentable square feet | ft²	102,864
3130 Wilshire Blvd., Santa Monica, [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 8,921
Initial cost, buildings and Improvements	6,579
Costs capitalized subsequent to acquisition/ improvement	17,147
Land and improvements, gross	9,188
Buildings and improvements, gross	23,459
Land and improvements and buildings and improvements, gross	32,647
Accumulated depreciation	$ 17,318
Depreciation life	35 years
Rentable square feet | ft²	90,074
501 Santa Monica Blvd., Santa Monica, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 4,547
Initial cost, buildings and Improvements	12,044
Costs capitalized subsequent to acquisition/ improvement	16,304
Land and improvements, gross	4,551
Buildings and improvements, gross	28,344
Land and improvements and buildings and improvements, gross	32,895
Accumulated depreciation	$ 19,067
Depreciation life	35 years
Rentable square feet | ft²	76,803
12225 El Camino Real, Del Mar, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 1,700
Initial cost, buildings and Improvements	9,633
Costs capitalized subsequent to acquisition/ improvement	3,864
Land and improvements, gross	1,673
Buildings and improvements, gross	13,524
Land and improvements and buildings and improvements, gross	15,197
Accumulated depreciation	$ 9,622
Depreciation life	35 years
Rentable square feet | ft²	58,401
12235 El Camino Real, Del Mar, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 1,507
Initial cost, buildings and Improvements	8,543
Costs capitalized subsequent to acquisition/ improvement	9,255
Land and improvements, gross	1,540
Buildings and improvements, gross	17,765
Land and improvements and buildings and improvements, gross	19,305
Accumulated depreciation	$ 11,193
Depreciation life	35 years
Rentable square feet | ft²	53,751
12340 El Camino Real, Del Mar, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 4,201
Initial cost, buildings and Improvements	13,896
Costs capitalized subsequent to acquisition/ improvement	12,195
Land and improvements, gross	4,201
Buildings and improvements, gross	26,091
Land and improvements and buildings and improvements, gross	30,292
Accumulated depreciation	$ 13,226
Depreciation life	35 years
Rentable square feet | ft²	89,272
12390 El Camino Real, Del Mar, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 3,453
Initial cost, buildings and Improvements	11,981
Costs capitalized subsequent to acquisition/ improvement	9,541
Land and improvements, gross	3,453
Buildings and improvements, gross	21,522
Land and improvements and buildings and improvements, gross	24,975
Accumulated depreciation	$ 10,742
Depreciation life	35 years
Rentable square feet | ft²	70,140
12348 High Bluff Dr., Del Mar, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 1,629
Initial cost, buildings and Improvements	3,096
Costs capitalized subsequent to acquisition/ improvement	6,890
Land and improvements, gross	1,629
Buildings and improvements, gross	9,986
Land and improvements and buildings and improvements, gross	11,615
Accumulated depreciation	$ 6,963
Depreciation life	35 years
Rentable square feet | ft²	39,193
12400 High Bluff Dr., Del Mar, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 15,167
Initial cost, buildings and Improvements	40,497
Costs capitalized subsequent to acquisition/ improvement	16,850
Land and improvements, gross	15,167
Buildings and improvements, gross	57,347
Land and improvements and buildings and improvements, gross	72,514
Accumulated depreciation	$ 30,685
Depreciation life	35 years
Rentable square feet | ft²	210,732
12770 El Camino Real, Del Mar, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 9,360
Initial cost, buildings and Improvements	0
Costs capitalized subsequent to acquisition/ improvement	34,212
Land and improvements, gross	9,360
Buildings and improvements, gross	34,212
Land and improvements and buildings and improvements, gross	43,572
Accumulated depreciation	$ 4,493
Depreciation life	35 years
Rentable square feet | ft²	73,032
12780 El Camino Real, Del Mar, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 18,398
Initial cost, buildings and Improvements	54,954
Costs capitalized subsequent to acquisition/ improvement	22,922
Land and improvements, gross	18,398
Buildings and improvements, gross	77,876
Land and improvements and buildings and improvements, gross	96,274
Accumulated depreciation	$ 18,909
Depreciation life	35 years
Rentable square feet | ft²	140,591
12790 El Camino Real, Del Mar, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 10,252
Initial cost, buildings and Improvements	21,236
Costs capitalized subsequent to acquisition/ improvement	8,485
Land and improvements, gross	10,252
Buildings and improvements, gross	29,721
Land and improvements and buildings and improvements, gross	39,973
Accumulated depreciation	$ 6,812
Depreciation life	35 years
Rentable square feet | ft²	78,836
12860 El Camino Real, Del Mar, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 0
Initial cost, buildings and Improvements	0
Costs capitalized subsequent to acquisition/ improvement	60,675
Land and improvements, gross	11,326
Buildings and improvements, gross	49,349
Land and improvements and buildings and improvements, gross	60,675
Accumulated depreciation	$ 602
Depreciation life	35 years
Rentable square feet | ft²	0
12830 El Camino Real, Del Mar, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 0
Initial cost, buildings and Improvements	0
Costs capitalized subsequent to acquisition/ improvement	134,776
Land and improvements, gross	28,645
Buildings and improvements, gross	106,131
Land and improvements and buildings and improvements, gross	134,776
Accumulated depreciation	$ 885
Depreciation life	35 years
Rentable square feet | ft²	0
3579 Valley Centre Dr., Del Mar, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 2,167
Initial cost, buildings and Improvements	6,897
Costs capitalized subsequent to acquisition/ improvement	9,559
Land and improvements, gross	2,858
Buildings and improvements, gross	15,765
Land and improvements and buildings and improvements, gross	18,623
Accumulated depreciation	$ 10,397
Depreciation life	35 years
Rentable square feet | ft²	54,960
3611 Valley Centre Dr., Del Mar, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 4,184
Initial cost, buildings and Improvements	19,352
Costs capitalized subsequent to acquisition/ improvement	25,934
Land and improvements, gross	5,259
Buildings and improvements, gross	44,212
Land and improvements and buildings and improvements, gross	49,470
Accumulated depreciation	$ 27,028
Depreciation life	35 years
Rentable square feet | ft²	130,109
3661 Valley Centre Dr., Del Mar, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 4,038
Initial cost, buildings and Improvements	21,144
Costs capitalized subsequent to acquisition/ improvement	18,897
Land and improvements, gross	4,725
Buildings and improvements, gross	39,354
Land and improvements and buildings and improvements, gross	44,079
Accumulated depreciation	$ 24,083
Depreciation life	35 years
Rentable square feet | ft²	128,364
3721 Valley Centre Dr., Del Mar, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 4,297
Initial cost, buildings and Improvements	18,967
Costs capitalized subsequent to acquisition/ improvement	14,973
Land and improvements, gross	4,254
Buildings and improvements, gross	33,983
Land and improvements and buildings and improvements, gross	38,237
Accumulated depreciation	$ 19,134
Depreciation life	35 years
Rentable square feet | ft²	115,193
3811 Valley Centre Dr., Del Mar, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 3,452
Initial cost, buildings and Improvements	16,152
Costs capitalized subsequent to acquisition/ improvement	20,540
Land and improvements, gross	4,457
Buildings and improvements, gross	35,687
Land and improvements and buildings and improvements, gross	40,144
Accumulated depreciation	$ 24,154
Depreciation life	35 years
Rentable square feet | ft²	112,067
3745 Paseo Place, Del Mar, CA (Retail) [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 24,358
Initial cost, buildings and Improvements	0
Costs capitalized subsequent to acquisition/ improvement	72,290
Land and improvements, gross	24,358
Buildings and improvements, gross	72,290
Land and improvements and buildings and improvements, gross	96,648
Accumulated depreciation	$ 4,435
Depreciation life	35 years
Rentable square feet | ft²	95,871
13280 Evening Creek Dr. South, I-15 Corridor, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 3,701
Initial cost, buildings and Improvements	8,398
Costs capitalized subsequent to acquisition/ improvement	4,818
Land and improvements, gross	3,701
Buildings and improvements, gross	13,216
Land and improvements and buildings and improvements, gross	16,917
Accumulated depreciation	$ 6,354
Depreciation life	35 years
Rentable square feet | ft²	41,196
13290 Evening Creek Dr. South, I-15 Corridor, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 5,229
Initial cost, buildings and Improvements	11,871
Costs capitalized subsequent to acquisition/ improvement	6,150
Land and improvements, gross	5,229
Buildings and improvements, gross	18,021
Land and improvements and buildings and improvements, gross	23,250
Accumulated depreciation	$ 7,665
Depreciation life	35 years
Rentable square feet | ft²	61,180
13480 Evening Creek Dr. South, I-15 Corridor, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 7,997
Initial cost, buildings and Improvements	0
Costs capitalized subsequent to acquisition/ improvement	52,581
Land and improvements, gross	7,997
Buildings and improvements, gross	52,581
Land and improvements and buildings and improvements, gross	60,578
Accumulated depreciation	$ 21,940
Depreciation life	35 years
Rentable square feet | ft²	154,157
13500 Evening Creek Dr. South, I-15 Corridor, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 7,581
Initial cost, buildings and Improvements	35,903
Costs capitalized subsequent to acquisition/ improvement	23,609
Land and improvements, gross	7,580
Buildings and improvements, gross	59,513
Land and improvements and buildings and improvements, gross	67,093
Accumulated depreciation	$ 24,861
Depreciation life	35 years
Rentable square feet | ft²	137,658
13520 Evening Creek Dr. South, I-15 Corridor, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 7,581
Initial cost, buildings and Improvements	35,903
Costs capitalized subsequent to acquisition/ improvement	19,454
Land and improvements, gross	7,580
Buildings and improvements, gross	55,358
Land and improvements and buildings and improvements, gross	62,938
Accumulated depreciation	$ 27,289
Depreciation life	35 years
Rentable square feet | ft²	146,701
2305 Historic Decatur Rd., Point Loma, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 5,240
Initial cost, buildings and Improvements	22,220
Costs capitalized subsequent to acquisition/ improvement	7,650
Land and improvements, gross	5,240
Buildings and improvements, gross	29,870
Land and improvements and buildings and improvements, gross	35,110
Accumulated depreciation	$ 12,291
Depreciation life	35 years
Rentable square feet | ft²	107,456
4690 Executive Dr., University Towne Centre, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 1,623
Initial cost, buildings and Improvements	7,926
Costs capitalized subsequent to acquisition/ improvement	3,725
Land and improvements, gross	1,623
Buildings and improvements, gross	11,651
Land and improvements and buildings and improvements, gross	13,274
Accumulated depreciation	$ 8,314
Depreciation life	35 years
Rentable square feet | ft²	47,846
Bohannon Drive 4100, Menlo Park, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 4,835
Initial cost, buildings and Improvements	15,526
Costs capitalized subsequent to acquisition/ improvement	932
Land and improvements, gross	4,860
Buildings and improvements, gross	16,433
Land and improvements and buildings and improvements, gross	21,293
Accumulated depreciation	$ 5,123
Depreciation life	35 years
Rentable square feet | ft²	47,379
Bohannon Drive 4200, Menlo Park, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 4,798
Initial cost, buildings and Improvements	15,406
Costs capitalized subsequent to acquisition/ improvement	3,967
Land and improvements, gross	4,662
Buildings and improvements, gross	19,509
Land and improvements and buildings and improvements, gross	24,171
Accumulated depreciation	$ 6,585
Depreciation life	35 years
Rentable square feet | ft²	45,451
Bohannon Drive 4300, Menlo Park, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 6,527
Initial cost, buildings and Improvements	20,958
Costs capitalized subsequent to acquisition/ improvement	5,373
Land and improvements, gross	6,470
Buildings and improvements, gross	26,387
Land and improvements and buildings and improvements, gross	32,858
Accumulated depreciation	$ 8,557
Depreciation life	35 years
Rentable square feet | ft²	63,079
Bohannon Drive 4400, Menlo Park, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 4,798
Initial cost, buildings and Improvements	15,406
Costs capitalized subsequent to acquisition/ improvement	3,331
Land and improvements, gross	4,939
Buildings and improvements, gross	18,597
Land and improvements and buildings and improvements, gross	23,535
Accumulated depreciation	$ 6,394
Depreciation life	35 years
Rentable square feet | ft²	48,146
Bohannon Drive 4500, Menlo Park, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 6,527
Initial cost, buildings and Improvements	20,957
Costs capitalized subsequent to acquisition/ improvement	3,811
Land and improvements, gross	6,470
Buildings and improvements, gross	24,825
Land and improvements and buildings and improvements, gross	31,295
Accumulated depreciation	$ 7,506
Depreciation life	35 years
Rentable square feet | ft²	63,078
Bohannon Drive 4600, Menlo Park, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 4,798
Initial cost, buildings and Improvements	15,406
Costs capitalized subsequent to acquisition/ improvement	4,025
Land and improvements, gross	4,939
Buildings and improvements, gross	19,290
Land and improvements and buildings and improvements, gross	24,229
Accumulated depreciation	$ 6,427
Depreciation life	35 years
Rentable square feet | ft²	48,147
Bohannon Drive 4700, Menlo Park, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 6,527
Initial cost, buildings and Improvements	20,958
Costs capitalized subsequent to acquisition/ improvement	1,584
Land and improvements, gross	6,470
Buildings and improvements, gross	22,599
Land and improvements and buildings and improvements, gross	29,069
Accumulated depreciation	$ 7,112
Depreciation life	35 years
Rentable square feet | ft²	63,078
1290-1300 Terra Bella Avenue, Mountain View, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 28,730
Initial cost, buildings and Improvements	27,555
Costs capitalized subsequent to acquisition/ improvement	61
Land and improvements, gross	28,730
Buildings and improvements, gross	27,616
Land and improvements and buildings and improvements, gross	56,346
Accumulated depreciation	$ 5,702
Depreciation life	35 years
Rentable square feet | ft²	114,175
680 E Middlefield Road, Mountain View, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 34,605
Initial cost, buildings and Improvements	0
Costs capitalized subsequent to acquisition/ improvement	56,522
Land and improvements, gross	34,605
Buildings and improvements, gross	56,522
Land and improvements and buildings and improvements, gross	91,127
Accumulated depreciation	$ 11,718
Depreciation life	35 years
Rentable square feet | ft²	170,090
690 E Middlefield Road, Mountain View, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 34,755
Initial cost, buildings and Improvements	0
Costs capitalized subsequent to acquisition/ improvement	56,764
Land and improvements, gross	34,755
Buildings and improvements, gross	56,765
Land and improvements and buildings and improvements, gross	91,519
Accumulated depreciation	$ 11,768
Depreciation life	35 years
Rentable square feet | ft²	170,823
1701 Page Mill Rd, Palo Alto, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 0
Initial cost, buildings and Improvements	99,522
Costs capitalized subsequent to acquisition/ improvement	29
Land and improvements, gross	0
Buildings and improvements, gross	99,551
Land and improvements and buildings and improvements, gross	99,551
Accumulated depreciation	$ 12,005
Depreciation life	35 years
Rentable square feet | ft²	128,688
3150 Porter Drive, Palo Alto, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 0
Initial cost, buildings and Improvements	21,715
Costs capitalized subsequent to acquisition/ improvement	410
Land and improvements, gross	0
Buildings and improvements, gross	22,125
Land and improvements and buildings and improvements, gross	22,125
Accumulated depreciation	$ 3,170
Depreciation life	35 years
Rentable square feet | ft²	36,886
900 Jefferson Ave., Redwood City, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 16,668
Initial cost, buildings and Improvements	0
Costs capitalized subsequent to acquisition/ improvement	109,377
Land and improvements, gross	18,063
Buildings and improvements, gross	107,982
Land and improvements and buildings and improvements, gross	126,045
Accumulated depreciation	$ 19,674
Depreciation life	35 years
Rentable square feet | ft²	228,505
900 Middlefield Road, Redwood City, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 7,959
Initial cost, buildings and Improvements	0
Costs capitalized subsequent to acquisition/ improvement	50,115
Land and improvements, gross	8,626
Buildings and improvements, gross	49,449
Land and improvements and buildings and improvements, gross	58,074
Accumulated depreciation	$ 8,684
Depreciation life	35 years
Rentable square feet | ft²	118,764
100 Hooper Street, San Francisco, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 78,564
Initial cost, buildings and Improvements	0
Costs capitalized subsequent to acquisition/ improvement	191,895
Land and improvements, gross	85,510
Buildings and improvements, gross	184,949
Land and improvements and buildings and improvements, gross	270,459
Accumulated depreciation	$ 11,632
Depreciation life	35 years
Rentable square feet | ft²	394,340
100 First St., San Francisco, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 49,150
Initial cost, buildings and Improvements	131,238
Costs capitalized subsequent to acquisition/ improvement	73,238
Land and improvements, gross	49,150
Buildings and improvements, gross	204,476
Land and improvements and buildings and improvements, gross	253,626
Accumulated depreciation	$ 73,294
Depreciation life	35 years
Rentable square feet | ft²	480,457
201 Third St., San Francisco, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 19,260
Initial cost, buildings and Improvements	84,018
Costs capitalized subsequent to acquisition/ improvement	69,158
Land and improvements, gross	19,260
Buildings and improvements, gross	153,176
Land and improvements and buildings and improvements, gross	172,436
Accumulated depreciation	$ 65,165
Depreciation life	35 years
Rentable square feet | ft²	346,538
250 Brannan St., San Francisco, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 7,630
Initial cost, buildings and Improvements	22,770
Costs capitalized subsequent to acquisition/ improvement	10,043
Land and improvements, gross	7,630
Buildings and improvements, gross	32,813
Land and improvements and buildings and improvements, gross	40,443
Accumulated depreciation	$ 11,783
Depreciation life	35 years
Rentable square feet | ft²	100,850
301 Brannan St., San Francisco, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 5,910
Initial cost, buildings and Improvements	22,450
Costs capitalized subsequent to acquisition/ improvement	7,704
Land and improvements, gross	5,910
Buildings and improvements, gross	30,154
Land and improvements and buildings and improvements, gross	36,064
Accumulated depreciation	$ 11,022
Depreciation life	35 years
Rentable square feet | ft²	82,834
303 Second St., San Francisco, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 63,550
Initial cost, buildings and Improvements	154,153
Costs capitalized subsequent to acquisition/ improvement	99,670
Land and improvements, gross	63,550
Buildings and improvements, gross	253,823
Land and improvements and buildings and improvements, gross	317,373
Accumulated depreciation	$ 96,466
Depreciation life	35 years
Rentable square feet | ft²	784,658
333 Brannan St., San Francisco, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 18,645
Initial cost, buildings and Improvements	0
Costs capitalized subsequent to acquisition/ improvement	80,788
Land and improvements, gross	18,645
Buildings and improvements, gross	80,787
Land and improvements and buildings and improvements, gross	99,433
Accumulated depreciation	$ 11,221
Depreciation life	35 years
Rentable square feet | ft²	185,602
345 Brannan Street, San Francisco, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 29,405
Initial cost, buildings and Improvements	113,179
Costs capitalized subsequent to acquisition/ improvement	752
Land and improvements, gross	29,403
Buildings and improvements, gross	113,933
Land and improvements and buildings and improvements, gross	143,336
Accumulated depreciation	$ 6,967
Depreciation life	35 years
Rentable square feet | ft²	110,050
350 Mission St., San Francisco, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 52,815
Initial cost, buildings and Improvements	0
Costs capitalized subsequent to acquisition/ improvement	213,312
Land and improvements, gross	52,815
Buildings and improvements, gross	213,312
Land and improvements and buildings and improvements, gross	266,127
Accumulated depreciation	$ 31,186
Depreciation life	35 years
Rentable square feet | ft²	455,340
360 Third St., San Francisco, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 0
Initial cost, buildings and Improvements	88,235
Costs capitalized subsequent to acquisition/ improvement	121,629
Land and improvements, gross	28,504
Buildings and improvements, gross	181,360
Land and improvements and buildings and improvements, gross	209,864
Accumulated depreciation	$ 53,833
Depreciation life	35 years
Rentable square feet | ft²	429,796
1800 Owens St., San Francisco, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 95,388
Initial cost, buildings and Improvements	0
Costs capitalized subsequent to acquisition/ improvement	437,715
Land and improvements, gross	95,388
Buildings and improvements, gross	437,715
Land and improvements and buildings and improvements, gross	533,103
Accumulated depreciation	$ 20,951
Depreciation life	35 years
Rentable square feet | ft²	750,370
345 Oyster Point Blvd., South San Francisco, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 13,745
Initial cost, buildings and Improvements	18,575
Costs capitalized subsequent to acquisition/ improvement	0
Land and improvements, gross	13,745
Buildings and improvements, gross	18,576
Land and improvements and buildings and improvements, gross	32,320
Accumulated depreciation	$ 1,723
Depreciation life	35 years
Rentable square feet | ft²	40,410
347 Oyster Point Blvd., South San Francisco, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 14,071
Initial cost, buildings and Improvements	18,289
Costs capitalized subsequent to acquisition/ improvement	44
Land and improvements, gross	14,071
Buildings and improvements, gross	18,333
Land and improvements and buildings and improvements, gross	32,404
Accumulated depreciation	$ 1,701
Depreciation life	35 years
Rentable square feet | ft²	39,780
349 Oyster Point Blvd., South San Francisco, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 23,112
Initial cost, buildings and Improvements	22,601
Costs capitalized subsequent to acquisition/ improvement	324
Land and improvements, gross	23,112
Buildings and improvements, gross	22,925
Land and improvements and buildings and improvements, gross	46,037
Accumulated depreciation	$ 2,968
Depreciation life	35 years
Rentable square feet | ft²	65,340
Kilroy Oyster Point, Phase I, South San Francisco, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 0
Initial cost, buildings and Improvements	0
Costs capitalized subsequent to acquisition/ improvement	620
Land and improvements, gross	0
Buildings and improvements, gross	620
Land and improvements and buildings and improvements, gross	620
Accumulated depreciation	$ 0
Depreciation life	35 years
Rentable square feet | ft²	0
505 Mathilda Ave., Sunnyvale, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 37,843
Initial cost, buildings and Improvements	1,163
Costs capitalized subsequent to acquisition/ improvement	50,450
Land and improvements, gross	37,943
Buildings and improvements, gross	51,513
Land and improvements and buildings and improvements, gross	89,456
Accumulated depreciation	$ 9,267
Depreciation life	35 years
Rentable square feet | ft²	212,322
555 Mathilda Ave., Sunnyvale, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 37,843
Initial cost, buildings and Improvements	1,163
Costs capitalized subsequent to acquisition/ improvement	50,447
Land and improvements, gross	37,943
Buildings and improvements, gross	51,510
Land and improvements and buildings and improvements, gross	89,453
Accumulated depreciation	$ 9,267
Depreciation life	35 years
Rentable square feet | ft²	212,322
599 Mathilda Ave., Sunnyvale, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 13,538
Initial cost, buildings and Improvements	12,559
Costs capitalized subsequent to acquisition/ improvement	63
Land and improvements, gross	13,538
Buildings and improvements, gross	12,622
Land and improvements and buildings and improvements, gross	26,160
Accumulated depreciation	$ 4,559
Depreciation life	35 years
Rentable square feet | ft²	76,031
605 Mathilda Ave., Sunnyvale, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 29,014
Initial cost, buildings and Improvements	891
Costs capitalized subsequent to acquisition/ improvement	77,282
Land and improvements, gross	29,090
Buildings and improvements, gross	78,096
Land and improvements and buildings and improvements, gross	107,187
Accumulated depreciation	$ 20,542
Depreciation life	35 years
Rentable square feet | ft²	162,785
601 108th Ave., Bellevue, WA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 0
Initial cost, buildings and Improvements	214,095
Costs capitalized subsequent to acquisition/ improvement	40,300
Land and improvements, gross	0
Buildings and improvements, gross	254,395
Land and improvements and buildings and improvements, gross	254,395
Accumulated depreciation	$ 88,958
Depreciation life	35 years
Rentable square feet | ft²	488,470
10900 NE 4th St., Bellevue, WA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 25,080
Initial cost, buildings and Improvements	150,877
Costs capitalized subsequent to acquisition/ improvement	45,984
Land and improvements, gross	25,080
Buildings and improvements, gross	196,861
Land and improvements and buildings and improvements, gross	221,941
Accumulated depreciation	$ 62,594
Depreciation life	35 years
Rentable square feet | ft²	428,557
837 N. 34th St., Lake Union, WA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 0
Initial cost, buildings and Improvements	37,404
Costs capitalized subsequent to acquisition/ improvement	6,293
Land and improvements, gross	0
Buildings and improvements, gross	43,697
Land and improvements and buildings and improvements, gross	43,697
Accumulated depreciation	$ 12,787
Depreciation life	35 years
Rentable square feet | ft²	112,487
701 N. 34th St., Lake Union, WA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 0
Initial cost, buildings and Improvements	48,027
Costs capitalized subsequent to acquisition/ improvement	8,545
Land and improvements, gross	0
Buildings and improvements, gross	56,572
Land and improvements and buildings and improvements, gross	56,572
Accumulated depreciation	$ 18,277
Depreciation life	35 years
Rentable square feet | ft²	141,860
801 N. 34th St., Lake Union, WA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 0
Initial cost, buildings and Improvements	58,537
Costs capitalized subsequent to acquisition/ improvement	20,661
Land and improvements, gross	0
Buildings and improvements, gross	79,198
Land and improvements and buildings and improvements, gross	79,198
Accumulated depreciation	$ 20,013
Depreciation life	35 years
Rentable square feet | ft²	169,412
320 Westlake Avenue North, WA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 14,710
Initial cost, buildings and Improvements	82,018
Costs capitalized subsequent to acquisition/ improvement	14,453
Land and improvements, gross	14,710
Buildings and improvements, gross	96,471
Land and improvements and buildings and improvements, gross	111,181
Accumulated depreciation	$ 23,304
Depreciation life	35 years
Rentable square feet | ft²	184,644
321 Terry Avenue North, Lake Union, WA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 10,430
Initial cost, buildings and Improvements	60,003
Costs capitalized subsequent to acquisition/ improvement	10,366
Land and improvements, gross	10,430
Buildings and improvements, gross	70,369
Land and improvements and buildings and improvements, gross	80,799
Accumulated depreciation	$ 18,091
Depreciation life	35 years
Rentable square feet | ft²	135,755
401 Terry Avenue North, Lake Union, WA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 22,500
Initial cost, buildings and Improvements	77,046
Costs capitalized subsequent to acquisition/ improvement	13
Land and improvements, gross	22,500
Buildings and improvements, gross	77,059
Land and improvements and buildings and improvements, gross	99,559
Accumulated depreciation	$ 18,225
Depreciation life	35 years
Rentable square feet | ft²	140,605
333 Dexter Ave. North, South Lake Union, WA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 0
Initial cost, buildings and Improvements	0
Costs capitalized subsequent to acquisition/ improvement	323,433
Land and improvements, gross	42,853
Buildings and improvements, gross	280,580
Land and improvements and buildings and improvements, gross	323,433
Accumulated depreciation	$ 2,592
Depreciation life	35 years
Rentable square feet | ft²	0
3200 Paseo Village Way, Del Mar, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, land and improvements	$ 106,419
Initial cost, buildings and Improvements	0
Costs capitalized subsequent to acquisition/ improvement	272,457
Land and improvements, gross	106,419
Buildings and improvements, gross	272,457
Land and improvements and buildings and improvements, gross	378,876
Accumulated depreciation	$ 7,316
Depreciation life	35 years
Rentable square feet | ft²	0
Operating Properties [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, encumbrances	$ 254,365
Initial cost, land and improvements	1,496,855
Initial cost, buildings and Improvements	2,699,959
Costs capitalized subsequent to acquisition/ improvement	4,215,126
Land and improvements, gross	1,628,848
Buildings and improvements, gross	6,783,092
Land and improvements and buildings and improvements, gross	8,411,940
Accumulated depreciation	$ 1,798,646
Rentable square feet | ft²	14,620,166
Office Building [Member] | W. Olympic Blvd., Los Angeles, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, encumbrances	$ 166,776
Office Building [Member] | 320 Westlake Ave. North, WA and 321 Terry Avenue North, Lake Union, WA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, encumbrances	87,589
Undeveloped land and construction in progress [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, encumbrances	0
Initial cost, land and improvements	874,773
Initial cost, buildings and Improvements	0
Costs capitalized subsequent to acquisition/ improvement	903,333
Land and improvements, gross	874,773
Buildings and improvements, gross	903,333
Land and improvements and buildings and improvements, gross	1,778,106
Accumulated depreciation	$ 0
Rentable square feet | ft²	0

Schedule III - Real Estate an_3

Schedule III - Real Estate and Accumulated Depreciation - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)ft²propertyproject
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, encumbrances | $	$ 254,365
Rentable square feet	14,620,166
Investment in real estate, federal Income tax basis | $	$ 8,600,000
In-process development projects - under construction [Member]
Real Estate and Accumulated Depreciation [Line Items]
Number of buildings | project	3
Rentable square feet	856,000
Sunset Blvd., Gower St. and El Centro Ave. Properties in Los Angeles [Member]
Real Estate and Accumulated Depreciation [Line Items]
Number of buildings | property	6
1550 N. El Centro Avenue, Los Angeles, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Depreciation life	35 years
Number of Units | property	200
Rentable square feet	0
3200 Paseo Village Way, San Diego, CA (Resi Phase I) (16) [Member]
Real Estate and Accumulated Depreciation [Line Items]
Number of Units | property	608
333 Dexter Ave. North, South Lake Union, WA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Depreciation life	35 years
Rentable square feet	0
Office Building [Member]
Real Estate and Accumulated Depreciation [Line Items]
Unamortized debt issuance expense | $	$ (800)
Office Building [Member] | Sunset Blvd., Gower St. and El Centro Ave. Properties in Los Angeles [Member]
Real Estate and Accumulated Depreciation [Line Items]
Number of buildings | property	5
Office Building [Member] | W. Olympic Blvd., Los Angeles, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, encumbrances | $	$ 166,776
Office Building [Member] | 320 Westlake Ave. North, WA and 321 Terry Avenue North, Lake Union, WA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Initial cost, encumbrances | $	$ 87,589
Residential Tower [Member] | Sunset Blvd., Gower St. and El Centro Ave. Properties in Los Angeles [Member]
Real Estate and Accumulated Depreciation [Line Items]
Number of buildings | property	1
Building [Member]
Real Estate and Accumulated Depreciation [Line Items]
Depreciation life	35 years
Tenant Improvements [Member] | Office Building [Member] | 12860 and 12830 El Camino Real, Del Mar, CA [Member] | In-process development projects - under construction [Member]
Real Estate and Accumulated Depreciation [Line Items]
Rentable square feet	285,000
Tenant Improvements [Member] | Office Building [Member] | 333 Dexter Ave. North, South Lake Union, WA [Member] | In-process development projects - under construction [Member]
Real Estate and Accumulated Depreciation [Line Items]
Rentable square feet	635,000
Tenant Improvements [Member] | Minimum [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property depreciable lives	1 year
Tenant Improvements [Member] | Maximum [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property depreciable lives	20 years

Schedule III - Real Estate an_4

Schedule III - Real Estate and Accumulated Depreciation - Historical Cost Real Estate Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate [Roll Forward]
Total real estate held for investment, beginning of year	$ 9,628,773	$ 8,426,632	$ 7,417,777
Acquisitions	0	460,512	581,671
Improvements, etc.	645,170	890,654	724,016
Total additions during period	645,170	1,351,166	1,305,687
Cost of real estate sold	(44,070)	(120,788)	(286,623)
Other	(39,827)	(28,237)	(10,209)
Total deductions during period	(83,897)	(149,025)	(296,832)
Total real estate held for investment, end of year	$ 10,190,046	$ 9,628,773	$ 8,426,632

Schedule III - Real Estate an_5

Schedule III - Real Estate and Accumulated Depreciation - Accumulated Depreciation Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Accumulated Depreciation [Roll Forward]
Accumulated depreciation, beginning of year	$ 1,561,361	$ 1,391,368	$ 1,264,162
Depreciation of real estate	244,815	211,893	198,578
Total additions during period	244,815	211,893	198,578
Write-offs due to sale	(6,401)	(41,655)	(71,372)
Other	(1,129)	(245)	0
Total deductions during period	(7,530)	(41,900)	(71,372)
Accumulated depreciation, end of year	$ 1,798,646	$ 1,561,361	$ 1,391,368