Kilroy Realty (KRC) 10-Q 29 Apr 21 2021 Q1 Quarterly report Financial data

Cover Page

Cover Page - shares	3 Months Ended
	Mar. 31, 2021	Apr. 23, 2021
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2021
Document Transition Report	false
Entity File Number	1-12675
Entity Registrant Name	KILROY REALTY CORPORATION
Entity Incorporation, State 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 Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		116,450,370
Entity Central Index Key	0001025996
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Amendment Flag	false
Kilroy Realty L.P. [Member]
Entity Information [Line Items]
Entity File Number	000-54005
Entity Registrant Name	KILROY REALTY, L.P.
Entity Incorporation, State Code	DE
Entity Tax Identification Number	95-4612685
Title of 12(g) Security	Common Units Representing Limited Partnership Interests
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Entity Central Index Key	0001493976

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
REAL ESTATE ASSETS (Note 2):
Land and improvements	$ 1,539,542	$ 1,628,848
Buildings and improvements	6,480,857	6,783,092
Undeveloped land and construction in progress	1,771,762	1,778,106
Total real estate assets held for investment	9,792,161	10,190,046
Accumulated depreciation and amortization	(1,838,338)	(1,798,646)
Total real estate assets held for investment, net	7,953,823	8,391,400
CASH AND CASH EQUIVALENTS	657,819	731,991
RESTRICTED CASH (Note 2)	1,028,759	91,139
MARKETABLE SECURITIES (Note 11)	24,089	27,481
CURRENT RECEIVABLES, NET	12,855	12,007
DEFERRED RENT RECEIVABLES, NET	370,470	386,658
DEFERRED LEASING COSTS AND ACQUISITION-RELATED INTANGIBLE ASSETS, NET	190,721	210,949
RIGHT OF USE GROUND LEASE ASSETS (Note 10)	95,312	95,523
PREPAID EXPENSES AND OTHER ASSETS, NET (Note 3)	50,505	53,560
TOTAL ASSETS	10,384,353	10,000,708
LIABILITIES:
Secured debt, net (Notes 4 and 11)	252,298	253,582
Unsecured debt, net (Notes 4 and 11)	3,671,094	3,670,099
Accounts payable, accrued expenses and other liabilities	408,552	445,100
Ground lease liabilities (Note 10)	97,617	97,778
Accrued dividends and distributions (Note 16)	59,472	59,431
Deferred revenue and acquisition-related intangible liabilities, net	123,794	128,523
Rents received in advance and tenant security deposits	68,634	68,874
Total liabilities	4,681,461	4,723,387
COMMITMENTS AND CONTINGENCIES (Note 10)
Stockholders’ Equity (Note 5):
Common stock, $.01 par value, 280,000,000 shares authorized, 116,450,370 and 116,035,827 shares issued and outstanding, respectively	1,165	1,160
Additional paid-in capital	5,122,584	5,131,916
Retained earnings (distributions in excess of earnings)	334,496	(103,133)
Total stockholders’ equity	5,458,245	5,029,943
Noncontrolling Interests (Notes 1 and 6):
Common units of the Operating Partnership	53,930	49,875
Noncontrolling interests in consolidated property partnerships	190,717	197,503
Total noncontrolling interests	244,647	247,378
Total equity	5,702,892	5,277,321
TOTAL LIABILITIES AND EQUITY (CAPITAL)	10,384,353	10,000,708
Kilroy Realty L.P. [Member]
REAL ESTATE ASSETS (Note 2):
Land and improvements	1,539,542	1,628,848
Buildings and improvements	6,480,857	6,783,092
Undeveloped land and construction in progress	1,771,762	1,778,106
Total real estate assets held for investment	9,792,161	10,190,046
Accumulated depreciation and amortization	(1,838,338)	(1,798,646)
Total real estate assets held for investment, net	7,953,823	8,391,400
CASH AND CASH EQUIVALENTS	657,819	731,991
RESTRICTED CASH (Note 2)	1,028,759	91,139
MARKETABLE SECURITIES (Note 11)	24,089	27,481
CURRENT RECEIVABLES, NET	12,855	12,007
DEFERRED RENT RECEIVABLES, NET	370,470	386,658
DEFERRED LEASING COSTS AND ACQUISITION-RELATED INTANGIBLE ASSETS, NET	190,721	210,949
RIGHT OF USE GROUND LEASE ASSETS (Note 10)	95,312	95,523
PREPAID EXPENSES AND OTHER ASSETS, NET (Note 3)	50,505	53,560
TOTAL ASSETS	10,384,353	10,000,708
LIABILITIES:
Secured debt, net (Notes 4 and 11)	252,298	253,582
Unsecured debt, net (Notes 4 and 11)	3,671,094	3,670,099
Accounts payable, accrued expenses and other liabilities	408,552	445,100
Ground lease liabilities (Note 10)	97,617	97,778
Accrued dividends and distributions (Note 16)	59,472	59,431
Deferred revenue and acquisition-related intangible liabilities, net	123,794	128,523
Rents received in advance and tenant security deposits	68,634	68,874
Total liabilities	4,681,461	4,723,387
COMMITMENTS AND CONTINGENCIES (Note 10)
Noncontrolling Interests (Notes 1 and 6):
Common units, 116,450,370 and 116,035,827 held by the general partner and 1,150,574 and 1,150,574 held by common limited partners issued and outstanding, respectively (Note 7)	5,512,175	5,079,818
Noncontrolling interests in consolidated property partnerships (Note 1)	190,717	197,503
Total capital	5,702,892	5,277,321
TOTAL LIABILITIES AND EQUITY (CAPITAL)	$ 10,384,353	$ 10,000,708

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Mar. 31, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	280,000,000	280,000,000
Common stock, shares issued (in shares)	116,450,370	116,035,827
Common stock, shares outstanding (in shares)	116,450,370	116,035,827
Common units [Member] | Kilroy Realty L.P. [Member]
General partner, units issued	116,450,370	116,035,827
General partners, units outstanding	116,450,370	116,035,827
Limited partners, units issued	1,150,574	1,150,574
Limited partners, units outstanding	1,150,574	1,150,574

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Revenue, Product and Service [Extensible List]	us-gaap:ServiceMember	us-gaap:ServiceMember
REVENUES
Rental income (Note 9)	$ 234,656	$ 218,633
Other property income	990	2,695
Total revenues	235,646	221,328
EXPENSES
Property expenses	38,859	38,983
Real estate taxes	25,266	22,202
Ground leases (Note 10)	1,828	2,317
General and administrative expenses (Note 8)	21,985	19,010
Leasing costs	692	1,456
Depreciation and amortization	75,932	74,370
Total expenses	164,562	158,338
OTHER INCOME (EXPENSES)
Interest income and other net investment gain (loss) (Note 11)	1,373	(3,128)
Interest expense (Note 4)	(22,334)	(14,444)
Gain on sale of depreciable operating property (Note 2)	457,288	0
Total other income (expenses)	436,327	(17,572)
NET INCOME	507,411	45,418
Net income attributable to noncontrolling common units of the Operating Partnership	(4,886)	(705)
Net income attributable to noncontrolling interests in consolidated property partnerships	(4,894)	(4,896)
Total income attributable to noncontrolling interests	(9,780)	(5,601)
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS (UNITHOLDERS)	$ 497,631	$ 39,817
Net income available to common stockholders per share – basic (in dollars per share)	$ 4.27	$ 0.37
Net income available to common stockholders per share – diluted (in dollars per share)	$ 4.26	$ 0.37
Weighted average common shares outstanding – basic (in shares)	116,344,375	106,875,234
Weighted average common shares outstanding – diluted (in shares)	116,801,384	107,389,575
Kilroy Realty L.P. [Member]
Revenue, Product and Service [Extensible List]	us-gaap:ServiceMember	us-gaap:ServiceMember
REVENUES
Rental income (Note 9)	$ 234,656	$ 218,633
Other property income	990	2,695
Total revenues	235,646	221,328
EXPENSES
Property expenses	38,859	38,983
Real estate taxes	25,266	22,202
Ground leases (Note 10)	1,828	2,317
General and administrative expenses (Note 8)	21,985	19,010
Leasing costs	692	1,456
Depreciation and amortization	75,932	74,370
Total expenses	164,562	158,338
OTHER INCOME (EXPENSES)
Interest income and other net investment gain (loss) (Note 11)	1,373	(3,128)
Interest expense (Note 4)	(22,334)	(14,444)
Gain on sale of depreciable operating property (Note 2)	457,288	0
Total other income (expenses)	436,327	(17,572)
NET INCOME	507,411	45,418
Total income attributable to noncontrolling interests	(4,894)	(5,029)
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS (UNITHOLDERS)	$ 502,517	$ 40,389
Net income available to common stockholders per share – basic (in dollars per share)	$ 4.27	$ 0.37
Net income available to common stockholders per share – diluted (in dollars per share)	$ 4.26	$ 0.36
Weighted average common shares outstanding – basic (in shares)	117,494,949	108,897,027
Weighted average common shares outstanding – diluted (in shares)	117,951,958	109,411,368

CONSOLIDATED STATEMENTS OF EQUI

CONSOLIDATED STATEMENTS OF EQUITY - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings (Distributions in Excess of Earnings) [Member]	Total Stockholders' Equity [Member]	Noncontrolling Interests [Member]
Beginning balance (in shares) at Dec. 31, 2019		106,016,287
Beginning balance at Dec. 31, 2019	$ 4,570,858	$ 1,060	$ 4,350,917	$ (58,467)	$ 4,293,510	$ 277,348
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	45,418			39,817	39,817	5,601
Issuance of common stock (in shares)		8,897,110
Issuance of common stock	721,794	$ 89	721,705		721,794
Issuance of share-based compensation awards	1,720		1,720		1,720
Non-cash amortization of share-based compensation (Note 8)	8,653		8,653		8,653
Settlement of restricted stock units for shares of common stock (in shares)		269,972
Settlement of restricted stock units for shares of common stock	0	$ 3	(3)
Repurchase of common stock, stock options and restricted stock units (in shares)		(117,445)
Repurchase of common stock, stock options and restricted stock units	(9,799)	$ (1)	(9,798)		(9,799)
Exchange of common units of the Operating Partnership (in shares)		2,000
Exchange of common units of the Operating Partnership	0	$ 0	81		81	(81)
Distributions to noncontrolling interests in consolidated property partnerships	(2,617)					(2,617)
Adjustment for noncontrolling interest	0		(6,094)		(6,094)	6,094
Dividends declared per common share and common unit	(58,512)			(57,532)	(57,532)	(980)
Ending balance (in shares) at Mar. 31, 2020		115,067,924
Ending balance at Mar. 31, 2020	$ 5,277,515	$ 1,151	5,067,181	(76,182)	4,992,150	285,365
Beginning balance (in shares) at Dec. 31, 2020	116,035,827	116,035,827
Beginning balance at Dec. 31, 2020	$ 5,277,321	$ 1,160	5,131,916	(103,133)	5,029,943	247,378
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	507,411			497,631	497,631	9,780
Issuance of share-based compensation awards	1,950		1,950		1,950
Non-cash amortization of share-based compensation (Note 8)	9,604		9,604		9,604
Settlement of restricted stock units for shares of common stock (in shares)		769,701
Settlement of restricted stock units for shares of common stock	0	$ 8	(8)
Repurchase of common stock, stock options and restricted stock units (in shares)		(355,158)
Repurchase of common stock, stock options and restricted stock units	(21,137)	$ (3)	(21,134)		(21,137)
Distributions to noncontrolling interests in consolidated property partnerships	(11,680)					(11,680)
Adjustment for noncontrolling interest	0		256		256	(256)
Dividends declared per common share and common unit	$ (60,577)			(60,002)	(60,002)	(575)
Ending balance (in shares) at Mar. 31, 2021	116,450,370	116,450,370
Ending balance at Mar. 31, 2021	$ 5,702,892	$ 1,165	$ 5,122,584	$ 334,496	$ 5,458,245	$ 244,647

CONSOLIDATED STATEMENTS OF EQ_2

CONSOLIDATED STATEMENTS OF EQUITY (Parenthetical) - $ / shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement of Stockholders' Equity [Abstract]
Dividends declared per common share and common unit (in dollars per share)	$ 0.500	$ 0.485

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 507,411	$ 45,418
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of real estate assets and leasing costs	74,431	72,438
Depreciation of non-real estate furniture, fixtures and equipment	1,501	1,932
Revenue reversals for doubtful accounts (Note 9)	1,035	6,487
Non-cash amortization of share-based compensation awards	7,877	6,783
Non-cash amortization of deferred financing costs and debt discounts and premiums	794	505
Non-cash amortization of net below market rents	(1,181)	(2,586)
Gain on sale of depreciable operating properties (Note 2)	(457,288)	0
Non-cash amortization of deferred revenue related to tenant-funded tenant improvements	(4,204)	(4,420)
Straight-line rents	(17,292)	(19,995)
Amortization of right of use ground lease assets	211	203
Net change in other operating assets	1,710	7,966
Net change in other operating liabilities	29,147	8,209
Net cash provided by operating activities	144,152	122,940
CASH FLOWS FROM INVESTING ACTIVITIES:
Expenditures for development properties and undeveloped land	(172,325)	(167,328)
Expenditures for operating properties and other capital assets	(28,242)	(44,084)
Net proceeds received from dispositions (Note 2)	1,012,817	0
Net cash provided by (used in) investing activities	812,250	(211,412)
CASH FLOWS FROM FINANCING ACTIVITIES:
Principal payments and repayments of secured debt	(1,316)	(1,266)
Financing costs	(235)	(160)
Repurchase of common stock and restricted stock units	(21,137)	(9,799)
Distributions to noncontrolling interests in consolidated property partnerships	(11,672)	(2,608)
Dividends and distributions paid to common stockholders and common unitholders	(58,594)	(52,399)
Net proceeds from issuance of common stock	0	721,794
Borrowings on unsecured revolving credit facility	0	190,000
Repayments on unsecured revolving credit facility	0	(55,000)
Net cash (used in) provided by financing activities	(92,954)	790,562
Net increase in cash and cash equivalents and restricted cash	863,448	702,090
Cash and cash equivalents and restricted cash, beginning of period	823,130	76,344
Cash and cash equivalents and restricted cash, end of period	1,686,578	778,434
Kilroy Realty L.P. [Member]
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	507,411	45,418
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of real estate assets and leasing costs	74,431	72,438
Depreciation of non-real estate furniture, fixtures and equipment	1,501	1,932
Revenue reversals for doubtful accounts (Note 9)	1,035	6,487
Non-cash amortization of share-based compensation awards	7,877	6,783
Non-cash amortization of deferred financing costs and debt discounts and premiums	794	505
Non-cash amortization of net below market rents	(1,181)	(2,586)
Gain on sale of depreciable operating properties (Note 2)	(457,288)	0
Non-cash amortization of deferred revenue related to tenant-funded tenant improvements	(4,204)	(4,420)
Straight-line rents	(17,292)	(19,995)
Amortization of right of use ground lease assets	211	203
Net change in other operating assets	1,710	7,966
Net change in other operating liabilities	29,147	8,209
Net cash provided by operating activities	144,152	122,940
CASH FLOWS FROM INVESTING ACTIVITIES:
Expenditures for development properties and undeveloped land	(172,325)	(167,328)
Expenditures for operating properties and other capital assets	(28,242)	(44,084)
Net proceeds received from dispositions (Note 2)	1,012,817	0
Net cash provided by (used in) investing activities	812,250	(211,412)
CASH FLOWS FROM FINANCING ACTIVITIES:
Principal payments and repayments of secured debt	(1,316)	(1,266)
Financing costs	(235)	(160)
Repurchase of common stock and restricted stock units	(21,137)	(9,799)
Distributions to noncontrolling interests in consolidated property partnerships	(11,672)	(2,608)
Dividends and distributions paid to common stockholders and common unitholders	(58,594)	(52,399)
Net proceeds from issuance of common stock	0	721,794
Borrowings on unsecured revolving credit facility	0	190,000
Repayments on unsecured revolving credit facility	0	(55,000)
Net cash (used in) provided by financing activities	(92,954)	790,562
Net increase in cash and cash equivalents and restricted cash	863,448	702,090
Cash and cash equivalents and restricted cash, beginning of period	823,130	76,344
Cash and cash equivalents and restricted cash, end of period	$ 1,686,578	$ 778,434

CONSOLIDATED STATEMENTS OF CAPI

CONSOLIDATED STATEMENTS OF CAPITAL (KILROY REALTY, L.P.) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income	$ 507,411	$ 45,418
Non-cash amortization of share-based compensation (Note 8)	9,604	8,653
Settlement of restricted stock units	0	0
Distributions to noncontrolling interests in consolidated property partnerships	(11,680)	(2,617)
Kilroy Realty L.P. [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning balance	5,277,321	4,570,858
Net income	507,411	45,418
Issuance of common units		721,794
Issuance of share-based compensation awards	1,950	1,720
Non-cash amortization of share-based compensation (Note 8)	9,604	8,653
Settlement of restricted stock units	0	0
Repurchase of common units, stock options and restricted stock units	(21,137)	(9,799)
Distributions to noncontrolling interests in consolidated property partnerships	(11,680)	(2,617)
Dividends declared per common unit	(60,577)	(58,512)
Ending balance	$ 5,702,892	$ 5,277,515
Partners' Capital [Member] | Kilroy Realty L.P. [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning balance (in units)	117,186,401	108,039,574
Beginning balance	$ 5,079,818	$ 4,369,758
Net income	502,517	$ 40,389
Issuance of common units (in units)		8,897,110
Issuance of common units		$ 721,794
Issuance of share-based compensation awards	1,950	1,720
Non-cash amortization of share-based compensation (Note 8)	$ 9,604	$ 8,653
Settlement of restricted stock units (in units)	769,701	269,972
Repurchase of common units, stock options and restricted stock units (in units)	(355,158)	(117,445)
Repurchase of common units, stock options and restricted stock units	$ (21,137)	$ (9,799)
Dividends declared per common unit	$ (60,577)	$ (58,512)
Ending balance (in units)	117,600,944	117,089,211
Ending balance	$ 5,512,175	$ 5,074,003
Noncontrolling Interests [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income	9,780	5,601
Distributions to noncontrolling interests in consolidated property partnerships	(11,680)	(2,617)
Noncontrolling Interests [Member] | Kilroy Realty L.P. [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
Beginning balance	197,503	201,100
Net income	4,894	5,029
Distributions to noncontrolling interests in consolidated property partnerships	(11,680)	(2,617)
Ending balance	$ 190,717	$ 203,512

CONSOLIDATED STATEMENTS OF CA_2

CONSOLIDATED STATEMENTS OF CAPITAL (KILROY REALTY, L.P.) (Parenthetical) - $ / shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Kilroy Realty L.P. [Member]
Dividends declared per common unit (in dollars per unit)	$ 0.500	$ 0.485

Organization, Ownership and Bas

Organization, Ownership and Basis of Presentation	3 Months Ended
	Mar. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization, Ownership and Basis of Presentation	Organization, Ownership and Basis of Presentation 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 March 31, 2021: Number of Rentable Number of Percentage Occupied (1) Percentage Leased Stabilized Office Properties (2) 117 14,049,585 436 91.5 % 93.3 % ________________________ (1) Represents physical and economic occupancy. (2) Includes stabilized life science and retail space. Number of Number of 2021 Average Occupancy Stabilized Residential Properties 2 808 69.1 % 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 three months ended March 31, 2021, we added one development project to our stabilized portfolio consisting of 160,444 square feet of office space in San Diego, California. As of March 31, 2021, the following properties were excluded from our stabilized portfolio. We did not have any redevelopment properties or properties held for sale at March 31, 2021. Number of Estimated Rentable Square Feet (1) In-process development projects - tenant improvement 3 1,576,000 In-process development projects - under construction (2) 2 200,000 ________________________ (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 March 31, 2021 was comprised of six future development sites, representing approximately 63 gross acres of undeveloped land. As of March 31, 2021, 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 March 31, 2021, 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 March 31, 2021, 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. Ownership and 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. As of March 31, 2021, 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 March 31, 2021 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. The accompanying interim financial statements have been prepared by management in accordance with accounting principles generally accepted in the United States of America (“GAAP”) and in conjunction with the rules and regulations of the Securities and Exchange Commission (“SEC”). Certain information and footnote disclosures required for annual financial statements have been condensed or excluded pursuant to SEC rules and regulations. Accordingly, the interim financial statements do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, the accompanying interim financial statements reflect all adjustments of a normal and recurring nature that are considered necessary for a fair presentation of the results for the interim periods presented. However, the results of operations for the interim periods are not necessarily indicative of the results that may be expected for the year ending December 31, 2021. The interim financial statements for the Company and the Operating Partnership should be read in conjunction with the audited consolidated financial statements and notes thereto included in our annual report on Form 10-K for the year ended December 31, 2020. Variable Interest Entities The Operating Partnership is a variable interest entity (“VIE”) that is consolidated by the Company as the primary beneficiary as the Operating Partnership is a limited partnership in which the common limited partners do not have substantive kick-out or participating rights. At March 31, 2021, the consolidated financial statements of the Company included two VIEs in addition to the Operating Partnership: 100 First LLC and 303 Second LLC. At March 31, 2021, 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 March 31, 2021, the two VIEs’ total assets, liabilities and noncontrolling interests included on our consolidated balance sheet were approximately $454.8 million (of which $389.9 million related to real estate held for investment), approximately $34.7 million and approximately $185.1 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, 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. At December 31, 2020, the impact of consolidating the VIEs increased the Company’s total assets, liabilities and noncontrolling interests on our consolidated balance sheet by 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. COVID-19 Pandemic The global impact of the COVID-19 pandemic continues to evolve rapidly and all 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. During the last few months, several vaccines for COVID-19 received emergency use authorization from the FDA and are currently being administered across the country. Despite growing vaccination rates, we believe COVID-19 will continue to impact the normal operations for our tenants. The continued impact of the pandemic on our business and our tenants’ businesses is largely dependent on efforts to stem the spread of COVID-19, including governmental efforts to distribute vaccines and overall vaccination rates in the areas in which we own properties and/or have development projects.

Dispositions

Dispositions	3 Months Ended
	Mar. 31, 2021
Discontinued Operations and Disposal Groups [Abstract]
Dispositions	Dispositions Operating Property Dispositions The following table summarizes the one operating property sold during the three months ended March 31, 2021: Property Month of Disposition Number of Buildings Rentable Square Feet Sales Price (in billions) (1) 1800 Owens Street, San Francisco, CA (The Exchange on 16th) March 1 750,370 $ 1.08 ___________________________ (1) Represents gross sales price before the impact of broker commissions and closing costs. The total gain on the sale of the operating property sold during the three months ended March 31, 2021 was $457.3 million. Restricted Cash Related to Dispositions

Prepaid Expenses and Other Asse

Prepaid Expenses and Other Assets, Net	3 Months Ended
	Mar. 31, 2021
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 March 31, 2021 and December 31, 2020: March 31, 2021 December 31, 2020 (in thousands) Furniture, fixtures and other long-lived assets, net $ 40,752 $ 43,367 Prepaid expenses and other assets, net 9,753 10,193 Total prepaid expenses and other assets, net $ 50,505 $ 53,560

Secured and Unsecured Debt of t

Secured and Unsecured Debt of the Operating Partnership	3 Months Ended
	Mar. 31, 2021
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 The Company generally guarantees all of the Operating Partnership’s unsecured debt obligations including the unsecured revolving credit facility and all of the unsecured senior notes. Unsecured Revolving Credit Facility The following table summarizes the balance and terms of our unsecured revolving credit facility as of March 31, 2021 and December 31, 2020: March 31, 2021 December 31, 2020 (in thousands) Outstanding borrowings $ — $ — Remaining borrowing capacity 750,000 750,000 Total borrowing capacity (1) $ 750,000 $ 750,000 Interest rate (2) 1.11 % 1.14 % 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. (2) Our unsecured revolving credit facility interest rate was calculated based on the contractual rate of LIBOR plus 1.000% as of March 31, 2021 and December 31, 2020. (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 March 31, 2021 and December 31, 2020, $1.7 million and $2.1 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 April 2021, the Operating Partnership amended and restated the terms of its unsecured revolving credit facility. The amendment and restatement increased the size of the unsecured revolving credit facility from $750.0 million to $1.1 billion, reduced the borrowing costs, extended the maturity date of the unsecured revolving credit facility to July 2025, with two six-month extension options, and added a sustainability-linked pricing component whereby the interest rate is lowered by 0.01% if certain sustainability performance targets are met. The LIBOR replacement provisions of the unsecured revolving credit facility permit the use of rates based on the secured overnight financing rate (“SOFR”) administered by the Federal Reserve Bank of New York. The unsecured revolving credit facility was undrawn at closing. 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, 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 March 31, 2021. Debt Maturities The following table summarizes the stated debt maturities and scheduled amortization payments as of March 31, 2021: Year (in thousands) Remaining 2021 $ 4,026 2022 5,554 2023 305,775 2024 431,006 2025 406,246 2026 401,317 Thereafter 2,399,125 Total aggregate principal value (1) $ 3,953,049 ________________________ (1) Includes gross principal balance of outstanding debt before the effect of the following at March 31, 2021: $21.7 million of unamortized deferred financing costs for the unsecured senior notes and secured debt and $8.0 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 three months ended March 31, 2021 and 2020. The interest expense capitalized was recorded as a cost of development and increased the carrying value of undeveloped land and construction in progress. Three Months Ended March 31, 2021 2020 (in thousands) Gross interest expense $ 39,242 $ 35,862 Capitalized interest and deferred financing costs (16,908) (21,418) Interest expense $ 22,334 $ 14,444

Stockholders' Equity of the Com

Stockholders' Equity of the Company	3 Months Ended
	Mar. 31, 2021
Equity [Abstract]
Stockholders' Equity of the Company	Stockholders’ Equity of the Company At-The-Market Stock Offering Program Under our at-the-market stock offering program, which commenced in June 2018, we may offer and sell shares of our common stock having an aggregate gross sales price up to $500.0 million from time to time in “at-the-market” offerings. In connection with our at-the-market program, the Company may enter into forward equity sale agreements with certain financial institutions acting as forward purchasers whereby, at our discretion, the forward purchasers may borrow and sell shares of our common stock under our at-the-market program. The use of a forward equity sale agreement allows the Company to lock in a share price on the sale of shares of our common stock at the time the agreement is executed but defer settling the forward equity sale agreements and receiving the proceeds from the sale of shares until a later date. The Company did not have any outstanding forward equity sale agreements to be settled at March 31, 2021. Since commencement of our current at-the-market program, we have completed sales of 3,594,576 shares of common stock through March 31, 2021. As of March 31, 2021, we may offer and sell shares of our common stock having an aggregate gross sales price up to approximately $214.2 million under our current at-the-market program. The Company did not complete any sales of common stock under the program during the three months ended March 31, 2021.

Noncontrolling Interests on the

Noncontrolling Interests on the Company's Consolidated Financial Statements	3 Months Ended
	Mar. 31, 2021
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 an approximate 99.0%, 99.0%, and 98.3% common general partnership interest in the Operating Partnership as of March 31, 2021, December 31, 2020 and March 31, 2020, respectively. The remaining approximate 1.0%, 1.0%, and 1.7% common limited partnership interest as of March 31, 2021, December 31, 2020 and March 31, 2020, 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, 1,150,574 and 2,021,287 common units outstanding held by these investors, executive officers and directors as of March 31, 2021, December 31, 2020 and March 31, 2020, respectively. 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 $76.6 million

Partners' Capital of the Operat

Partners' Capital of the Operating Partnership	3 Months Ended
	Mar. 31, 2021
Partners' Capital Notes [Abstract]
Partners’ Capital of the Operating Partnership	Partners’ Capital of the Operating Partnership 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: March 31, 2021 December 31, 2020 March 31, 2020 Company owned common units in the Operating Partnership 116,450,370 116,035,827 115,067,924 Company owned general partnership interest 99.0 % 99.0 % 98.3 % Noncontrolling common units of the Operating Partnership 1,150,574 1,150,574 2,021,287 Ownership interest of noncontrolling interest 1.0 % 1.0 % 1.7 % For further discussion of the noncontrolling common units as of March 31, 2021 and December 31, 2020, refer to Note 6.

Share-Based Compensation

Share-Based Compensation	3 Months Ended
	Mar. 31, 2021
Share-based Payment Arrangement [Abstract]
Share-Based Compensation	Share-Based Compensation Stockholder Approved Share-Based Incentive Compensation Plan As of March 31, 2021, 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 Plan. As of March 31, 2021, approximately 1.3 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. 2021 Share-Based Compensation Grants In January and February 2021, the Executive Compensation Committee of the Company’s Board of Directors awarded 332,707 restricted stock units (“RSUs”) to certain officers of the Company under the 2006 Plan, which included 172,430 RSUs (at the target level of performance) that are subject to market and/or performance-based vesting requirements (the “2021 Performance-Based RSUs”) and 160,277 RSUs that are subject to time-based vesting requirements (the “2021 Time-Based RSUs”). 2021 Performance-Based RSU Grant The 2021 Performance-Based RSUs are scheduled to vest at the end of a three year period (consisting of calendar years 2021-2023). A target number of 2021 Performance-Based RSUs were awarded, and the final number of 2021 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, 2021 that applies to 100% of the Performance-Based RSUs awarded (the “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 “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 “market condition”). The 2021 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 number of 2021 Performance-Based RSUs ultimately earned could fluctuate from the target number of 2021 Performance-Based RSUs granted based upon the levels of achievement for the FFO performance condition, the debt to EBITDA ratio performance condition, the market condition, and the extent to which the service vesting condition is satisfied. The estimate of the number of 2021 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. During the three months ended March 31, 2021, we recognized $1.0 million of compensation expense for the 2021 Performance-Based RSU grant. In the event we achieve a lower level of performance or fail to meet the FFO performance condition, we would reverse a portion or all of the $1.0 million of compensation expense. Compensation expense for the 2021 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 vesting period, except for one participant whose compensation expense is recognized on a rolling twelve-month basis. Each 2021 Performance-Based RSU represents the right, subject to the applicable vesting conditions, to receive one share of our common stock in the future. The determination of the grant date fair value of the portion of the 2021 Performance-Based RSU grants covered by the debt to EBITDA ratio performance condition was based on the $57.85 share price on the February 18, 2021 grant date. The determination of the grant date fair value of the portion of the 2021 Performance-Based RSU grants covered by the market condition was calculated using a Monte Carlo simulation pricing model based on the assumptions in the table below, which resulted in the following grant date fair value per share. Fair Value Assumptions Valuation date February 18, 2021 Expected share price volatility 35.0% Risk-free interest rate 0.20% Fair value per share on valuation date (1) $63.93 ________________________ (1) Using the same Monte Carlo methodology and assumptions, the grant date fair value of one participant’s 2021 Performance-Based RSU grants was calculated as $66.95 per share. The computation of expected volatility is based on a blend of the historical volatility of our shares of common stock over approximately 2.9 years, as that is expected to be most consistent with future volatility and equates to the approximate 2.9-year performance period of the RSUs, and implied volatility data based on the observed pricing of six month publicly-traded options on our shares of common stock. The risk-free interest rate is based on the yield curve on zero-coupon U.S. Treasury STRIP securities in effect at February 18, 2021. The total grant date fair value of the 2021 Performance-Based RSU awards was $10.6 million on the February 18, 2021 grant date of the awards. For the three months ended March 31, 2021, we recorded compensation expense based upon the grant date fair value per share for each component multiplied by the estimated number of RSUs to be earned. 2021 Time-Based RSU Grant The 2021 Time-Based RSUs are scheduled to vest in three equal annual installments beginning on January 5, 2022 through January 5, 2024. Compensation expense for the 2021 Time-Based RSUs is recognized on a straight-line basis over the requisite service period for each participant, which is generally the three year service vesting period, except for one participant whose compensation expense is recognized on a rolling twelve-month basis. Each 2021 Time-Based RSU represents the right to receive one share of our common stock in the future. The total grant date fair value of the 2021 Time-Based RSU awards was $9.1 million, which was based on the $56.63 and $57.85 closing share prices of the Company’s common stock on the NYSE on the January 29, 2021 and February 18, 2021 grant dates, respectively. 2020 and 2019 Performance-Based RSUs Compensation cost for the 2020 performance-based RSUs for the three months ended March 31, 2021 assumes the 2020 debt to EBITDA ratio performance condition is met at 125% of the target level of achievement (137.5% for one participant). Compensation cost for the 2019 performance-based RSUs for the three months ended March 31, 2021 assumes the 2019 debt to EBITDA ratio performance condition is met at the maximum level of achievement. Share-Based Compensation Cost Recorded During the Period The total compensation cost for all share-based compensation programs was $9.6 million and $8.7 million for the three months ended March 31, 2021 and 2020, respectively. Of the total share-based compensation costs, $1.7 million and $1.9 million was capitalized as part of real estate assets for the three months ended March 31, 2021 and 2020, respectively. As of March 31, 2021, there was approximately $47.2 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 1.6 years. The remaining compensation cost related to these nonvested incentive awards had been recognized in periods prior to March 31, 2021.

Rental Income and Future Minimu

Rental Income and Future Minimum Rent	3 Months Ended
	Mar. 31, 2021
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 collectability reversals for the three months ended March 31, 2021 and 2020: Three Months Ended March 31, 2021 2020 (in thousands) Fixed lease payments $ 204,216 $ 193,475 Variable lease payments 31,475 31,645 Collectability reversals (1) (1,035) (6,487) Total rental income $ 234,656 $ 218,633 _____________________ (1) Represents adjustments to rental income related to our assessment of the collectability of amounts due under leases with our tenants. For the three months ended March 31, 2021 and 2020, includes a reduction in revenue of $1.0 million and $6.5 million, respectively, primarily as a result of the COVID-19 pandemic. We have operating leases with tenants that expire at various dates through 2044. Generally, the leases grant tenants renewal options. 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 March 31, 2021 for future periods is summarized as follows: Year Ending (in thousands) Remaining 2021 $ 517,323 2022 759,071 2023 739,603 2024 699,571 2025 662,622 2026 609,838 Thereafter 2,334,046 Total (1) $ 6,322,074 _____________________ (1) Excludes residential leases and leases with a term of one year or less.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies General As of March 31, 2021, we had commitments of approximately $456.3 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 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. 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 March 31, 2021, the weighted average remaining lease term of our ground leases is 54 years. For the three months ended March 31, 2021 and 2020, variable lease costs totaling $0.4 million and $0.9 million, respectively, were recorded to ground lease expense on our consolidated statements of operations. The minimum commitment under our ground leases as of March 31, 2021 for future periods is summarized as follows: Year Ending (in thousands) Remaining 2021 $ 4,230 2022 5,642 2023 5,662 2024 5,662 2025 5,662 2026 5,662 Thereafter 275,062 Total undiscounted cash flows (1)(2)(3)(4)(5)(6) 307,582 Present value discount (209,965) Ground lease liabilities $ 97,617 ________________________ (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 March 31, 2021. (3) One of our ground lease obligations includes a component that 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 March 31, 2021 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 March 31, 2021 for the remainder of the lease term since we cannot predict future adjustments. (5) One of our ground lease obligations includes a component that is based on the percentage of adjusted gross income that exceeds the minimum ground rent. The minimum rent is subject to increases every ten 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 March 31, 2021 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 March 31, 2021, we had accrued environmental remediation liabilities of approximately $72.3 million 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 March 31, 2021 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.

Fair Value Measurements and Dis

Fair Value Measurements and Disclosures	3 Months Ended
	Mar. 31, 2021
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. The following table sets forth the fair value of our marketable securities as of March 31, 2021 and December 31, 2020: Fair Value (Level 1) (1) March 31, 2021 December 31, 2020 Description (in thousands) Marketable securities (2) $ 24,089 $ 27,481 ________________________ (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 three months ended March 31, 2021 and 2020: Three Months Ended March 31, 2021 2020 Description (in thousands) Net gain (loss) on marketable securities $ 1,305 $ (3,226) 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 March 31, 2021 and December 31, 2020: March 31, 2021 December 31, 2020 Carrying Fair (1) Carrying Fair (1) (in thousands) Liabilities Secured debt, net $ 252,298 $ 272,050 $ 253,582 $ 282,559 Unsecured debt, net $ 3,671,094 $ 3,931,186 $ 3,670,099 $ 4,089,339 ________________________ (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	3 Months Ended
	Mar. 31, 2021
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 three months ended March 31, 2021 and 2020: Three Months Ended March 31, 2021 2020 (in thousands, except share and per share amounts) Numerator: Net income available to common stockholders $ 497,631 $ 39,817 Allocation to participating securities (1) (365) (543) Numerator for basic and diluted net income available to common stockholders $ 497,266 $ 39,274 Denominator: Basic weighted average vested shares outstanding 116,344,375 106,875,234 Effect of dilutive securities 457,009 514,341 Diluted weighted average vested shares and common stock equivalents outstanding 116,801,384 107,389,575 Basic earnings per share: Net income available to common stockholders per share $ 4.27 $ 0.37 Diluted earnings per share: Net income available to common stockholders per share $ 4.26 $ 0.37 ________________________ (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 and other securities are considered in our diluted earnings per share calculation for the three months ended March 31, 2021 and 2020. Certain market measure-based RSUs are not included in dilutive securities for the three months ended March 31, 2021 and 2020, as not all performance metrics had been met by the end of the applicable reporting periods. See Note 8 “Share-Based Compensation” for additional information regarding share-based compensation.

Net Income Available to Commo_2

Net Income Available to Common Unitholders Per Unit of the Operating Partnership	3 Months Ended
	Mar. 31, 2021
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 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 three months ended March 31, 2021 and 2020: Three Months Ended March 31, 2021 2020 (in thousands, except share and per share amounts) Numerator: Net income available to common stockholders $ 497,631 $ 39,817 Allocation to participating securities (1) (365) (543) Numerator for basic and diluted net income available to common stockholders $ 497,266 $ 39,274 Denominator: Basic weighted average vested shares outstanding 116,344,375 106,875,234 Effect of dilutive securities 457,009 514,341 Diluted weighted average vested shares and common stock equivalents outstanding 116,801,384 107,389,575 Basic earnings per share: Net income available to common stockholders per share $ 4.27 $ 0.37 Diluted earnings per share: Net income available to common stockholders per share $ 4.26 $ 0.37 ________________________ (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 and other securities are considered in our diluted earnings per share calculation for the three months ended March 31, 2021 and 2020. Certain market measure-based RSUs are not included in dilutive securities for the three months ended March 31, 2021 and 2020, as not all performance metrics had been met by the end of the applicable reporting periods. See Note 8 “Share-Based Compensation” for additional information regarding share-based compensation.
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 three months ended March 31, 2021 and 2020: Three Months Ended March 31, 2021 2020 (in thousands, except unit and per unit amounts) Numerator: Net income available to common unitholders $ 502,517 $ 40,389 Allocation to participating securities (1) (365) (543) Numerator for basic and diluted net income available to common unitholders $ 502,152 $ 39,846 Denominator: Basic weighted average vested units outstanding 117,494,949 108,897,027 Effect of dilutive securities 457,009 514,341 Diluted weighted average vested units and common unit equivalents outstanding 117,951,958 109,411,368 Basic earnings per unit: Net income available to common unitholders per unit $ 4.27 $ 0.37 Diluted earnings per unit: Net income available to common unitholders per unit $ 4.26 $ 0.36 ________________________ (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 and other securities are considered in our diluted earnings per share calculation for the three months ended March 31, 2021 and 2020. Certain market measure-based RSUs are not included in dilutive securities for the three months ended March 31, 2021 and 2020, as not all performance metrics had been met by the end of the applicable reporting periods. See Note 8 “Share-Based Compensation” for additional information regarding share-based compensation.

Supplemental Cash Flow Informat

Supplemental Cash Flow Information of the Company	3 Months Ended
	Mar. 31, 2021
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): Three Months Ended March 31, 2021 2020 SUPPLEMENTAL CASH FLOWS INFORMATION: Cash paid for interest, net of capitalized interest of $16,131 and $20,403 as of March 31, 2021 and 2020, respectively $ 12,387 $ 10,035 Cash paid for amounts included in the measurement of ground lease liabilities $ 1,455 $ 1,332 NON-CASH INVESTING TRANSACTIONS: Accrual for expenditures for operating properties and development properties $ 57,675 $ 129,251 Tenant improvements funded directly by tenants $ 2,570 $ 2,081 NON-CASH FINANCING TRANSACTIONS: Accrual of dividends and distributions payable to common stockholders and common unitholders (Note 16) $ 59,472 $ 57,620 Exchange of common units of the Operating Partnership into shares of the Company’s common stock $ — $ 81 The following is a reconciliation of our cash and cash equivalents and restricted cash at the beginning and end of the three months ended March 31, 2021 and 2020. Three Months Ended March 31, 2021 2020 (in thousands) RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH: Cash and cash equivalents at beginning of period $ 731,991 $ 60,044 Restricted cash at beginning of period 91,139 16,300 Cash and cash equivalents and restricted cash at beginning of period $ 823,130 $ 76,344 Cash and cash equivalents at end of period $ 657,819 $ 762,134 Restricted cash at end of period 1,028,759 16,300 Cash and cash equivalents and restricted cash at end of period $ 1,686,578 $ 778,434

Supplemental Cash Flow Inform_2

Supplemental Cash Flow Information of the Operating Partnership	3 Months Ended
	Mar. 31, 2021
Other Significant Noncash Transactions [Line Items]
Supplemental Cash Flow Information of the Operating Partnership	Supplemental Cash Flow Information of the Company Supplemental cash flow information follows (in thousands): Three Months Ended March 31, 2021 2020 SUPPLEMENTAL CASH FLOWS INFORMATION: Cash paid for interest, net of capitalized interest of $16,131 and $20,403 as of March 31, 2021 and 2020, respectively $ 12,387 $ 10,035 Cash paid for amounts included in the measurement of ground lease liabilities $ 1,455 $ 1,332 NON-CASH INVESTING TRANSACTIONS: Accrual for expenditures for operating properties and development properties $ 57,675 $ 129,251 Tenant improvements funded directly by tenants $ 2,570 $ 2,081 NON-CASH FINANCING TRANSACTIONS: Accrual of dividends and distributions payable to common stockholders and common unitholders (Note 16) $ 59,472 $ 57,620 Exchange of common units of the Operating Partnership into shares of the Company’s common stock $ — $ 81 The following is a reconciliation of our cash and cash equivalents and restricted cash at the beginning and end of the three months ended March 31, 2021 and 2020. Three Months Ended March 31, 2021 2020 (in thousands) RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH: Cash and cash equivalents at beginning of period $ 731,991 $ 60,044 Restricted cash at beginning of period 91,139 16,300 Cash and cash equivalents and restricted cash at beginning of period $ 823,130 $ 76,344 Cash and cash equivalents at end of period $ 657,819 $ 762,134 Restricted cash at end of period 1,028,759 16,300 Cash and cash equivalents and restricted cash at end of period $ 1,686,578 $ 778,434
Kilroy Realty L.P. [Member]
Other Significant Noncash Transactions [Line Items]
Supplemental Cash Flow Information of the Operating Partnership	Supplemental Cash Flow Information of the Operating Partnership: Supplemental cash flow information follows (in thousands): Three Months Ended March 31, 2021 2020 SUPPLEMENTAL CASH FLOWS INFORMATION: Cash paid for interest, net of capitalized interest of $16,131 and $20,403 as of March 31, 2021 and 2020, respectively $ 12,387 $ 10,035 Cash paid for amounts included in the measurement of ground lease liabilities $ 1,455 $ 1,332 NON-CASH INVESTING TRANSACTIONS: Accrual for expenditures for operating properties and development properties $ 57,675 $ 129,251 Tenant improvements funded directly by tenants $ 2,570 $ 2,081 NON-CASH FINANCING TRANSACTIONS: Accrual of distributions payable to common unitholders (Note 16) $ 59,472 $ 57,620 The following is a reconciliation of our cash and cash equivalents and restricted cash at the beginning and end of the three months ended March 31, 2021 and 2020. Three Months Ended March 31, 2021 2020 (in thousands) RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH: Cash and cash equivalents at beginning of period $ 731,991 $ 60,044 Restricted cash at beginning of period 91,139 16,300 Cash and cash equivalents and restricted cash at beginning of period $ 823,130 $ 76,344 Cash and cash equivalents at end of period $ 657,819 $ 762,134 Restricted cash at end of period 1,028,759 16,300 Cash and cash equivalents and restricted cash at end of period $ 1,686,578 $ 778,434

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2021
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On April 14, 2021, aggregate dividends, distributions and dividend equivalents of $59.4 million were paid to common stockholders, common unitholders and RSU holders of record on March 31, 2021.

Organization, Ownership and B_2

Organization, Ownership and Basis of Presentation (Policies)	3 Months Ended
	Mar. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Consolidation policy	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.
Basis of accounting	The accompanying interim financial statements have been prepared by management in accordance with accounting principles generally accepted in the United States of America (“GAAP”) and in conjunction with the rules and regulations of the Securities and Exchange Commission (“SEC”). Certain information and footnote disclosures required for annual financial statements have been condensed or excluded pursuant to SEC rules and regulations. Accordingly, the interim financial statements do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, the accompanying interim financial statements reflect all adjustments of a normal and recurring nature that are considered necessary for a fair presentation of the results for the interim periods presented. However, the results of operations for the interim periods are not necessarily indicative of the results that may be expected for the year ending December 31, 2021. The interim financial statements for the Company and the Operating Partnership should be read in conjunction with the audited consolidated financial statements and notes thereto included in our annual report on Form 10-K for the year ended December 31, 2020.
New accounting pronouncements	COVID-19 Pandemic The global impact of the COVID-19 pandemic continues to evolve rapidly and all 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. During the last few months, several vaccines for COVID-19 received emergency use authorization from the FDA and are currently being administered across the country. Despite growing vaccination rates, we believe COVID-19 will continue to impact the normal operations for our tenants. The continued impact of the pandemic on our business and our tenants’ businesses is largely dependent on efforts to stem the spread of COVID-19, including governmental efforts to distribute vaccines and overall vaccination rates in the areas in which we own properties and/or have development projects.

Organization, Ownership and B_3

Organization, Ownership and Basis of Presentation (Tables)	3 Months Ended
	Mar. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Summary of real estate properties	Our stabilized portfolio of operating properties was comprised of the following properties at March 31, 2021: Number of Rentable Number of Percentage Occupied (1) Percentage Leased Stabilized Office Properties (2) 117 14,049,585 436 91.5 % 93.3 % ________________________ (1) Represents physical and economic occupancy. (2) Includes stabilized life science and retail space. Number of Number of 2021 Average Occupancy Stabilized Residential Properties 2 808 69.1 % Number of Estimated Rentable Square Feet (1) In-process development projects - tenant improvement 3 1,576,000 In-process development projects - under construction (2) 2 200,000 ________________________ (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.

Dispositions (Tables)

Dispositions (Tables)	3 Months Ended
	Mar. 31, 2021
Discontinued Operations and Disposal Groups [Abstract]
Schedule of operating property dispositions	The following table summarizes the one operating property sold during the three months ended March 31, 2021: Property Month of Disposition Number of Buildings Rentable Square Feet Sales Price (in billions) (1) 1800 Owens Street, San Francisco, CA (The Exchange on 16th) March 1 750,370 $ 1.08 ___________________________

Prepaid Expenses and Other As_2

Prepaid Expenses and Other Assets, Net (Tables)	3 Months Ended
	Mar. 31, 2021
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 March 31, 2021 and December 31, 2020: March 31, 2021 December 31, 2020 (in thousands) Furniture, fixtures and other long-lived assets, net $ 40,752 $ 43,367 Prepaid expenses and other assets, net 9,753 10,193 Total prepaid expenses and other assets, net $ 50,505 $ 53,560

Secured and Unsecured Debt of_2

Secured and Unsecured Debt of the Operating Partnership (Tables) - Kilroy Realty L.P. [Member]	3 Months Ended
	Mar. 31, 2021
Debt Instrument [Line Items]
Unsecured revolving credit facility	The following table summarizes the balance and terms of our unsecured revolving credit facility as of March 31, 2021 and December 31, 2020: March 31, 2021 December 31, 2020 (in thousands) Outstanding borrowings $ — $ — Remaining borrowing capacity 750,000 750,000 Total borrowing capacity (1) $ 750,000 $ 750,000 Interest rate (2) 1.11 % 1.14 % 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. (2) Our unsecured revolving credit facility interest rate was calculated based on the contractual rate of LIBOR plus 1.000% as of March 31, 2021 and December 31, 2020. (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 March 31, 2021 and December 31, 2020, $1.7 million and $2.1 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.
Schedule of debt maturities	The following table summarizes the stated debt maturities and scheduled amortization payments as of March 31, 2021: Year (in thousands) Remaining 2021 $ 4,026 2022 5,554 2023 305,775 2024 431,006 2025 406,246 2026 401,317 Thereafter 2,399,125 Total aggregate principal value (1) $ 3,953,049 ________________________
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 three months ended March 31, 2021 and 2020. The interest expense capitalized was recorded as a cost of development and increased the carrying value of undeveloped land and construction in progress. Three Months Ended March 31, 2021 2020 (in thousands) Gross interest expense $ 39,242 $ 35,862 Capitalized interest and deferred financing costs (16,908) (21,418) Interest expense $ 22,334 $ 14,444

Partners' Capital of the Oper_2

Partners' Capital of the Operating Partnership (Tables)	3 Months Ended
	Mar. 31, 2021
Partners' Capital Notes [Abstract]
Schedule of 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: March 31, 2021 December 31, 2020 March 31, 2020 Company owned common units in the Operating Partnership 116,450,370 116,035,827 115,067,924 Company owned general partnership interest 99.0 % 99.0 % 98.3 % Noncontrolling common units of the Operating Partnership 1,150,574 1,150,574 2,021,287 Ownership interest of noncontrolling interest 1.0 % 1.0 % 1.7 %

Share-Based Compensation (Table

Share-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2021
Share-based Payment Arrangement [Abstract]
Schedule of share-based payment award, restricted stock units, valuation assumptions	The determination of the grant date fair value of the portion of the 2021 Performance-Based RSU grants covered by the market condition was calculated using a Monte Carlo simulation pricing model based on the assumptions in the table below, which resulted in the following grant date fair value per share. Fair Value Assumptions Valuation date February 18, 2021 Expected share price volatility 35.0% Risk-free interest rate 0.20% Fair value per share on valuation date (1) $63.93 ________________________ (1) Using the same Monte Carlo methodology and assumptions, the grant date fair value of one participant’s 2021 Performance-Based RSU grants was calculated as $66.95 per share.

Rental Income and Future Mini_2

Rental Income and Future Minimum Rent (Tables)	3 Months Ended
	Mar. 31, 2021
Leases [Abstract]
Rental income	The table below sets forth the allocation of rental income between fixed and variable payments and collectability reversals for the three months ended March 31, 2021 and 2020: Three Months Ended March 31, 2021 2020 (in thousands) Fixed lease payments $ 204,216 $ 193,475 Variable lease payments 31,475 31,645 Collectability reversals (1) (1,035) (6,487) Total rental income $ 234,656 $ 218,633 _____________________
Future contractual minimum rent under operating leases	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 March 31, 2021 for future periods is summarized as follows: Year Ending (in thousands) Remaining 2021 $ 517,323 2022 759,071 2023 739,603 2024 699,571 2025 662,622 2026 609,838 Thereafter 2,334,046 Total (1) $ 6,322,074 _____________________ (1) Excludes residential leases and leases with a term of one year or less.

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2021
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 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 future minimum rental repayments for ground leases	The minimum commitment under our ground leases as of March 31, 2021 for future periods is summarized as follows: Year Ending (in thousands) Remaining 2021 $ 4,230 2022 5,642 2023 5,662 2024 5,662 2025 5,662 2026 5,662 Thereafter 275,062 Total undiscounted cash flows (1)(2)(3)(4)(5)(6) 307,582 Present value discount (209,965) Ground lease liabilities $ 97,617 ________________________ (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 March 31, 2021. (3) One of our ground lease obligations includes a component that 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 March 31, 2021 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 March 31, 2021 for the remainder of the lease term since we cannot predict future adjustments. (5) One of our ground lease obligations includes a component that is based on the percentage of adjusted gross income that exceeds the minimum ground rent. The minimum rent is subject to increases every ten 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 March 31, 2021 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.

Fair Value Measurements and D_2

Fair Value Measurements and Disclosures (Tables)	3 Months Ended
	Mar. 31, 2021
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 March 31, 2021 and December 31, 2020: Fair Value (Level 1) (1) March 31, 2021 December 31, 2020 Description (in thousands) Marketable securities (2) $ 24,089 $ 27,481 ________________________ (1) Based on quoted prices in active markets for identical securities. (2) The marketable securities are held in a limited rabbi trust.
Net gain (loss) on marketable securities	The following table sets forth the net gain (loss) on marketable securities recorded during the three months ended March 31, 2021 and 2020: Three Months Ended March 31, 2021 2020 Description (in thousands) Net gain (loss) on marketable securities $ 1,305 $ (3,226)
Carrying value and fair value of company's remaining financial instruments	The following table sets forth the carrying value and the fair value of our other financial instruments as of March 31, 2021 and December 31, 2020: March 31, 2021 December 31, 2020 Carrying Fair (1) Carrying Fair (1) (in thousands) Liabilities Secured debt, net $ 252,298 $ 272,050 $ 253,582 $ 282,559 Unsecured debt, net $ 3,671,094 $ 3,931,186 $ 3,670,099 $ 4,089,339 ________________________ (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)	3 Months Ended
	Mar. 31, 2021
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 three months ended March 31, 2021 and 2020: Three Months Ended March 31, 2021 2020 (in thousands, except share and per share amounts) Numerator: Net income available to common stockholders $ 497,631 $ 39,817 Allocation to participating securities (1) (365) (543) Numerator for basic and diluted net income available to common stockholders $ 497,266 $ 39,274 Denominator: Basic weighted average vested shares outstanding 116,344,375 106,875,234 Effect of dilutive securities 457,009 514,341 Diluted weighted average vested shares and common stock equivalents outstanding 116,801,384 107,389,575 Basic earnings per share: Net income available to common stockholders per share $ 4.27 $ 0.37 Diluted earnings per share: Net income available to common stockholders per share $ 4.26 $ 0.37 ________________________

Net Income Available to Commo_4

Net Income Available to Common Unitholders Per Unit of the Operating Partnership (Tables)	3 Months Ended
	Mar. 31, 2021
Net Income Available To Common Unitholders [Line Items]
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 three months ended March 31, 2021 and 2020: Three Months Ended March 31, 2021 2020 (in thousands, except share and per share amounts) Numerator: Net income available to common stockholders $ 497,631 $ 39,817 Allocation to participating securities (1) (365) (543) Numerator for basic and diluted net income available to common stockholders $ 497,266 $ 39,274 Denominator: Basic weighted average vested shares outstanding 116,344,375 106,875,234 Effect of dilutive securities 457,009 514,341 Diluted weighted average vested shares and common stock equivalents outstanding 116,801,384 107,389,575 Basic earnings per share: Net income available to common stockholders per share $ 4.27 $ 0.37 Diluted earnings per share: Net income available to common stockholders per share $ 4.26 $ 0.37 ________________________
Kilroy Realty L.P. [Member]
Net Income Available To Common Unitholders [Line Items]
Net income available to common stockholders	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 three months ended March 31, 2021 and 2020: Three Months Ended March 31, 2021 2020 (in thousands, except unit and per unit amounts) Numerator: Net income available to common unitholders $ 502,517 $ 40,389 Allocation to participating securities (1) (365) (543) Numerator for basic and diluted net income available to common unitholders $ 502,152 $ 39,846 Denominator: Basic weighted average vested units outstanding 117,494,949 108,897,027 Effect of dilutive securities 457,009 514,341 Diluted weighted average vested units and common unit equivalents outstanding 117,951,958 109,411,368 Basic earnings per unit: Net income available to common unitholders per unit $ 4.27 $ 0.37 Diluted earnings per unit: Net income available to common unitholders per unit $ 4.26 $ 0.36 ________________________

Supplemental Cash Flow Inform_3

Supplemental Cash Flow Information of the Company (Tables)	3 Months Ended
	Mar. 31, 2021
Supplemental Cash Flow Elements [Abstract]
Schedule of supplemental cash flows	Supplemental cash flow information follows (in thousands): Three Months Ended March 31, 2021 2020 SUPPLEMENTAL CASH FLOWS INFORMATION: Cash paid for interest, net of capitalized interest of $16,131 and $20,403 as of March 31, 2021 and 2020, respectively $ 12,387 $ 10,035 Cash paid for amounts included in the measurement of ground lease liabilities $ 1,455 $ 1,332 NON-CASH INVESTING TRANSACTIONS: Accrual for expenditures for operating properties and development properties $ 57,675 $ 129,251 Tenant improvements funded directly by tenants $ 2,570 $ 2,081 NON-CASH FINANCING TRANSACTIONS: Accrual of dividends and distributions payable to common stockholders and common unitholders (Note 16) $ 59,472 $ 57,620 Exchange of common units of the Operating Partnership into shares of the Company’s common stock $ — $ 81
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 three months ended March 31, 2021 and 2020. Three Months Ended March 31, 2021 2020 (in thousands) RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH: Cash and cash equivalents at beginning of period $ 731,991 $ 60,044 Restricted cash at beginning of period 91,139 16,300 Cash and cash equivalents and restricted cash at beginning of period $ 823,130 $ 76,344 Cash and cash equivalents at end of period $ 657,819 $ 762,134 Restricted cash at end of period 1,028,759 16,300 Cash and cash equivalents and restricted cash at end of period $ 1,686,578 $ 778,434
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 three months ended March 31, 2021 and 2020. Three Months Ended March 31, 2021 2020 (in thousands) RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH: Cash and cash equivalents at beginning of period $ 731,991 $ 60,044 Restricted cash at beginning of period 91,139 16,300 Cash and cash equivalents and restricted cash at beginning of period $ 823,130 $ 76,344 Cash and cash equivalents at end of period $ 657,819 $ 762,134 Restricted cash at end of period 1,028,759 16,300 Cash and cash equivalents and restricted cash at end of period $ 1,686,578 $ 778,434

Supplemental Cash Flow Inform_4

Supplemental Cash Flow Information of the Operating Partnership (Tables)	3 Months Ended
	Mar. 31, 2021
Other Significant Noncash Transactions [Line Items]
Schedule of supplemental cash flows	Supplemental cash flow information follows (in thousands): Three Months Ended March 31, 2021 2020 SUPPLEMENTAL CASH FLOWS INFORMATION: Cash paid for interest, net of capitalized interest of $16,131 and $20,403 as of March 31, 2021 and 2020, respectively $ 12,387 $ 10,035 Cash paid for amounts included in the measurement of ground lease liabilities $ 1,455 $ 1,332 NON-CASH INVESTING TRANSACTIONS: Accrual for expenditures for operating properties and development properties $ 57,675 $ 129,251 Tenant improvements funded directly by tenants $ 2,570 $ 2,081 NON-CASH FINANCING TRANSACTIONS: Accrual of dividends and distributions payable to common stockholders and common unitholders (Note 16) $ 59,472 $ 57,620 Exchange of common units of the Operating Partnership into shares of the Company’s common stock $ — $ 81
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 three months ended March 31, 2021 and 2020. Three Months Ended March 31, 2021 2020 (in thousands) RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH: Cash and cash equivalents at beginning of period $ 731,991 $ 60,044 Restricted cash at beginning of period 91,139 16,300 Cash and cash equivalents and restricted cash at beginning of period $ 823,130 $ 76,344 Cash and cash equivalents at end of period $ 657,819 $ 762,134 Restricted cash at end of period 1,028,759 16,300 Cash and cash equivalents and restricted cash at end of period $ 1,686,578 $ 778,434
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 three months ended March 31, 2021 and 2020. Three Months Ended March 31, 2021 2020 (in thousands) RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH: Cash and cash equivalents at beginning of period $ 731,991 $ 60,044 Restricted cash at beginning of period 91,139 16,300 Cash and cash equivalents and restricted cash at beginning of period $ 823,130 $ 76,344 Cash and cash equivalents at end of period $ 657,819 $ 762,134 Restricted cash at end of period 1,028,759 16,300 Cash and cash equivalents and restricted cash at end of period $ 1,686,578 $ 778,434
Kilroy Realty L.P. [Member]
Other Significant Noncash Transactions [Line Items]
Schedule of supplemental cash flows	Supplemental cash flow information follows (in thousands): Three Months Ended March 31, 2021 2020 SUPPLEMENTAL CASH FLOWS INFORMATION: Cash paid for interest, net of capitalized interest of $16,131 and $20,403 as of March 31, 2021 and 2020, respectively $ 12,387 $ 10,035 Cash paid for amounts included in the measurement of ground lease liabilities $ 1,455 $ 1,332 NON-CASH INVESTING TRANSACTIONS: Accrual for expenditures for operating properties and development properties $ 57,675 $ 129,251 Tenant improvements funded directly by tenants $ 2,570 $ 2,081 NON-CASH FINANCING TRANSACTIONS: Accrual of distributions payable to common unitholders (Note 16) $ 59,472 $ 57,620
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 three months ended March 31, 2021 and 2020. Three Months Ended March 31, 2021 2020 (in thousands) RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH: Cash and cash equivalents at beginning of period $ 731,991 $ 60,044 Restricted cash at beginning of period 91,139 16,300 Cash and cash equivalents and restricted cash at beginning of period $ 823,130 $ 76,344 Cash and cash equivalents at end of period $ 657,819 $ 762,134 Restricted cash at end of period 1,028,759 16,300 Cash and cash equivalents and restricted cash at end of period $ 1,686,578 $ 778,434
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 three months ended March 31, 2021 and 2020. Three Months Ended March 31, 2021 2020 (in thousands) RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH: Cash and cash equivalents at beginning of period $ 731,991 $ 60,044 Restricted cash at beginning of period 91,139 16,300 Cash and cash equivalents and restricted cash at beginning of period $ 823,130 $ 76,344 Cash and cash equivalents at end of period $ 657,819 $ 762,134 Restricted cash at end of period 1,028,759 16,300 Cash and cash equivalents and restricted cash at end of period $ 1,686,578 $ 778,434

Organization, Ownership and B_4

Organization, Ownership and Basis of Presentation - Operating Properties (Details)	3 Months Ended
	Mar. 31, 2021ft²residential_unitprojectbuildingtenant
Stabilized office properties [Member]
Real Estate Properties [Line Items]
Number of Buildings | building	117
Rentable Square Feet | ft²	14,049,585
Number of Tenants | tenant	436
Percentage Occupied	91.50%
Percentage Leased	93.30%
Stabilized residential properties [Member]
Real Estate Properties [Line Items]
Number of Buildings | building	2
Number of Units | building	808
2021 Average Occupancy	69.10%
In-process development projects - tenant improvement [Member]
Real Estate Properties [Line Items]
Number of Buildings | project	3
Rentable Square Feet | ft²	1,576,000
In-process development projects - under construction [Member]
Real Estate Properties [Line Items]
Number of Buildings | project	2
Rentable Square Feet | ft²	200,000
Number of residential units | residential_unit	193

Organization, Ownership and B_5

Organization, Ownership and Basis of Presentation - Narrative (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2021USD ($)ft²apropertyVIEbuildingproperty_partnershipproject	Mar. 31, 2020	Dec. 31, 2020USD ($)VIE
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Lease-up properties occupancy percentage	95.00%
Lease-up properties occupancy duration	1 year
Assets	$ 10,384,353		$ 10,000,708
Liabilities	4,681,461		4,723,387
Noncontrolling interest in VIE	$ 190,717		$ 197,503
San Francisco, California [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of properties | building	1
Washington [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of properties | property	1
Stabilized office properties [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of properties | building	117
Rentable square feet | ft²	14,049,585
Stabilized office properties [Member] | Washington [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of properties | property	8
Development properties [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of property partnerships | property_partnership	3
Development properties [Member] | San Diego, California [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of properties | property	1
Rentable square feet | ft²	160,444
Development properties [Member] | Washington [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of properties | property	1
Office properties owned by consolidated property partnerships [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of properties | property	4
Development sites [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of properties | project	6
Area of undeveloped land | a	63
Properties and development projects [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Property ownership percentage	100.00%
101 First LLC and 303 Second LLC [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Company owned general partnership interest	56.00%
101 First LLC and 303 Second LLC [Member] | Development properties [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of property partnerships | property_partnership	2
Redwood LLC [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of properties | property	2
Company owned general partnership interest	93.00%
Operating Partnership [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Ownership interest (percent)	99.00%	98.30%	99.00%
Non-affiliated investors and certain of our executive officers and directors [Member] | Operating Partnership [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Ownership interest (percent)	1.00%	1.70%	1.00%
Variable Interest Entity, Primary Beneficiary [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of VIEs | VIE	2		2
Assets	$ 454,800		$ 469,300
Liabilities	34,700		33,900
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	389,900		394,600
Variable Interest Entity, Primary Beneficiary [Member] | 101 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 VIE	$ 185,100		$ 191,900

Dispositions and Real Estate He

Dispositions and Real Estate Held for Sale - Operating Property Dispositions (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)ft²building	Mar. 31, 2020USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gains on sales of operating properties	$ 457,288	$ 0
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Restricted cash	$ 1,000,000
Operating Properties [Member] | 1800 Owens Street, San Francisco, CA [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties | building	1
Rentable square feet | ft²	750,370
Sales price	$ 1,080,000
Gains on sales of operating properties	$ 457,300

Prepaid Expenses and Other As_3

Prepaid Expenses and Other Assets, Net (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Prepaid Expense and Other Assets [Abstract]
Furniture, fixtures and other long-lived assets, net	$ 40,752	$ 43,367
Prepaid expenses and other assets, net	9,753	10,193
Total prepaid expenses and other assets, net	$ 50,505	$ 53,560

Secured and Unsecured Debt of_3

Secured and Unsecured Debt of the Operating Partnership - Unsecured Senior Notes, Unsecured Revolving Credit Facility and Term Loan Facility (Details) - Kilroy Realty L.P. [Member] - Revolving credit facility [Member] - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Terms of the Credit Facility
Outstanding borrowings	$ 0	$ 0
Remaining borrowing capacity	750,000,000	750,000,000
Total borrowing capacity	$ 750,000,000	$ 750,000,000
Interest rate (percent)	1.11%	1.14%
Facility fee-annual rate (percent)	0.20%	0.20%
Contingent additional borrowings	$ 600,000,000
Unamortized deferred financing costs	$ 1,700,000	$ 2,100,000
London Interbank Offered Rate (LIBOR) [Member]
Terms of the Credit Facility
Variable rate (percent)	1.00%	1.00%

Secured and Unsecured Debt of_4

Secured and Unsecured Debt of the Operating Partnership - Additional Information (Details) - Kilroy Realty L.P. [Member] - Revolving credit facility [Member]	1 Months Ended
	Apr. 29, 2021USD ($)extensionOption	Mar. 31, 2021USD ($)	Dec. 31, 2020USD ($)
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 750,000,000	$ 750,000,000
Subsequent event [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 1,100,000,000
Interest rate reduction if sustainability performance targets met (percent)	0.01%
Number of extension options | extensionOption	2
Extension period	6 months

Secured and Unsecured Debt of_5

Secured and Unsecured Debt of the Operating Partnership - Debt Maturities (Details) - Kilroy Realty L.P. [Member] $ in Thousands	Mar. 31, 2021USD ($)
Stated debt maturities and scheduled amortization payments
Remaining 2021	$ 4,026
2022	5,554
2023	305,775
2024	431,006
2025	406,246
2026	401,317
Thereafter	2,399,125
Total debt	3,953,049
Unsecured term loan facility, unsecured senior notes and secured debt [Member]
Stated debt maturities and scheduled amortization payments
Unamortized deferred financing costs	21,700
Unsecured senior notes [Member]
Stated debt maturities and scheduled amortization payments
Unamortized discount	$ 8,000

Secured and Unsecured Debt of_6

Secured and Unsecured Debt of the Operating Partnership - Capitalized Interest and Loan Fees (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Capitalized Interest and Loan Fees [Line Items]
Interest expense	$ 22,334	$ 14,444
Kilroy Realty L.P. [Member]
Capitalized Interest and Loan Fees [Line Items]
Gross interest expense	39,242	35,862
Capitalized interest and deferred financing costs	(16,908)	(21,418)
Interest expense	$ 22,334	$ 14,444

Stockholders' Equity of the C_2

Stockholders' Equity of the Company (Details) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Jun. 30, 2018
Class of Stock [Line Items]
At the market stock offering aggregate gross sales price of common stock				$ 500,000,000
Common stock, shares issued (in shares)	116,450,370		116,035,827
Proceeds from issuance of stock	$ 0	$ 721,794,000
Common Stock [Member] | Forward equity sale [Member]
Class of Stock [Line Items]
Common stock, shares issued (in shares)	3,594,576
At the market stock offering remaining amount available for issuance	$ 214,200,000
Proceeds from issuance of stock	$ 0

Noncontrolling Interests on t_2

Noncontrolling Interests on the Company's Consolidated Financial Statements (Details) $ / shares in Units, $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2021USD ($)trading_day$ / sharesshares	Mar. 31, 2020shares	Dec. 31, 2020USD ($)$ / sharesshares
Noncontrolling Interest [Line Items]
Common stock, par value (in dollars per share) | $ / shares	$ 0.01		$ 0.01
Number of trading days | trading_day	10
Aggregate value upon redemption of outstanding noncontrolling common units | $	$ 76.6		$ 65.4
Non-affiliated investors and certain of our executive officers and directors [Member] | Common units [Member]
Noncontrolling Interest [Line Items]
Common units outstanding held by common limited partners (in units) | shares	1,150,574	2,021,287	1,150,574
Operating Partnership [Member]
Noncontrolling Interest [Line Items]
Ownership interest (percent)	99.00%	98.30%	99.00%
Operating Partnership [Member] | Non-affiliated investors and certain of our executive officers and directors [Member]
Noncontrolling Interest [Line Items]
Ownership interest (percent)	1.00%	1.70%	1.00%

Partners' Capital of the Oper_3

Partners' Capital of the Operating Partnership (Details) - shares	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Operating Partnership [Member]
General Partners' Capital Account [Abstract]
Ownership interest (percent)	99.00%	98.30%	99.00%
Kilroy Realty L.P. [Member] | Common units [Member]
General Partners' Capital Account [Abstract]
Company owned common units in the Operating Partnership (in units)	116,450,370	115,067,924	116,035,827
Noncontrolling common units of the Operating Partnership (in units)	1,150,574		1,150,574
Non-affiliated investors and certain of our executive officers and directors [Member] | Operating Partnership [Member]
General Partners' Capital Account [Abstract]
Ownership interest (percent)	1.00%	1.70%	1.00%
Non-affiliated investors and certain of our executive officers and directors [Member] | Common units [Member]
General Partners' Capital Account [Abstract]
Noncontrolling common units of the Operating Partnership (in units)	1,150,574	2,021,287	1,150,574

Share-Based Compensation - Narr

Share-Based Compensation - Narrative (Details) $ / shares in Units, $ in Millions	Feb. 18, 2021USD ($)$ / shares	Feb. 28, 2021USD ($)installmentparticipantshares	Mar. 31, 2021USD ($)compensation_planshares	Mar. 31, 2020USD ($)	Jan. 29, 2021$ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of share-based incentive compensation plans | compensation_plan			1
Effective registration shares (in shares) | shares			10,700,000
Number of shares available for grant (in shares) | shares			1,300,000
Share-based compensation expense | $			$ 9.6	$ 8.7
Share-based compensation expense capitalized | $			1.7	$ 1.9
Share-based compensation not yet recognized | $			$ 47.2
Share-based compensation not yet recognized period of recognition			1 year 7 months 6 days
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares granted in period (in shares) | shares		332,707
Market Measure-Based Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares granted in period (in shares) | shares		172,430
Time-Based Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares granted in period (in shares) | shares		160,277
Time-Based RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period		3 years
Number of participants with compensation expense recognized on a rolling twelve-month basis | participant		1
Number of installments | installment		3
Right to receive number of shares (in shares) | shares		1
Time-Based Restricted Stock Units (RSUs), Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value RSUs granted | $		$ 9.1
2021 Performance-Based RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period		3 years
Vesting, achievement of pre-set FFO per share goals, percentage of RSUs		100.00%
Vesting, Average debt to EBIDTA ratio, percentage of RSUs		50.00%
Vesting, Market measure, percentage of RSUs		50.00%
Number of shares issuable per RSU		1
Share price | $ / shares	$ 57.85				$ 56.63
Fair value per share on valuation date (in dollars per share) | $ / shares	$ 63.93
Remaining expected life, including future volatility		2 years 10 months 24 days
Performance period		2 years 10 months 24 days
Fair value RSUs granted | $	$ 10.6
Share-based compensation expense | $			$ 1
2020 Performance-Based RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance-based RSU, achievement target, all other participants, percent			125.00%
Performance-based RSU, achievement target, one participant, percent			137.50%

Share-Based Compensation - Fair

Share-Based Compensation - Fair Value Assumptions (Details) - 2021 Performance-Based RSUs [Member]	Feb. 18, 2021$ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected share price volatility	35.00%
Risk-free interest rate	0.20%
Fair value per share on valuation date (in dollars per share)	$ 63.93
One Participant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value per share on valuation date (in dollars per share)	$ 66.95

Rental Income and Future Mini_3

Rental Income and Future Minimum Rent - Rental income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Leases [Abstract]
Fixed lease payments	$ 204,216	$ 193,475
Variable lease payments	31,475	31,645
Collectability reversals	(1,035)	(6,487)
Total rental income	234,656	218,633
Reduction of revenue primarily as a result of the COVID-19 pandemic	$ (1,000)	$ (6,500)

Rental Income and Future Mini_4

Rental Income and Future Minimum Rent - Future Contractual Minimum Rent (Details) $ in Thousands	Mar. 31, 2021USD ($)
Future contractual minimum rent under operating lease
Remaining 2021	$ 517,323
2022	759,071
2023	739,603
2024	699,571
2025	662,622
2026	609,838
Thereafter	2,334,046
Total	$ 6,322,074

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2021USD ($)ground_lease	Mar. 31, 2020USD ($)
Long-term Purchase Commitment [Line Items]
Commitments for contracts and executed leases, operating and redevelopment and development properties	$ 456.3
Weighted average discount rate, ground leases	5.11%
Weighted average remaining lease term	54 years
Variable lease, cost	$ 0.4	$ 0.9
Environmental matters [Member]
Long-term Purchase Commitment [Line Items]
Accrued environmental remediation liabilities	$ 72.3
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

Commitments and Contingencies_2

Commitments and Contingencies - Minimum Commitment Under Ground Leases (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Minimum commitment under our ground leases
Remaining 2021	$ 4,230
2022	5,642
2023	5,662
2024	5,662
2025	5,662
2026	5,662
Thereafter	275,062
Total undiscounted cash flows	307,582
Present value discount	(209,965)
Ground lease liabilities	$ 97,617	$ 97,778
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	$ 1,000
Average annual percentage rent for previous five years (percent)	50.00%
Previous period included in average annual rent percentage for five-year increases	5 years
Duration of ground lease prior to increase ten years	ten years
Average annual percentage rent for previous ten years (percent)	60.00%
Previous period included in average annual rent percentage for ten-year increases	3 years
Percentage rent increase every five years	5.00%

Fair Value Measurements and D_3

Fair Value Measurements and Disclosures - Assets and Liabilities Reported at Fair Value (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Fair value adjustment of marketable securities and deferred compensation plan liability
Net gain (loss) on marketable securities	$ 1,305	$ (3,226)
Fair value, measurements, recurring [Member] | Fair value (Level 1) [Member]
Assets and Liabilities Reported at Fair Value
Marketable securities	$ 24,089		$ 27,481

Fair Value Measurements and D_4

Fair Value Measurements and Disclosures - Financial Instruments Disclosed at Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Carrying value [Member] | Secured debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of debt, net	$ 252,298	$ 253,582
Carrying value [Member] | Unsecured debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of debt, net	3,671,094	3,670,099
Fair value [Member] | Secured debt [Member] | Fair value (level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of debt, net	272,050	282,559
Fair value [Member] | Unsecured debt [Member] | Fair value (level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of debt, net	$ 3,931,186	$ 4,089,339

Net Income Available to Commo_5

Net Income Available to Common Stockholders Per Share of the Company (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Numerator:
Net income available to common stockholders	$ 497,631	$ 39,817
Allocation to participating securities	(365)	(543)
Numerator for basic and diluted net income available to common stockholders	$ 497,266	$ 39,274
Denominator:
Basic weighted average vested shares outstanding (in shares)	116,344,375	106,875,234
Effect of dilutive securities (in shares)	457,009	514,341
Diluted weighted average vested shares and common stock equivalents outstanding (in shares)	116,801,384	107,389,575
Basic earnings per share:
Net income available to common stockholders per share (in dollars per share)	$ 4.27	$ 0.37
Diluted earnings per share:
Net income available to common stockholders per share (in dollars per share)	$ 4.26	$ 0.37

Net Income Available to Commo_6

Net Income Available to Common Unitholders Per Unit of the Operating Partnership (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Numerator:
Net income available to common unitholders	$ 497,631	$ 39,817
Allocation to participating securities	(365)	(543)
Numerator for basic and diluted net income available to common stockholders	$ 497,266	$ 39,274
Denominator:
Basic weighted average vested shares outstanding (in shares)	116,344,375	106,875,234
Effect of dilutive securities (in shares)	457,009	514,341
Diluted weighted average vested shares and common stock equivalents outstanding (in shares)	116,801,384	107,389,575
Basic earnings per unit:
Net income available to common stockholders per share (in dollars per share)	$ 4.27	$ 0.37
Diluted earnings per unit:
Net income available to common stockholders per share (in dollars per share)	$ 4.26	$ 0.37
Kilroy Realty L.P. [Member]
Numerator:
Net income available to common unitholders	$ 502,517	$ 40,389
Allocation to participating securities	(365)	(543)
Numerator for basic and diluted net income available to common stockholders	$ 502,152	$ 39,846
Denominator:
Basic weighted average vested shares outstanding (in shares)	117,494,949	108,897,027
Effect of dilutive securities (in shares)	457,009	514,341
Diluted weighted average vested shares and common stock equivalents outstanding (in shares)	117,951,958	109,411,368
Basic earnings per unit:
Net income available to common stockholders per share (in dollars per share)	$ 4.27	$ 0.37
Diluted earnings per unit:
Net income available to common stockholders per share (in dollars per share)	$ 4.26	$ 0.36

Supplemental Cash Flow Inform_5

Supplemental Cash Flow Information of the Company - Supplemental Cash Flow (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
SUPPLEMENTAL CASH FLOWS INFORMATION:
Cash paid for interest, net of capitalized interest of $16,131 and $20,403 as of March 31, 2021 and 2020, respectively	$ 12,387	$ 10,035
Capitalized interest	16,131	20,403
Cash paid for amounts included in the measurement of ground lease liabilities	1,455	1,332
NON-CASH INVESTING TRANSACTIONS:
Accrual for expenditures for operating properties and development properties	57,675	129,251
Tenant improvements funded directly by tenants	2,570	2,081
NON-CASH FINANCING TRANSACTIONS:
Accrual of dividends and distributions payable to common stockholders and common unitholders (Note 16)	59,472	57,620
Exchange of common units of the Operating Partnership into shares of the Company’s common stock	$ 0	$ 81

Supplemental Cash Flow Inform_6

Supplemental Cash Flow Information of the Company - Reconciliation of Cash and Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH:
Cash and cash equivalents	$ 657,819	$ 731,991	$ 762,134	$ 60,044
Restricted cash	1,028,759	91,139	16,300	16,300
Cash and cash equivalents and restricted cash	$ 1,686,578	$ 823,130	$ 778,434	$ 76,344

Supplemental Cash Flow Inform_7

Supplemental Cash Flow Information of the Operating Partnership - Supplemental Cash Flow (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
SUPPLEMENTAL CASH FLOWS INFORMATION:
Cash paid for interest, net of capitalized interest of $16,131 and $20,403 as of March 31, 2021 and 2020, respectively	$ 12,387	$ 10,035
Capitalized interest	16,131	20,403
Cash paid for amounts included in the measurement of ground lease liabilities	1,455	1,332
NON-CASH INVESTING TRANSACTIONS:
Accrual for expenditures for operating properties and development properties	57,675	129,251
Tenant improvements funded directly by tenants	2,570	2,081
NON-CASH FINANCING TRANSACTIONS:
Accrual of distributions payable to common unitholders (Note 16)	59,472	57,620
Kilroy Realty L.P. [Member]
SUPPLEMENTAL CASH FLOWS INFORMATION:
Cash paid for interest, net of capitalized interest of $16,131 and $20,403 as of March 31, 2021 and 2020, respectively	12,387	10,035
Capitalized interest	16,131	20,403
Cash paid for amounts included in the measurement of ground lease liabilities	1,455	1,332
NON-CASH INVESTING TRANSACTIONS:
Accrual for expenditures for operating properties and development properties	57,675	129,251
Tenant improvements funded directly by tenants	2,570	2,081
NON-CASH FINANCING TRANSACTIONS:
Accrual of distributions payable to common unitholders (Note 16)	$ 59,472	$ 57,620

Supplemental Cash Flow Inform_8

Supplemental Cash Flow Information of the Operating Partnership - Reconciliation of Cash and Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH:
Cash and cash equivalents	$ 657,819	$ 731,991	$ 762,134	$ 60,044
Restricted cash	1,028,759	91,139	16,300	16,300
Cash and cash equivalents and restricted cash	1,686,578	823,130	778,434	76,344
Kilroy Realty L.P. [Member]
RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH:
Cash and cash equivalents	657,819	731,991	762,134	60,044
Restricted cash	1,028,759	91,139	16,300	16,300
Cash and cash equivalents and restricted cash	$ 1,686,578	$ 823,130	$ 778,434	$ 76,344

Subsequent Events (Details)

Subsequent Events (Details)	Apr. 14, 2021USD ($)	Apr. 29, 2021USD ($)extensionOption	Mar. 31, 2021USD ($)	Dec. 31, 2020USD ($)
Kilroy Realty L.P. [Member] | Revolving credit facility [Member]
Subsequent Event [Line Items]
Maximum borrowing capacity			$ 750,000,000	$ 750,000,000
Subsequent event [Member]
Subsequent Event [Line Items]
Payment of dividends	$ 59,400,000
Subsequent event [Member] | Kilroy Realty L.P. [Member] | Revolving credit facility [Member]
Subsequent Event [Line Items]
Maximum borrowing capacity		$ 1,100,000,000
Number of extension options | extensionOption		2
Extension period		6 months
Interest rate reduction if sustainability performance targets met (percent)		0.01%