Kilroy Realty (KRC) 10-Q 27 Apr 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2018	Apr. 20, 2018
Entity Registrant Name	KILROY REALTY CORP
Entity Central Index Key	1,025,996
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding		98,839,708
Kilroy Realty, L.P. [Member]
Entity Registrant Name	Kilroy Realty, L.P.
Entity Central Index Key	1,493,976
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Amendment Flag	false

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
REAL ESTATE ASSETS (Note 2):
Land and improvements	$ 1,127,100	$ 1,076,172
Buildings and improvements	4,987,617	4,908,797
Undeveloped land and construction in progress	1,530,949	1,432,808
Total real estate assets held for investment	7,645,666	7,417,777
Accumulated depreciation and amortization	(1,312,612)	(1,264,162)
Total real estate assets held for investment, net	6,333,054	6,153,615
CASH AND CASH EQUIVALENTS	53,069	57,649
RESTRICTED CASH	0	9,149
MARKETABLE SECURITIES (Note 11)	21,572	20,674
CURRENT RECEIVABLES, NET (Note 3)	17,602	16,926
DEFERRED RENT RECEIVABLES, NET (Note 3)	251,744	246,391
DEFERRED LEASING COSTS AND ACQUISITION-RELATED INTANGIBLE ASSETS, NET	181,567	183,728
PREPAID EXPENSES AND OTHER ASSETS, NET (Note 4)	107,324	114,706
TOTAL ASSETS	6,965,932	6,802,838
LIABILITIES:
Secured debt, net (Notes 5 and 11)	339,501	340,800
Unsecured debt, net (Notes 5 and 11)	2,155,794	2,006,263
Unsecured line of credit (Notes 5 and 11)	50,000	0
Accounts payable, accrued expenses and other liabilities	223,973	249,637
Accrued dividends and distributions (Note 16)	43,512	43,448
Deferred revenue and acquisition-related intangible liabilities, net	149,563	145,890
Rents received in advance and tenant security deposits	56,117	56,484
Total liabilities	3,018,460	2,842,522
COMMITMENTS AND CONTINGENCIES (Note 10)
Stockholders’ Equity (Note 6):
Common stock, $.01 par value, 150,000,000 shares authorized, 98,839,708 and 98,620,333 shares issued and outstanding, respectively	988	986
Additional paid-in capital	3,816,385	3,822,492
Distributions in excess of earnings	(130,514)	(122,685)
Total stockholders’ equity	3,686,859	3,700,793
Noncontrolling Interests (Notes 1 and 7):
Common units of the Operating Partnership	77,240	77,948
Noncontrolling interests in consolidated property partnerships	183,373	181,575
Total noncontrolling interests	260,613	259,523
Total equity	3,947,472	3,960,316
TOTAL LIABILITIES AND EQUITY (CAPITAL)	$ 6,965,932	$ 6,802,838

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued (in shares)	98,839,708	98,620,333
Common stock, shares outstanding	98,839,708	98,620,333

Consolidated Statements of Oper

Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
REVENUES
Rental income	$ 162,871	$ 156,648
Tenant reimbursements	19,150	19,296
Other property income	801	3,364
Total revenues	182,822	179,308
EXPENSES
Property expenses	31,671	31,241
Real estate taxes	17,146	17,964
Provision for bad debts	(265)	1,298
Ground leases	1,561	1,642
General and administrative expenses	15,559	14,933
Depreciation and amortization	62,715	60,919
Total expenses	128,387	127,997
OTHER (EXPENSES) INCOME
Interest income and other net investment gain/loss (Note 11)	34	1,065
Interest expense (Note 5)	(13,498)	(17,352)
Total other (expenses) income	(13,464)	(16,287)
INCOME FROM OPERATIONS BEFORE GAINS ON SALES OF REAL ESTATE	40,971	35,024
Gains on sales of depreciable operating properties	0	2,257
NET INCOME	40,971	37,281
Net income attributable to noncontrolling common units of the Operating Partnership	(751)	(623)
Net income attributable to noncontrolling interests in consolidated property partnerships	(3,974)	(3,133)
Total income attributable to noncontrolling interests	(4,725)	(3,756)
NET INCOME ATTRIBUTABLE TO KILROY REALTY CORPORATION (KILROY REALTY, L.P.)	36,246	33,525
Preferred dividends	0	(3,351)
Original issuance costs of redeemed preferred stock and preferred units	0	(3,845)
Total preferred dividends	0	(7,196)
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS (UNITHOLDERS)	$ 36,246	$ 26,329
Net income available to common stockholders per share – basic (in dollars per share) (Note 12)	$ 0.36	$ 0.27
Net income available to common stockholders per share – diluted (in dollars per share) (Note 12)	$ 0.36	$ 0.26
Weighted average common shares outstanding – basic (in shares) (Note 12)	98,744,220	97,388,137
Weighted average common shares outstanding – diluted (in shares) (Note 12)	99,213,610	98,018,157
Dividends declared per common share (in dollars per share)	$ 0.425	$ 0.375000

Consolidated Statements of Equi

Consolidated Statements of Equity (Unaudited) - USD ($) $ in Thousands	Total	Preferred Stock [Member]	Common Stock [Member]	Common Stock Additional Paid-in Capital [Member]	Common Stock Distributions in Excess of Earnings [Member]	Total Stockholders' Equity [Member]	Noncontrolling Interests [Member]
Beginning balance at Dec. 31, 2016	$ 3,759,317	$ 192,411	$ 932	$ 3,457,649	$ (107,997)	$ 3,542,995	$ 216,322
Beginning balance (in shares) at Dec. 31, 2016			93,219,439
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	37,281				33,525	33,525	3,756
Redemption of Series G Preferred stock	(100,000)	(96,155)			(3,845)	(100,000)
Issuance of common stock (in shares)			4,427,500
Issuance of common stock	308,849		$ 44	308,805		308,849
Issuance of share-based compensation awards	4,164			4,164		4,164
Non-cash amortization of share-based compensation	6,169			6,169		6,169
Exercise of stock options (in shares)			200,000
Exercise of stock options	8,522		$ 2	8,520		8,522
Settlement of restricted stock units for shares of common stock (in shares)			257,824
Settlement of restricted stock units for shares of common stock	0		$ 3	(3)		0
Repurchase of common stock, stock options and restricted stock units (in shares)			(134,065)
Repurchase of common stock, stock options and restricted stock units	(11,014)		$ (1)	(11,013)		(11,014)
Exchange of common units of the Operating Partnership (in shares)			304,350
Exchange of common units of the Operating Partnership	0		$ 3	10,936		10,939	(10,939)
Contributions from noncontrolling interests in consolidated property partnerships	250					0	250
Distributions to noncontrolling interests in consolidated property partnerships	(4,728)					0	(4,728)
Adjustment for noncontrolling interest	0			(2,936)		(2,936)	2,936
Preferred dividends	(3,351)				(3,351)	(3,351)
Dividends declared per common share and common unit ($.0425 and $0.375 per share/unit for the three months ended March 2018 and 2017, respectively)	(39,318)				(38,539)	(38,539)	(779)
Ending balance at Mar. 31, 2017	3,966,141	$ 96,256	$ 983	3,782,291	(120,207)	3,759,323	206,818
Ending balance (in shares) at Mar. 31, 2017			98,275,048
Beginning balance at Dec. 31, 2017	$ 3,960,316		$ 986	3,822,492	(122,685)	3,700,793	259,523
Beginning balance (in shares) at Dec. 31, 2017	98,620,333		98,620,333
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 40,971				36,246	36,246	4,725
Issuance of share-based compensation awards	1,864			1,864		1,864
Non-cash amortization of share-based compensation	5,094			5,094		5,094
Settlement of restricted stock units for shares of common stock (in shares)			405,067
Settlement of restricted stock units for shares of common stock	0		$ 4	(4)		0
Repurchase of common stock, stock options and restricted stock units (in shares)			(192,195)
Repurchase of common stock, stock options and restricted stock units	(13,642)		$ (2)	(13,640)		(13,642)
Exchange of common units of the Operating Partnership (in shares)			6,503
Exchange of common units of the Operating Partnership	0		$ 0	244		244	(244)
Distributions to noncontrolling interests in consolidated property partnerships	(2,177)					0	(2,177)
Adjustment for noncontrolling interest	0			335		335	(335)
Dividends declared per common share and common unit ($.0425 and $0.375 per share/unit for the three months ended March 2018 and 2017, respectively)	(44,954)				(44,075)	(44,075)	(879)
Ending balance at Mar. 31, 2018	$ 3,947,472		$ 988	$ 3,816,385	$ (130,514)	$ 3,686,859	$ 260,613
Ending balance (in shares) at Mar. 31, 2018	98,839,708		98,839,708

Consolidated Statements of Equ6

Consolidated Statements of Equity (Unaudited) (Parenthetical) - $ / shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Stockholders' Equity [Abstract]
Dividends declared per common share and common unit (in dollars per share)	$ 0.425	$ 0.375000

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 40,971	$ 37,281
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of real estate assets and leasing costs	61,677	59,734
Depreciation of non-real estate furniture, fixtures and equipment	1,038	1,185
(Decrease) increase in provision for bad debts	(265)	1,298
Non-cash amortization of share-based compensation awards	3,598	4,134
Non-cash amortization of deferred financing costs and debt discounts and premiums	315	738
Non-cash amortization of net below market rents	(2,543)	(2,412)
Gain on sale of depreciable operating properties	0	(2,257)
Non-cash amortization of deferred revenue related to tenant-funded tenant improvements	(4,281)	(3,695)
Straight-line rents	(5,359)	(7,611)
Net change in other operating assets	(4,640)	(1,811)
Net change in other operating liabilities	3,598	9,791
Net cash provided by operating activities	94,109	96,375
CASH FLOWS FROM INVESTING ACTIVITIES:
Expenditures for development properties and undeveloped land	(111,424)	(67,957)
Expenditures for acquisition of operating properties (Note 2)	(111,029)	0
Expenditures for operating properties	(35,302)	(21,446)
Net proceeds received from dispositions	0	11,865
Net increase in acquisition-related deposits	(5,000)	(8,850)
Proceeds received from repayment of note receivable (Note 3)	15,100	0
Net cash used in investing activities	(247,655)	(86,388)
CASH FLOWS FROM FINANCING ACTIVITIES:
Borrowings on unsecured revolving credit facility (Note 5)	90,000	0
Repayments on unsecured revolving credit facility (Note 5)	(10,000)	0
Borrowings on unsecured debt (Note 5)	120,000	0
Principal payments on secured debt	(878)	(2,705)
Proceeds from the issuance of unsecured debt	0	250,000
Financing costs	(460)	(1,866)
Net proceeds from issuance of common stock	0	308,849
Redemption of Series G Preferred stock	0	(100,000)
Repurchase of common stock and restricted stock units	(13,642)	(11,014)
Proceeds from exercise of stock options	0	8,522
Distributions to noncontrolling interests in consolidated property partnerships	(2,170)	(4,728)
Contributions from noncontrolling interests in consolidated property partnerships	0	250
Dividends and distributions paid to common stockholders and common unitholders	(43,033)	(217,643)
Dividends and distributions paid to preferred stockholders and preferred unitholders	0	(4,191)
Net cash provided by financing activities	139,817	225,474
Net (decrease) increase in cash and cash equivalents and restricted cash	(13,729)	235,461
Cash and cash equivalents and restricted cash, beginning of period	66,798	250,129
Cash and cash equivalents and restricted cash, end of period	$ 53,069	$ 485,590

Consolidated Balance Sheets (KI

Consolidated Balance Sheets (KILROY REALTY, L.P.) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
REAL ESTATE ASSETS (Note 2):
Land and improvements	$ 1,127,100	$ 1,076,172
Buildings and improvements	4,987,617	4,908,797
Undeveloped land and construction in progress	1,530,949	1,432,808
Total real estate assets held for investment	7,645,666	7,417,777
Accumulated depreciation and amortization	(1,312,612)	(1,264,162)
Total real estate assets held for investment, net	6,333,054	6,153,615
CASH AND CASH EQUIVALENTS	53,069	57,649
RESTRICTED CASH	0	9,149
MARKETABLE SECURITIES (Note 11)	21,572	20,674
CURRENT RECEIVABLES, NET (Note 3)	17,602	16,926
DEFERRED RENT RECEIVABLES, NET (Note 3)	251,744	246,391
DEFERRED LEASING COSTS AND ACQUISITION-RELATED INTANGIBLE ASSETS, NET	181,567	183,728
PREPAID EXPENSES AND OTHER ASSETS, NET (Note 4)	107,324	114,706
TOTAL ASSETS	6,965,932	6,802,838
LIABILITIES:
Secured debt, net (Notes 5 and 11)	339,501	340,800
Unsecured debt, net (Notes 5 and 11)	2,155,794	2,006,263
Unsecured line of credit (Notes 5 and 11)	50,000	0
Accounts payable, accrued expenses and other liabilities	223,973	249,637
Accrued distributions (Note 16)	43,512	43,448
Deferred revenue and acquisition-related intangible liabilities, net	149,563	145,890
Rents received in advance and tenant security deposits	56,117	56,484
Total liabilities	3,018,460	2,842,522
COMMITMENTS AND CONTINGENCIES (Note 10)
CAPITAL:
TOTAL LIABILITIES AND EQUITY (CAPITAL)	6,965,932	6,802,838
Kilroy Realty, L.P. [Member]
REAL ESTATE ASSETS (Note 2):
Land and improvements	1,127,100	1,076,172
Buildings and improvements	4,987,617	4,908,797
Undeveloped land and construction in progress	1,530,949	1,432,808
Total real estate assets held for investment	7,645,666	7,417,777
Accumulated depreciation and amortization	(1,312,612)	(1,264,162)
Total real estate assets held for investment, net	6,333,054	6,153,615
CASH AND CASH EQUIVALENTS	53,069	57,649
RESTRICTED CASH	0	9,149
MARKETABLE SECURITIES (Note 11)	21,572	20,674
CURRENT RECEIVABLES, NET (Note 3)	17,602	16,926
DEFERRED RENT RECEIVABLES, NET (Note 3)	251,744	246,391
DEFERRED LEASING COSTS AND ACQUISITION-RELATED INTANGIBLE ASSETS, NET	181,567	183,728
PREPAID EXPENSES AND OTHER ASSETS, NET (Note 4)	107,324	114,706
TOTAL ASSETS	6,965,932	6,802,838
LIABILITIES:
Secured debt, net (Notes 5 and 11)	339,501	340,800
Unsecured debt, net (Notes 5 and 11)	2,155,794	2,006,263
Unsecured line of credit (Notes 5 and 11)	50,000	0
Accounts payable, accrued expenses and other liabilities	223,973	249,637
Accrued distributions (Note 16)	43,512	43,448
Deferred revenue and acquisition-related intangible liabilities, net	149,563	145,890
Rents received in advance and tenant security deposits	56,117	56,484
Total liabilities	3,018,460	2,842,522
COMMITMENTS AND CONTINGENCIES (Note 10)
CAPITAL:
Common units, 98,839,708 and 98,620,333 held by the general partner and 2,070,690 and 2,077,193 held by common limited partners issued and outstanding, respectively (Note 8)	3,759,196	3,773,941
Noncontrolling interests in consolidated property partnerships and subsidiaries (Note 1)	188,276	186,375
Total capital	3,947,472	3,960,316
TOTAL LIABILITIES AND EQUITY (CAPITAL)	$ 6,965,932	$ 6,802,838

Consolidated Balance Sheets (K9

Consolidated Balance Sheets (KILROY REALTY, L.P.) (Parenthetical) - Common units [Member] - Kilroy Realty, L.P. [Member] - shares	Mar. 31, 2018	Dec. 31, 2017
General partner, units issued	98,839,708	98,620,333
General partners, units outstanding	98,839,708	98,620,333
Limited partners, units issued	2,070,690	2,077,193
Noncontrolling common units of the Operating Partnership	2,070,690	2,077,193

Consolidated Statements of Op10

Consolidated Statements of Operations (KILROY REALTY, L.P.) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
REVENUES
Rental income	$ 162,871	$ 156,648
Tenant reimbursements	19,150	19,296
Other property income	801	3,364
Total revenues	182,822	179,308
EXPENSES
Property expenses	31,671	31,241
Real estate taxes	17,146	17,964
Provision for bad debts	(265)	1,298
Ground leases	1,561	1,642
General and administrative expenses	15,559	14,933
Depreciation and amortization	62,715	60,919
Total expenses	128,387	127,997
OTHER (EXPENSES) INCOME
Interest income and other net investment gain/loss (Note 11)	34	1,065
Interest expense (Note 5)	(13,498)	(17,352)
Total other (expenses) income	(13,464)	(16,287)
INCOME FROM OPERATIONS BEFORE GAINS ON SALES OF REAL ESTATE	40,971	35,024
Gains on sales of depreciable operating properties	0	2,257
NET INCOME	40,971	37,281
Net income attributable to noncontrolling interests in consolidated property partnerships and subsidiaries	(4,725)	(3,756)
NET INCOME ATTRIBUTABLE TO KILROY REALTY CORPORATION (KILROY REALTY, L.P.)	36,246	33,525
Preferred distributions	0	(3,351)
Original issuance costs of redeemed preferred stock and preferred units	0	(3,845)
Total preferred distributions	0	(7,196)
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS (UNITHOLDERS)	$ 36,246	$ 26,329
Net income available to common unitholders per unit-basic (in dollars per unit) (Note 13)	$ 0.36	$ 0.27
Net income available to common unitholders per unit-diluted (in dollars per unit) (Note 13)	$ 0.36	$ 0.26
Weighted average common shares outstanding – basic (in shares) (Note 13)	98,744,220	97,388,137
Weighted average common units outstanding - diluted (in units) (Note 13)	99,213,610	98,018,157
Kilroy Realty, L.P. [Member]
REVENUES
Rental income	$ 162,871	$ 156,648
Tenant reimbursements	19,150	19,296
Other property income	801	3,364
Total revenues	182,822	179,308
EXPENSES
Property expenses	31,671	31,241
Real estate taxes	17,146	17,964
Provision for bad debts	(265)	1,298
Ground leases	1,561	1,642
General and administrative expenses	15,559	14,933
Depreciation and amortization	62,715	60,919
Total expenses	128,387	127,997
OTHER (EXPENSES) INCOME
Interest income and other net investment gain/loss (Note 11)	34	1,065
Interest expense (Note 5)	(13,498)	(17,352)
Total other (expenses) income	(13,464)	(16,287)
INCOME FROM OPERATIONS BEFORE GAINS ON SALES OF REAL ESTATE	40,971	35,024
Gains on sales of depreciable operating properties	0	2,257
NET INCOME	40,971	37,281
Net income attributable to noncontrolling interests in consolidated property partnerships and subsidiaries	(4,078)	(3,227)
NET INCOME ATTRIBUTABLE TO KILROY REALTY CORPORATION (KILROY REALTY, L.P.)	36,893	34,054
Preferred distributions	0	(3,351)
Original issuance costs of redeemed preferred stock and preferred units	0	(3,845)
Total preferred distributions	0	(7,196)
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS (UNITHOLDERS)	$ 36,893	$ 26,858
Net income available to common unitholders per unit-basic (in dollars per unit) (Note 13)	$ 0.36	$ 0.26
Net income available to common unitholders per unit-diluted (in dollars per unit) (Note 13)	$ 0.36	$ 0.26
Weighted average common shares outstanding – basic (in shares) (Note 13)	100,815,477	99,691,684
Weighted average common units outstanding - diluted (in units) (Note 13)	101,284,867	100,321,704
Dividends declared per common unit (in dollars per unit)	$ 0.425	$ 0.375

Consolidated Statements of Capi

Consolidated Statements of Capital (KILROY REALTY, L.P.) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 40,971	$ 37,281
Redemption of Series G Preferred units		(100,000)
Non-cash amortization of share-based compensation	5,094	6,169
Exercise of stock options	0	0
Distributions to noncontrolling interests in consolidated property partnerships	(2,177)	(4,728)
Preferred distributions		(3,351)
Noncontrolling Interests [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	4,725	3,756
Distributions to noncontrolling interests in consolidated property partnerships	(2,177)	(4,728)
Kilroy Realty, L.P. [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	3,960,316	3,759,317
Net income	40,971	37,281
Redemption of Series G Preferred units		(100,000)
Issuance of common units		308,849
Issuance of share-based compensation awards	1,864	4,164
Non-cash amortization of share-based compensation	5,094	6,169
Exercise of stock options		8,522
Exercise of stock options	0	0
Repurchase of common units, stock options and restricted stock units	(13,642)	(11,014)
Contributions from noncontrolling interests in consolidated property partnerships		250
Distributions to noncontrolling interests in consolidated property partnerships	(2,177)	(4,728)
Preferred distributions		(3,351)
Distributions declared per common unit ($0.425 and $0.375 per unit for the three months ended March 2018 and 2017, respectively)	(44,954)	(39,318)
Ending balance	3,947,472	3,966,141
Kilroy Realty, L.P. [Member] | Partners Capital Preferred Units [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		192,411
Redemption of Series G Preferred units		(96,155)
Ending balance		96,256
Kilroy Realty, L.P. [Member] | Partners Capital Common Unit [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	$ 3,773,941	$ 3,431,768
Beginning balance (in units)	100,697,526	95,600,982
Net income	$ 36,893	$ 34,054
Issuance of common units (in units)		4,427,500
Issuance of common units		$ 308,849
Issuance of share-based compensation awards	1,864	4,164
Non-cash amortization of share-based compensation	$ 5,094	$ 6,169
Exercise of stock options (in shares)		200,000
Exercise of stock options		$ 8,522
Settlement of restricted stock units (in units)	405,067	257,824
Exercise of stock options	$ 0	$ 0
Repurchase of common units and restricted stock units (in units)	(192,195)	(134,065)
Repurchase of common units, stock options and restricted stock units	$ (13,642)	$ (11,014)
Contributions from noncontrolling interests in consolidated property partnerships		0
Preferred distributions		(3,351)
Distributions declared per common unit ($0.425 and $0.375 per unit for the three months ended March 2018 and 2017, respectively)	(44,954)	(39,318)
Ending balance	$ 3,759,196	$ 3,735,998
Ending balance (in units)	100,910,398	100,352,241
Kilroy Realty, L.P. [Member] | Total Partners Capital [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		$ 3,624,179
Net income		34,054
Redemption of Series G Preferred units		(100,000)
Issuance of common units		308,849
Issuance of share-based compensation awards		4,164
Non-cash amortization of share-based compensation		6,169
Exercise of stock options		8,522
Exercise of stock options		0
Repurchase of common units, stock options and restricted stock units		(11,014)
Contributions from noncontrolling interests in consolidated property partnerships		0
Preferred distributions		(3,351)
Distributions declared per common unit ($0.425 and $0.375 per unit for the three months ended March 2018 and 2017, respectively)		(39,318)
Ending balance		3,832,254
Kilroy Realty, L.P. [Member] | Noncontrolling Interests [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	$ 186,375	135,138
Net income	4,078	3,227
Contributions from noncontrolling interests in consolidated property partnerships		250
Distributions to noncontrolling interests in consolidated property partnerships	(2,177)	(4,728)
Ending balance	$ 188,276	$ 133,887

Consolidated Statements of Ca12

Consolidated Statements of Capital (KILROY REALTY, L.P.) (Parenthetical) - $ / shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Kilroy Realty, L.P. [Member]
Dividends declared per common unit (in dollars per unit)	$ 0.425	$ 0.375

Consolidated Statements of Ca13

Consolidated Statements of Cash Flows (KILROY REALTY, L.P.) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 40,971	$ 37,281
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of real estate assets and leasing costs	61,677	59,734
Depreciation of non-real estate furniture, fixtures and equipment	1,038	1,185
(Decrease) increase in provision for bad debts	(265)	1,298
Non-cash amortization of share-based compensation awards	3,598	4,134
Non-cash amortization of deferred financing costs and debt discounts and premiums	315	738
Non-cash amortization of net below market rents	(2,543)	(2,412)
Gain on sale of depreciable operating properties	0	(2,257)
Non-cash amortization of deferred revenue related to tenant-funded tenant improvements	(4,281)	(3,695)
Straight-line rents	(5,359)	(7,611)
Net change in other operating assets	(4,640)	(1,811)
Net change in other operating liabilities	3,598	9,791
Net cash provided by operating activities	94,109	96,375
CASH FLOWS FROM INVESTING ACTIVITIES:
Expenditures for development properties and undeveloped land	(111,424)	(67,957)
Expenditures for acquisition of operating properties (Note 2)	(111,029)	0
Expenditures for operating properties	(35,302)	(21,446)
Net proceeds received from dispositions	0	11,865
Net increase in acquisition-related deposits	(5,000)	(8,850)
Proceeds received from repayment of note receivable (Note 3)	15,100	0
Net cash used in investing activities	(247,655)	(86,388)
CASH FLOWS FROM FINANCING ACTIVITIES:
Borrowings on unsecured revolving credit facility (Note 5)	90,000	0
Repayments on unsecured revolving credit facility (Note 5)	(10,000)	0
Borrowings on unsecured debt (Note 5)	120,000	0
Principal payments on secured debt	(878)	(2,705)
Proceeds from the issuance of unsecured debt	0	250,000
Financing costs	(460)	(1,866)
Net proceeds from issuance of common units	0	308,849
Redemption of Series G Preferred units	0	(100,000)
Repurchase of common units and restricted stock units	(13,642)	(11,014)
Proceeds from exercise of stock options	0	8,522
Distributions to noncontrolling interests in consolidated property partnerships	(2,170)	(4,728)
Contributions from noncontrolling interests in consolidated property partnerships	0	250
Distributions paid to common unitholders	(43,033)	(217,643)
Distributions paid to preferred unitholders	0	(4,191)
Net cash provided by financing activities	139,817	225,474
Net (decrease) increase in cash and cash equivalents and restricted cash	(13,729)	235,461
Cash and cash equivalents and restricted cash, beginning of period	66,798	250,129
Cash and cash equivalents and restricted cash, end of period	53,069	485,590
Kilroy Realty, L.P. [Member]
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	40,971	37,281
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of real estate assets and leasing costs	61,677	59,734
Depreciation of non-real estate furniture, fixtures and equipment	1,038	1,185
(Decrease) increase in provision for bad debts	(265)	1,298
Non-cash amortization of share-based compensation awards	3,598	4,134
Non-cash amortization of deferred financing costs and debt discounts and premiums	315	738
Non-cash amortization of net below market rents	(2,543)	(2,412)
Gain on sale of depreciable operating properties	0	(2,257)
Non-cash amortization of deferred revenue related to tenant-funded tenant improvements	(4,281)	(3,695)
Straight-line rents	(5,359)	(7,611)
Net change in other operating assets	(4,640)	(1,811)
Net change in other operating liabilities	3,598	9,791
Net cash provided by operating activities	94,109	96,375
CASH FLOWS FROM INVESTING ACTIVITIES:
Expenditures for development properties and undeveloped land	(111,424)	(67,957)
Expenditures for acquisition of operating properties (Note 2)	(111,029)	0
Expenditures for operating properties	(35,302)	(21,446)
Net proceeds received from dispositions	0	11,865
Net increase in acquisition-related deposits	(5,000)	(8,850)
Proceeds received from repayment of note receivable (Note 3)	15,100	0
Net cash used in investing activities	(247,655)	(86,388)
CASH FLOWS FROM FINANCING ACTIVITIES:
Borrowings on unsecured revolving credit facility (Note 5)	90,000	0
Repayments on unsecured revolving credit facility (Note 5)	(10,000)	0
Borrowings on unsecured debt (Note 5)	120,000	0
Principal payments on secured debt	(878)	(2,705)
Proceeds from the issuance of unsecured debt	0	250,000
Financing costs	(460)	(1,866)
Net proceeds from issuance of common units	0	308,849
Redemption of Series G Preferred units	0	(100,000)
Repurchase of common units and restricted stock units	(13,642)	(11,014)
Proceeds from exercise of stock options	0	8,522
Distributions to noncontrolling interests in consolidated property partnerships	(2,170)	(4,728)
Contributions from noncontrolling interests in consolidated property partnerships	0	250
Distributions paid to common unitholders	(43,033)	(217,643)
Distributions paid to preferred unitholders	0	(4,191)
Net cash provided by financing activities	139,817	225,474
Net (decrease) increase in cash and cash equivalents and restricted cash	(13,729)	235,461
Cash and cash equivalents and restricted cash, beginning of period	66,798	250,129
Cash and cash equivalents and restricted cash, end of period	$ 53,069	$ 485,590

Organization, Ownership and Bas

Organization, Ownership and Basis of Presentation	3 Months Ended
	Mar. 31, 2018
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, Orange County, 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”) and Kilroy Realty Finance Partnership, L.P. (the “Finance 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, 2018 : Number of Buildings Rentable Square Feet (unaudited) Number of Tenants Percentage Occupied (unaudited) Percentage Leased (unaudited) Stabilized Office Properties 104 13,866,127 515 94.3 % 96.7 % Number of Number of Units 2018 Average Occupancy (unaudited) Stabilized Residential Property 1 200 83.0 % Our stabilized portfolio includes all of our properties with the exception of development and redevelopment properties currently under construction or committed for construction, “lease-up” properties, real estate assets held for sale and undeveloped land. 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 “lease-up” properties as office and retail properties we recently developed or redeveloped that have not yet reached 95% occupancy and are within one year following cessation of major construction activities. There were no operating properties in “lease-up” or held for sale as of March 31, 2018 . As of March 31, 2018 , the following properties were excluded from our stabilized portfolio. We did not have any redevelopment properties at March 31, 2018 . Number of Properties/Projects Estimated Rentable Square Feet (1) Development projects under construction (2) 5 2,106,000 ________________________ (1) Estimated rentable square feet upon completion. (2) Includes 86,000 square feet of Production, Distribution, and Repair (“PDR”) space. In addition to the estimated office rentable square feet noted above, development projects under construction also include 120,000 square feet of retail space and 237 residential units. Our stabilized portfolio also excludes our future development pipeline, which as of March 31, 2018 was comprised of six potential development sites, representing approximately 46 gross acres of undeveloped land. As of March 31, 2018 , 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 twelve office properties and one development project under construction 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 and an office project held by a consolidated variable interest entity for future transactions intended to qualify as like-kind exchanges pursuant to Section 1031 of the Code (“Section 1031 Exchanges”). Two of the three 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, 2018 , the Company owned a 56% common equity interest in both 100 First LLC and 303 Second LLC. The third property partnership, Redwood City Partners, LLC (“Redwood LLC”) owned two office properties in Redwood City, California. As of March 31, 2018 , 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, the Finance Partnership, Kilroy Services, LLC (“KSLLC”), 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, the Finance Partnership, KSLLC, 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, 2018 , the Company owned an approximate 97.9% common general partnership interest in the Operating Partnership. The remaining approximate 2.1% common limited partnership interest in the Operating Partnership as of March 31, 2018 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.” Kilroy Realty Finance, Inc., which is a wholly-owned subsidiary of the Company, is the sole general partner of the Finance Partnership and owns a 1.0% common general partnership interest in the Finance Partnership. The Operating Partnership owns the remaining 99.0% common limited partnership interest. 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, 2018 . 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, 2017 . Variable Interest Entities The Operating Partnership is a variable interest entity (“VIE”) of the Company 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, 2018 , the consolidated financial statements of the Company included three VIEs in addition to the Operating Partnership: 100 First LLC, 303 Second LLC, and an entity established during the first quarter of 2018 to facilitate potential future Section 1031 Exchanges. At March 31, 2018 , the Company and the Operating Partnership were determined to be the primary beneficiaries of these three VIEs since we had the ability to control the activities that most significantly impact each of the VIE’s economic performance. As of March 31, 2018 , the three VIEs’ total assets, liabilities and noncontrolling interests included on our consolidated balance sheet were approximately $543.5 million (of which $489.4 million related to real estate held for investment), approximately $31.5 million and approximately $177.2 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, 2017 , the consolidated financial statements of the Company and the Operating Partnership included two VIEs in which we were deemed to be the primary beneficiary: 100 First LLC and 303 Second LLC. At December 31, 2017 , the impact of consolidating the VIEs increased the Company’s total assets, liabilities and noncontrolling interests on our consolidated balance sheet by approximately $426.5 million (of which $382.1 million related to real estate held for investment), approximately $27.3 million and approximately $175.4 million , respectively. Accounting Pronouncements Adopted January 1, 2018 Effective January 1, 2018, we adopted Financial Accounting Standards Board (“FASB”) ASU No. 2014-09 “Revenue From Contracts with Customers (Topic 606)” (“ASU 2014-09”) and the related FASB ASU Nos. 2016-12 and 2016-20, which provide practical expedients, technical corrections, and improvements for certain aspects of ASU 2014-09, on a modified retrospective basis. ASU 2014-09 establishes a single comprehensive model for entities to use in accounting for revenue from contracts with customers and supersedes most of the existing revenue recognition guidance. We evaluated each of the Company’s revenue streams to determine the sources of revenue that are impacted by ASU 2014-09 and concluded that two revenue streams, sales of real estate and revenue from our multi-tenant parking arrangements, fall within the scope of Topic 606. We evaluated the impact of the adoption of the guidance on the timing of gain recognition for our historical dispositions and concluded there was no impact to our consolidated financial statements given the simplicity and straight forward nature of our historical disposition transactions. We also evaluated the impact of the guidance on the timing and pattern of revenue recognition for our multi-tenant parking arrangements and determined there was no impact to our consolidated financial statements. We generally provide parking for our multi-tenant properties based on the prevailing market rate per parking space, which adjusts based on prevailing market rates during the tenant’s occupancy, and we recognize parking revenue as parking spaces are utilized by the tenant. Given the structure of these arrangements whereby the amount of parking revenue we recognize corresponds directly to the tenant’s use, we were able to apply the practical expedient provided in Accounting Standards Codification (“ASC”) 606-10-50-14(b) (the “right to invoice” practical expedient). As a result of applying this practical expedient, we are not required to disclose the transaction price allocated to future performance obligations for multi-tenant parking since we cannot predict or estimate the use of such parking spaces. During the three months ended March 31, 2018 and 2017 , we recognized $6.6 million and $6.7 million , respectively, of parking revenue for arrangements that are within the scope of Topic 606, which is included in rental revenues on our consolidated statements of operations. We concluded that the adoption of Topic 606 did not have an impact on our consolidated financial statements or a material impact on the notes to our consolidated financial statements. Effective January 1, 2018, we adopted FASB ASU No. 2017-09 “Compensation - Stock Compensation (Topic 718)” on a prospective basis. Under the guidance, an entity will not apply modification accounting to a share-based payment award if the award’s fair value, vesting conditions, and classification as an equity or liability instrument remain the same immediately before and after the change. The adoption of this guidance did not have an impact on our consolidated financial statements or notes to our consolidated financial statements. Effective January 1, 2018, we adopted FASB ASU No. 2017-05 “Other Income - Gains and Losses from the Derecognition of Nonfinancial Assets (Subtopic 610-20)” (“ASU 2017-05”) on a retrospective basis. This standard clarifies the scope of the original guidance within Subtopic 610-20 “Gains and Losses from the Derecognition of Nonfinancial Assets” that was issued in connection with ASU 2014-09 which provided guidance for recognizing gains and losses from the transfer of nonfinancial assets in transactions with noncustomers. Additionally, ASU 2017-05 adds guidance pertaining to the partial sales of real estate and clarifies that nonfinancial assets within the scope of ASC 610-20 may include nonfinancial assets transferred within a legal entity to a counterparty. For example, a parent may transfer control of nonfinancial assets by transferring ownership interests in a consolidated subsidiary. We evaluated the impact of the new amendments on our historical transactions and concluded that there was no impact. As such, the adoption of this guidance did not have an impact on our consolidated financial statements or notes to our consolidated financial statements. Effective January 1, 2018, we adopted FASB ASU No. 2016-15 (“ASU 2016-15”) which provides guidance where there is diversity in practice in how certain cash receipts and cash payments are presented and classified in the statement of cash flows, on a retrospective basis. The adoption of this guidance did not have an impact on our consolidated financial statements or notes to our consolidated financial statements. Effective January 1, 2018, we adopted FASB ASU No. 2016-01 (“ASU 2016-01”) which amends the accounting guidance on the classification and measurement of financial instruments and FASB ASU No. 2018-03 (“ASU 2018-03”) which provides technical corrections and improvements to ASU 2016-01, on a modified retrospective basis. The amendments require that all investments in equity securities, including other ownership interests, are reported at fair value with changes in fair value reported in net income. This requirement does not apply to investments that qualify for equity method accounting or to those that result in consolidation of the investee or for which the entity has elected the predictability exception to fair value measurement. Additionally, the amendments require that the portion of the total fair value change caused by a change in instrument-specific credit risk for financial liabilities for which the fair value option has been elected would be recognized in other comprehensive income. Any accumulated amount remaining in other comprehensive income is reclassified to earnings when the liability is extinguished. The adoption of this guidance did not have an impact on our consolidated financial statements or notes to our consolidated financial statements since our only financial instruments within the scope of ASU 2016-01 and 2018-03 are the marketable securities related to our deferred compensation plan which are classified as trading securities and marked to market at fair value through earnings each reporting period. Accounting Pronouncements Effective January 1, 2019 ASU No. 2016-02 “Leases (Topic 842)” On February 25, 2016, the FASB issued ASU No. 2016-02 “Leases (Topic 842)” (“ASU 2016-02”) to amend the accounting guidance for leases. The accounting applied by a lessor is largely unchanged under ASU 2016-02. However, the standard requires lessees to recognize lease assets and lease liabilities for leases classified as operating leases on the balance sheet. Lessees will recognize in the statement of financial position a liability to make lease payments and a right-of-use asset representing its right to use the underlying asset for the lease term. For leases with a term of 12 months or less, a lessee is permitted to make an accounting policy election by class of underlying asset not to recognize lease assets and lease liabilities. If a lessee makes this election, it will recognize lease expense for such leases generally on a straight-line basis over the lease term. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018. Early adoption is permitted. We continue to have an active project team, led by senior accounting management, that is proactively working to analyze and evaluate the impact of the guidance on our consolidated financial statements. In January 2018, the FASB released an exposure draft to amend ASU No. 2016-02 that would (1) simplify transition requirements for both lessees and lessors by adding an option that would permit an organization to apply the transition provisions of the new standard at its adoption date instead of at the earliest comparative period presented in its financial statements and (2) provide a practical expedient for lessors that would permit lessors to make an accounting policy election to not separate nonlease components from the associated lease components if certain criteria are met. In March 2018, the FASB decided to finalize the changes with respect to optional transition relief and approved a practical expedient for lessors that would permit lessors to make an accounting policy election to not separate nonlease components from the associated lease components, by class of underlying asset, if the following two criteria are met: (1) the timing and pattern of transfer of the lease and nonlease components are the same and (2) the lease component would be classified as an operating lease if accounted for separately. For leases where we are the lessor, we currently believe that we will elect the optional transition relief and that we will meet the noted criteria to not be required to bifurcate and separately report nonlease components, such as common area maintenance revenue, for operating leases on our consolidated statements of operations. As a result, we currently believe that leases where we are the lessor will be accounted for in a similar method to existing standards with the underlying leased asset being reported and recognized as a real estate asset. The FASB is expected to issue an Accounting Standards Update codifying these changes in the coming months. We currently expect to adopt ASU 2016-02 using the practical expedients proposed in the standard and the changes approved by the FASB. ASU 2016-02 also specifies that upon adoption, lessors will no longer be able to capitalize and amortize certain leasing related costs and instead will only be permitted to capitalize and amortize incremental direct leasing costs. As a result, we have concluded that upon the adoption of the standard, we will be required to expense as incurred certain leasing costs we are currently able to capitalize and amortize as deferred leasing costs under existing guidance. We are currently in the process of analyzing the impact of this change in the guidance and we currently believe this change will have a material impact to the Company’s consolidated financial statements and results of operations upon adoption of the standard. For leases where we are the lessee, specifically for our ground leases, we currently believe that the adoption of the standard will significantly change the accounting on our consolidated balance sheets since both existing ground leases and any future ground leases will be required to be recorded on the Company’s consolidated balance sheets as an obligation of the Company. We currently believe that existing ground leases executed before the January 1, 2019 adoption date will continue to be accounted for as operating leases and the new guidance will not have a material impact on our recognition of ground lease expense or our results of operations. However, we believe that we will be required to recognize a right of use asset and a lease liability on our consolidated balance sheets equal to the present value of the minimum lease payments required in accordance with each ground lease. As of March 31, 2018 , our future undiscounted minimum rental payments under these leases totaled $250.2 million , with several of the leases containing provisions for rental payments to fluctuate based on fair market value and operating income measurements with expirations through 2093. In addition, we currently believe that for new ground leases entered into after the adoption date of the new standard, such leases could be required to be accounted for as financing type leases, resulting in ground lease expense recorded using the effective interest method instead of on a straight-line basis over the term of the lease. This could have a significant impact on our results of operations if we enter into material new ground leases after the date of adoption since ground lease expense calculated using the effective interest method results in an increased amount of ground lease expense in the earlier years of a ground lease as compared to the current straight-line method. Accounting Pronouncements Effective in 2020 and Beyond ASU No. 2016-13 “Financial Instruments - Credit Losses (Topic 326)” On June 16, 2016, the FASB issued ASU No. 2016-13 (“ASU 2016-13”) to amend the accounting for credit losses for certain financial instruments. Under the new guidance, an entity recognizes its estimate of expected credit losses as an allowance, which the FASB believes will result in more timely recognition of such losses. ASU 2016-13 is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Early adoption is permitted for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. The Company does not currently anticipate that the guidance will have a material impact on our consolidated financial statements or notes to our consolidated financial statements.

Acquisitions

Acquisitions	3 Months Ended
	Mar. 31, 2018
Asset Acquisitions [Abstract]
Acquisitions	Acquisitions Operating Property Acquisitions During the three months ended March 31, 2018 , we acquired the three operating properties listed below from an unrelated third party. The acquisition was funded with proceeds from the Company’s unsecured revolving credit facility and unsecured term loan facility. Property Date of Acquisition Number of Buildings Rentable Square Feet (unaudited) Purchase Price (in millions) (1) 345, 347 & 349 Oyster Point Boulevard, South San Francisco, CA January 31, 2018 3 145,530 $ 111.0 ________________________ (1) Excludes acquisition-related costs. The related assets, liabilities and results of operations of the acquired property are included in the consolidated financial statements as of the date of acquisition. The following table summarizes the assets acquired and liabilities assumed as of the date of acquisition, excluding acquisition-related costs: Total 2018 Operating Property Acquisitions Assets Land and improvements $ 50,928 Buildings and improvements (1) 59,123 Deferred leasing costs and acquisition-related intangible assets (2) 4,470 Total assets acquired 114,521 Liabilities Deferred revenue and acquisition-related intangible liabilities (3) 3,521 Total liabilities assumed 3,521 Net assets and liabilities acquired $ 111,000 ________________________ (1) Represents buildings, building improvements and tenant improvements. (2) Represents in-place leases (approximately $3.8 million with a weighted average amortization period of 2.6 years) and leasing commissions (approximately $0.7 million with a weighted average amortization period of 3.5 years). (3) Represents below-market leases (approximately $3.5 million with a weighted average amortization period of 9.8 years).

Receivables

Receivables	3 Months Ended
	Mar. 31, 2018
Receivables [Abstract]
Receivables	Receivables Current Receivables, net Current receivables, net consisted of the following as of March 31, 2018 and December 31, 2017 : March 31, 2018 December 31, 2017 (in thousands) Current receivables $ 19,630 $ 19,235 Allowance for uncollectible tenant receivables (2,028 ) (2,309 ) Current receivables, net $ 17,602 $ 16,926 Deferred Rent Receivables, net Deferred rent receivables, net consisted of the following as of March 31, 2018 and December 31, 2017 : March 31, 2018 December 31, 2017 (in thousands) Deferred rent receivables $ 254,969 $ 249,629 Allowance for deferred rent receivables (3,225 ) (3,238 ) Deferred rent receivables, net $ 251,744 $ 246,391

Prepaid Expenses and Other Asse

Prepaid Expenses and Other Assets, Net	3 Months Ended
	Mar. 31, 2018
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, 2018 and December 31, 2017 : March 31, 2018 December 31, 2017 (in thousands) Furniture, fixtures and other long-lived assets, net $ 38,541 $ 39,686 Note receivable (1) 4,867 19,912 Prepaid expenses & acquisition deposits 63,916 55,108 Total prepaid expenses and other assets, net $ 107,324 $ 114,706 ________________________ (1) During the three months ended March 31, 2018 , a note receivable with a balance of $15.1 million was repaid to the Company.

Secured and Unsecured Debt of t

Secured and Unsecured Debt of the Operating Partnership	3 Months Ended
	Mar. 31, 2018
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, the unsecured term loan facility and all of the unsecured senior notes. Unsecured Revolving Credit Facility and Term Loan Facility The following table summarizes the balance and terms of our unsecured revolving credit facility as of March 31, 2018 and December 31, 2017 : March 31, 2018 December 31, 2017 (in thousands) Outstanding borrowings $ 50,000 $ — Remaining borrowing capacity 700,000 750,000 Total borrowing capacity (1) $ 750,000 $ 750,000 Interest rate (2) 2.72 % 2.56 % Facility fee-annual rate (3) 0.200% Maturity date July 2022 ________________________ (1) We may elect to borrow, subject to bank approval and obtaining commitments for any additional borrowing capacity, up to an additional $600.0 million under an accordion feature under the terms of the unsecured revolving credit facility and unsecured term loan facility. (2) Our unsecured revolving credit facility interest rate was calculated based on an annual rate of LIBOR plus 1.000% as of March 31, 2018 and December 31, 2017 . (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, 2018 and December 31, 2017 , $5.7 million and $6.0 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. During the three months ended March 31, 2018 , we borrowed the full $150.0 million borrowing capacity of our unsecured term loan facility. In connection with the funding of the outstanding borrowings, we transferred $30.0 million of outstanding borrowings under the unsecured revolving credit facility to the balance of our unsecured term loan facility. As a result, only $120.0 million of cash proceeds were received from the funding of the unsecured term loan facility. The following table summarizes the balance and terms of our unsecured term loan facility as of March 31, 2018 and December 31, 2017 : March 31, 2018 December 31, 2017 (in thousands) Outstanding borrowings $ 150,000 $ — Remaining borrowing capacity — 150,000 Total borrowing capacity (1)(2) $ 150,000 $ 150,000 Interest rate (3) 2.90 % 2.66 % Undrawn facility fee-annual rate (4) 0.200% Maturity date July 2022 ________________________ (1) In July 2017, the Facility was amended to include a 12-month delayed draw option on the unsecured term loan facility. The Company may repay amounts under the unsecured term loan facility through July 2018, however, no additional draws may be made. (2) As of March 31, 2018 and December 31, 2017 , $1.1 million and $1.2 million of unamortized deferred financing costs, respectively, remained to be amortized through the maturity date of our unsecured term loan facility. (3) Our unsecured term loan facility interest rate was calculated based on an annual rate of LIBOR plus 1.100% as of March 31, 2018 and December 31, 2017 . (4) Prior to borrowing the full capacity of our unsecured term loan facility, the undrawn facility fee was calculated based on any unused borrowing capacity and was paid on a quarterly basis. Debt Covenants and Restrictions The unsecured revolving credit facility, unsecured term loan facility, unsecured senior notes, 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, 2018 . Debt Maturities The following table summarizes the stated debt maturities and scheduled amortization payments of our issued and outstanding debt, excluding unamortized debt discounts, premiums and deferred financing costs, as of March 31, 2018 : Year (in thousands) Remaining 2018 $ 2,706 2019 76,309 2020 255,137 2021 5,342 2022 205,554 Thereafter 2,018,469 Total (1) $ 2,563,517 ________________________ (1) Includes gross principal balance of outstanding debt before the effect of the following at March 31, 2018 : $14.3 million of unamortized deferred financing costs for the unsecured term loan facility, unsecured senior notes and secured debt, $6.1 million of unamortized discounts for the unsecured senior notes and $2.1 million of unamortized premiums for the secured debt. 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, 2018 and 2017 . 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, 2018 2017 (in thousands) Gross interest expense $ 27,080 $ 27,515 Capitalized interest and deferred financing costs (13,582 ) (10,163 ) Interest expense $ 13,498 $ 17,352

Stockholders' Equity of the Com

Stockholders' Equity of the Company	3 Months Ended
	Mar. 31, 2018
Equity [Abstract]
Stockholders' Equity of the Company	Stockholders’ Equity of the Company At-The-Market Stock Offering Program Under our current at-the-market stock offering program, which commenced in December 2014, we may offer and sell shares of our common stock having an aggregate gross sales price of up to $300.0 million from time to time in “at-the-market” offerings. No shares of common stock were sold under this program during the three months ended March 31, 2018 . Since commencement of the program through March 31, 2018 , we have sold 2,694,242 shares of common stock having an aggregate gross sales price of $200.1 million . As of March 31, 2018 , shares of common stock having an aggregate gross sales price of up to $99.9 million remain available to be sold under this program. Actual future sales will depend upon a variety of factors, including but not limited to market conditions, the trading price of the Company’s common stock and our capital needs. We have no obligation to sell the remaining shares available for sale under this program.

Noncontrolling Interests on the

Noncontrolling Interests on the Company's Consolidated Financial Statements	3 Months Ended
	Mar. 31, 2018
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 97.9% common general partnership interest in the Operating Partnership as of March 31, 2018 , December 31, 2017 and March 31, 2017 , respectively. The remaining approximate 2.1% common limited partnership interest as of March 31, 2018 , December 31, 2017 and March 31, 2017 , respectively, was owned by non-affiliated investors and certain of our executive officers and directors in the form of noncontrolling common units. There were 2,070,690 , 2,077,193 and 2,077,193 common units outstanding held by these investors, executive officers and directors as of March 31, 2018 , December 31, 2017 and March 31, 2017 , 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 $146.1 million and $154.5 million as of March 31, 2018 and December 31, 2017 , respectively. This redemption value does not necessarily represent the amount that would be distributed with respect to each noncontrolling common unit in the event of our termination or liquidation. In the event of our termination or liquidation, it is expected in most cases that each common unit would be entitled to a liquidating distribution equal to the liquidating distribution payable in respect of each share of the Company’s common stock.

Partners' Capital of the Operat

Partners' Capital of the Operating Partnership	3 Months Ended
	Mar. 31, 2018
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, 2018 December 31, 2017 March 31, 2017 Company owned common units in the Operating Partnership 98,839,708 98,620,333 98,275,048 Company owned general partnership interest 97.9 % 97.9 % 97.9 % Noncontrolling common units of the Operating Partnership 2,070,690 2,077,193 2,077,193 Ownership interest of noncontrolling interest 2.1 % 2.1 % 2.1 % For further discussion of the noncontrolling common units as of March 31, 2018 and December 31, 2017 , refer to Note 7.

Share-Based Compensation

Share-Based Compensation	3 Months Ended
	Mar. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation	Share-Based Compensation Stockholder Approved Equity Compensation Plans As of March 31, 2018 , we maintained one share-based incentive compensation plan, the Kilroy Realty 2006 Incentive Award Plan, as amended (the “2006 Plan”). As of March 31, 2018 , approximately 1.8 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 target levels for the performance or market conditions (as defined below) for awards still in a performance period. 2018 Share-Based Compensation Grants In January and February 2018 , the Executive Compensation Committee of the Company’s Board of Directors awarded 282,038 restricted stock units (“RSUs”) to certain officers of the Company under the 2006 Plan, which included 158,205 RSUs (at the target level of performance) that are subject to market and/or performance-based vesting requirements (the “2018 Performance-Based RSUs”) and 123,833 RSUs that are subject to time-based vesting requirements (the “2018 Time-Based RSUs”). 2018 Performance-Based RSU Grant The 2018 Performance-Based RSUs are scheduled to vest at the end of a three -year period (consisting of calendar years 2018-2020). A target number of 2018 Performance-Based RSUs were awarded, and the final number of 2018 Performance-Based RSUs that vest (which may be more or less than the target number) will be based upon (1) the achievement of pre-set FFO per share goals for the year ending December 31, 2018 that applies to 100% of the Performance-Based RSUs awarded (the “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 2018 Performance-Based RSUs are also subject to a three -year service vesting provision 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 2018 Performance-Based RSUs ultimately earned could fluctuate from the target number of 2018 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 2018 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. As of March 31, 2018 , the number of 2018 Performance-Based RSUs estimated to be earned based on the Company’s estimate of the performance conditions measured against the applicable goals was 158,205 , and the compensation cost recorded to date for this program was based on that estimate. Compensation expense for the 2018 Performance-Based RSU grant will be recorded on a straight-line basis over the three -year period. Each 2018 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 2018 Performance-Based RSU grants covered by the debt to EBITDA ratio performance condition was based on the $66.46 share price on the grant date. The determination of the grant date fair value of the portion of the 2018 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 a $70.08 grant date fair value per share. Fair Value Assumptions Expected share price volatility 20.00% Risk-free interest rate 2.37% Expected life 2.9 years The computation of expected volatility is based on a blend of the historical volatility of our shares of common stock over approximately 5.8 years, as that is expected to be most consistent with future volatility and equates to a time period twice as long as 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 14, 2018 . The expected life of the 2018 Performance-Based RSUs is equal to the remaining 2.9 -year vesting period as of February 14, 2018 . The total grant date fair value of the 2018 Performance-Based RSU awards was $10.8 million on the February 14, 2018 grant date of the awards. For the three months ended March 31, 2018 , 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 as discussed above. 2018 Time-Based RSU Grant The 2018 Time-Based RSUs are scheduled to vest in three equal annual installments beginning on January 5, 2019 through January 5, 2021. Compensation expense for the 2018 Time-Based RSUs will be recognized on a straight-line basis over the three -year service vesting period. Each 2018 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 2018 Time-Based RSU awards was $8.4 million , which was based on the $70.37 and $66.46 closing share prices of the Company’s common stock on the NYSE on the January 29, 2018 and February 14, 2018 , respectively, grant dates of the awards. Share-Based Compensation Cost Recorded During the Period The total compensation cost for all share-based compensation programs was $5.1 million and $6.2 million for the three months ended March 31, 2018 and 2017 , respectively. Of the total share-based compensation costs, $1.5 million and $2.0 million was capitalized as part of real estate assets and deferred leasing costs for the three months ended March 31, 2018 and 2017 , respectively. As of March 31, 2018 , there was approximately $41.3 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 2.2 years. The remaining compensation cost related to these nonvested incentive awards had been recognized in periods prior to March 31, 2018 .

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies General As of March 31, 2018 , we had commitments of approximately $748.4 million , excluding our ground lease commitments, for contracts and executed leases directly related to our operating properties and development projects. Environmental Matters We follow the policy of monitoring all of our properties, both acquisition 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, 2018 , we had accrued environmental remediation liabilities of approximately $28.2 million recorded on our consolidated balance sheets in connection with certain of our in-process and future development projects. It is possible that we could incur additional environmental remediation costs in connection with these future development projects. However, given we are in the pre-development phase on these future development projects, potential additional environmental costs 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, 2018
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, 2018 and December 31, 2017 : Fair Value (Level 1) (1) March 31, 2018 December 31, 2017 Description (in thousands) Marketable securities (2) $ 21,572 $ 20,674 ________________________ (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 for the period. The following table sets forth the net (loss) gain on marketable securities recorded during the three months ended March 31, 2018 and 2017 : Three Months Ended March 31, 2018 2017 Description (in thousands) Net (loss) gain on marketable securities $ (404 ) $ 671 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, 2018 and December 31, 2017 : March 31, 2018 December 31, 2017 Carrying Fair (1) Carrying Fair (1) (in thousands) Liabilities Secured debt, net $ 339,501 $ 339,618 $ 340,800 $ 346,858 Unsecured debt, net 2,155,794 2,162,552 2,006,263 2,077,199 Unsecured line of credit 50,000 50,058 — — ________________________ (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, 2018
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, 2018 and 2017 : Three Months Ended March 31, 2018 2017 (in thousands, except share and per share amounts) Numerator: Net income attributable to Kilroy Realty Corporation $ 36,246 $ 33,525 Total preferred dividends — (7,196 ) Allocation to participating securities (1) (471 ) (448 ) Numerator for basic and diluted net income available to common stockholders $ 35,775 $ 25,881 Denominator: Basic weighted average vested shares outstanding 98,744,220 97,388,137 Effect of dilutive securities 469,390 630,020 Diluted weighted average vested shares and common share equivalents outstanding 99,213,610 98,018,157 Basic earnings per share: Net income available to common stockholders per share $ 0.36 $ 0.27 Diluted earnings per share: Net income available to common stockholders per share $ 0.36 $ 0.26 ________________________ (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, 2018 and 2017 . Certain market measure-based RSUs are not included in dilutive securities for the three months ended March 31, 2018 and 2017 , as not all performance metrics had been met by the end of the applicable reporting periods. See Note 9 “Share-Based Compensation” for additional information regarding share-based compensation.

Net Income Available to Commo26

Net Income Available to Common Unitholders Per Unit of the Operating Partnership	3 Months Ended
	Mar. 31, 2018
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, 2018 and 2017 : Three Months Ended March 31, 2018 2017 (in thousands, except share and per share amounts) Numerator: Net income attributable to Kilroy Realty Corporation $ 36,246 $ 33,525 Total preferred dividends — (7,196 ) Allocation to participating securities (1) (471 ) (448 ) Numerator for basic and diluted net income available to common stockholders $ 35,775 $ 25,881 Denominator: Basic weighted average vested shares outstanding 98,744,220 97,388,137 Effect of dilutive securities 469,390 630,020 Diluted weighted average vested shares and common share equivalents outstanding 99,213,610 98,018,157 Basic earnings per share: Net income available to common stockholders per share $ 0.36 $ 0.27 Diluted earnings per share: Net income available to common stockholders per share $ 0.36 $ 0.26 ________________________ (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, 2018 and 2017 . Certain market measure-based RSUs are not included in dilutive securities for the three months ended March 31, 2018 and 2017 , as not all performance metrics had been met by the end of the applicable reporting periods. See Note 9 “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, 2018 and 2017 : Three Months Ended March 31, 2018 2017 (in thousands, except unit and per unit amounts) Numerator: Net income attributable to Kilroy Realty, L.P. $ 36,893 $ 34,054 Total preferred distributions — (7,196 ) Allocation to participating securities (1) (471 ) (448 ) Numerator for basic and diluted net income available to common unitholders $ 36,422 $ 26,410 Denominator: Basic weighted average vested units outstanding 100,815,477 99,691,684 Effect of dilutive securities 469,390 630,020 Diluted weighted average vested units and common unit equivalents outstanding 101,284,867 100,321,704 Basic earnings per unit: Net income available to common unitholders per unit $ 0.36 $ 0.26 Diluted earnings per unit: Net income available to common unitholders per unit $ 0.36 $ 0.26 ________________________ (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, 2018 and 2017 . Certain market measure-based RSUs are not included in dilutive securities for the three months ended March 31, 2018 and 2017 , as not all performance metrics had been met by the end of the applicable reporting periods. See Note 9 “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, 2018
Supplemental Cash Flow Elements [Abstract]
Supplemental Cash Flow Information of the Company	Supplemental Cash Flow Information of the Company Supplemental cash flow information is included as follows (in thousands): Three Months Ended March 31, 2018 2017 SUPPLEMENTAL CASH FLOWS INFORMATION: Cash paid for interest, net of capitalized interest of $13,051 and $9,829 as of March 31, 2018 and 2017, respectively $ 9,699 $ 18,206 NON-CASH INVESTING TRANSACTIONS: Accrual for expenditures for operating properties and development properties $ 57,155 $ 50,056 Tenant improvements funded directly by tenants $ 2,014 $ 7,416 NON-CASH FINANCING TRANSACTIONS: Accrual of dividends and distributions payable to common stockholders and common unitholders $ 43,512 $ 38,176 Accrual of dividends and distributions payable to preferred stockholders and preferred unitholders $ — $ 797 Exchange of common units of the Operating Partnership into shares of the Company’s common stock $ 244 $ 10,939 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, 2018 and 2017 . Three Months Ended March 31, 2018 2017 RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH: Cash and cash equivalents at beginning of period $ 57,649 $ 193,418 Restricted cash at beginning of period 9,149 56,711 Cash and cash equivalents and restricted cash at beginning of period $ 66,798 $ 250,129 Cash and cash equivalents at end of period $ 53,069 $ 478,391 Restricted cash at end of period — 7,199 Cash and cash equivalents and restricted cash at end of period $ 53,069 $ 485,590

Supplemental Cash Flow Inform28

Supplemental Cash Flow Information of the Operating Partnership	3 Months Ended
	Mar. 31, 2018
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 is included as follows (in thousands): Three Months Ended March 31, 2018 2017 SUPPLEMENTAL CASH FLOWS INFORMATION: Cash paid for interest, net of capitalized interest of $13,051 and $9,829 as of March 31, 2018 and 2017, respectively $ 9,699 $ 18,206 NON-CASH INVESTING TRANSACTIONS: Accrual for expenditures for operating properties and development properties $ 57,155 $ 50,056 Tenant improvements funded directly by tenants $ 2,014 $ 7,416 NON-CASH FINANCING TRANSACTIONS: Accrual of dividends and distributions payable to common stockholders and common unitholders $ 43,512 $ 38,176 Accrual of dividends and distributions payable to preferred stockholders and preferred unitholders $ — $ 797 Exchange of common units of the Operating Partnership into shares of the Company’s common stock $ 244 $ 10,939 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, 2018 and 2017 . Three Months Ended March 31, 2018 2017 RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH: Cash and cash equivalents at beginning of period $ 57,649 $ 193,418 Restricted cash at beginning of period 9,149 56,711 Cash and cash equivalents and restricted cash at beginning of period $ 66,798 $ 250,129 Cash and cash equivalents at end of period $ 53,069 $ 478,391 Restricted cash at end of period — 7,199 Cash and cash equivalents and restricted cash at end of period $ 53,069 $ 485,590
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 is included as follows (in thousands): Three Months Ended March 31, 2018 2017 SUPPLEMENTAL CASH FLOWS INFORMATION: Cash paid for interest, net of capitalized interest of $13,051 and $9,829 as of March 31, 2018 and 2017, respectively $ 9,699 $ 18,206 NON-CASH INVESTING TRANSACTIONS: Accrual for expenditures for operating properties and development properties $ 57,155 $ 50,056 Tenant improvements funded directly by tenants $ 2,014 $ 7,416 NON-CASH FINANCING TRANSACTIONS: Accrual of distributions payable to common unitholders $ 43,512 $ 38,176 Accrual of distributions payable to preferred unitholders $ — $ 797 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, 2018 and 2017 . Three Months Ended March 31, 2018 2017 RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH: Cash and cash equivalents at beginning of period $ 57,649 $ 193,418 Restricted cash at beginning of period 9,149 56,711 Cash and cash equivalents and restricted cash at beginning of period $ 66,798 $ 250,129 Cash and cash equivalents at end of period $ 53,069 $ 478,391 Restricted cash at end of period — 7,199 Cash and cash equivalents and restricted cash at end of period $ 53,069 $ 485,590

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2018
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On April 18, 2018 , aggregate dividends, distributions and dividend equivalents of $43.5 million were paid to common stockholders, common unitholders and RSU holders of record on March 29, 2018 .

Organization, Ownership and B30

Organization, Ownership and Basis of Presentation (Policies)	3 Months Ended
	Mar. 31, 2018
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, the Finance Partnership, Kilroy Services, LLC (“KSLLC”), 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, the Finance Partnership, KSLLC, 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, 2018 . 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, 2017 .
New accounting pronouncements	Accounting Pronouncements Adopted January 1, 2018 Effective January 1, 2018, we adopted Financial Accounting Standards Board (“FASB”) ASU No. 2014-09 “Revenue From Contracts with Customers (Topic 606)” (“ASU 2014-09”) and the related FASB ASU Nos. 2016-12 and 2016-20, which provide practical expedients, technical corrections, and improvements for certain aspects of ASU 2014-09, on a modified retrospective basis. ASU 2014-09 establishes a single comprehensive model for entities to use in accounting for revenue from contracts with customers and supersedes most of the existing revenue recognition guidance. We evaluated each of the Company’s revenue streams to determine the sources of revenue that are impacted by ASU 2014-09 and concluded that two revenue streams, sales of real estate and revenue from our multi-tenant parking arrangements, fall within the scope of Topic 606. We evaluated the impact of the adoption of the guidance on the timing of gain recognition for our historical dispositions and concluded there was no impact to our consolidated financial statements given the simplicity and straight forward nature of our historical disposition transactions. We also evaluated the impact of the guidance on the timing and pattern of revenue recognition for our multi-tenant parking arrangements and determined there was no impact to our consolidated financial statements. We generally provide parking for our multi-tenant properties based on the prevailing market rate per parking space, which adjusts based on prevailing market rates during the tenant’s occupancy, and we recognize parking revenue as parking spaces are utilized by the tenant. Given the structure of these arrangements whereby the amount of parking revenue we recognize corresponds directly to the tenant’s use, we were able to apply the practical expedient provided in Accounting Standards Codification (“ASC”) 606-10-50-14(b) (the “right to invoice” practical expedient). As a result of applying this practical expedient, we are not required to disclose the transaction price allocated to future performance obligations for multi-tenant parking since we cannot predict or estimate the use of such parking spaces. During the three months ended March 31, 2018 and 2017 , we recognized $6.6 million and $6.7 million , respectively, of parking revenue for arrangements that are within the scope of Topic 606, which is included in rental revenues on our consolidated statements of operations. We concluded that the adoption of Topic 606 did not have an impact on our consolidated financial statements or a material impact on the notes to our consolidated financial statements. Effective January 1, 2018, we adopted FASB ASU No. 2017-09 “Compensation - Stock Compensation (Topic 718)” on a prospective basis. Under the guidance, an entity will not apply modification accounting to a share-based payment award if the award’s fair value, vesting conditions, and classification as an equity or liability instrument remain the same immediately before and after the change. The adoption of this guidance did not have an impact on our consolidated financial statements or notes to our consolidated financial statements. Effective January 1, 2018, we adopted FASB ASU No. 2017-05 “Other Income - Gains and Losses from the Derecognition of Nonfinancial Assets (Subtopic 610-20)” (“ASU 2017-05”) on a retrospective basis. This standard clarifies the scope of the original guidance within Subtopic 610-20 “Gains and Losses from the Derecognition of Nonfinancial Assets” that was issued in connection with ASU 2014-09 which provided guidance for recognizing gains and losses from the transfer of nonfinancial assets in transactions with noncustomers. Additionally, ASU 2017-05 adds guidance pertaining to the partial sales of real estate and clarifies that nonfinancial assets within the scope of ASC 610-20 may include nonfinancial assets transferred within a legal entity to a counterparty. For example, a parent may transfer control of nonfinancial assets by transferring ownership interests in a consolidated subsidiary. We evaluated the impact of the new amendments on our historical transactions and concluded that there was no impact. As such, the adoption of this guidance did not have an impact on our consolidated financial statements or notes to our consolidated financial statements. Effective January 1, 2018, we adopted FASB ASU No. 2016-15 (“ASU 2016-15”) which provides guidance where there is diversity in practice in how certain cash receipts and cash payments are presented and classified in the statement of cash flows, on a retrospective basis. The adoption of this guidance did not have an impact on our consolidated financial statements or notes to our consolidated financial statements. Effective January 1, 2018, we adopted FASB ASU No. 2016-01 (“ASU 2016-01”) which amends the accounting guidance on the classification and measurement of financial instruments and FASB ASU No. 2018-03 (“ASU 2018-03”) which provides technical corrections and improvements to ASU 2016-01, on a modified retrospective basis. The amendments require that all investments in equity securities, including other ownership interests, are reported at fair value with changes in fair value reported in net income. This requirement does not apply to investments that qualify for equity method accounting or to those that result in consolidation of the investee or for which the entity has elected the predictability exception to fair value measurement. Additionally, the amendments require that the portion of the total fair value change caused by a change in instrument-specific credit risk for financial liabilities for which the fair value option has been elected would be recognized in other comprehensive income. Any accumulated amount remaining in other comprehensive income is reclassified to earnings when the liability is extinguished. The adoption of this guidance did not have an impact on our consolidated financial statements or notes to our consolidated financial statements since our only financial instruments within the scope of ASU 2016-01 and 2018-03 are the marketable securities related to our deferred compensation plan which are classified as trading securities and marked to market at fair value through earnings each reporting period. Accounting Pronouncements Effective January 1, 2019 ASU No. 2016-02 “Leases (Topic 842)” On February 25, 2016, the FASB issued ASU No. 2016-02 “Leases (Topic 842)” (“ASU 2016-02”) to amend the accounting guidance for leases. The accounting applied by a lessor is largely unchanged under ASU 2016-02. However, the standard requires lessees to recognize lease assets and lease liabilities for leases classified as operating leases on the balance sheet. Lessees will recognize in the statement of financial position a liability to make lease payments and a right-of-use asset representing its right to use the underlying asset for the lease term. For leases with a term of 12 months or less, a lessee is permitted to make an accounting policy election by class of underlying asset not to recognize lease assets and lease liabilities. If a lessee makes this election, it will recognize lease expense for such leases generally on a straight-line basis over the lease term. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018. Early adoption is permitted. We continue to have an active project team, led by senior accounting management, that is proactively working to analyze and evaluate the impact of the guidance on our consolidated financial statements. In January 2018, the FASB released an exposure draft to amend ASU No. 2016-02 that would (1) simplify transition requirements for both lessees and lessors by adding an option that would permit an organization to apply the transition provisions of the new standard at its adoption date instead of at the earliest comparative period presented in its financial statements and (2) provide a practical expedient for lessors that would permit lessors to make an accounting policy election to not separate nonlease components from the associated lease components if certain criteria are met. In March 2018, the FASB decided to finalize the changes with respect to optional transition relief and approved a practical expedient for lessors that would permit lessors to make an accounting policy election to not separate nonlease components from the associated lease components, by class of underlying asset, if the following two criteria are met: (1) the timing and pattern of transfer of the lease and nonlease components are the same and (2) the lease component would be classified as an operating lease if accounted for separately. For leases where we are the lessor, we currently believe that we will elect the optional transition relief and that we will meet the noted criteria to not be required to bifurcate and separately report nonlease components, such as common area maintenance revenue, for operating leases on our consolidated statements of operations. As a result, we currently believe that leases where we are the lessor will be accounted for in a similar method to existing standards with the underlying leased asset being reported and recognized as a real estate asset. The FASB is expected to issue an Accounting Standards Update codifying these changes in the coming months. We currently expect to adopt ASU 2016-02 using the practical expedients proposed in the standard and the changes approved by the FASB. ASU 2016-02 also specifies that upon adoption, lessors will no longer be able to capitalize and amortize certain leasing related costs and instead will only be permitted to capitalize and amortize incremental direct leasing costs. As a result, we have concluded that upon the adoption of the standard, we will be required to expense as incurred certain leasing costs we are currently able to capitalize and amortize as deferred leasing costs under existing guidance. We are currently in the process of analyzing the impact of this change in the guidance and we currently believe this change will have a material impact to the Company’s consolidated financial statements and results of operations upon adoption of the standard. For leases where we are the lessee, specifically for our ground leases, we currently believe that the adoption of the standard will significantly change the accounting on our consolidated balance sheets since both existing ground leases and any future ground leases will be required to be recorded on the Company’s consolidated balance sheets as an obligation of the Company. We currently believe that existing ground leases executed before the January 1, 2019 adoption date will continue to be accounted for as operating leases and the new guidance will not have a material impact on our recognition of ground lease expense or our results of operations. However, we believe that we will be required to recognize a right of use asset and a lease liability on our consolidated balance sheets equal to the present value of the minimum lease payments required in accordance with each ground lease. As of March 31, 2018 , our future undiscounted minimum rental payments under these leases totaled $250.2 million , with several of the leases containing provisions for rental payments to fluctuate based on fair market value and operating income measurements with expirations through 2093. In addition, we currently believe that for new ground leases entered into after the adoption date of the new standard, such leases could be required to be accounted for as financing type leases, resulting in ground lease expense recorded using the effective interest method instead of on a straight-line basis over the term of the lease. This could have a significant impact on our results of operations if we enter into material new ground leases after the date of adoption since ground lease expense calculated using the effective interest method results in an increased amount of ground lease expense in the earlier years of a ground lease as compared to the current straight-line method. Accounting Pronouncements Effective in 2020 and Beyond ASU No. 2016-13 “Financial Instruments - Credit Losses (Topic 326)” On June 16, 2016, the FASB issued ASU No. 2016-13 (“ASU 2016-13”) to amend the accounting for credit losses for certain financial instruments. Under the new guidance, an entity recognizes its estimate of expected credit losses as an allowance, which the FASB believes will result in more timely recognition of such losses. ASU 2016-13 is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Early adoption is permitted for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. The Company does not currently anticipate that the guidance will have a material impact on our consolidated financial statements or notes to our consolidated financial statements.
Revenue	Effective January 1, 2018, we adopted Financial Accounting Standards Board (“FASB”) ASU No. 2014-09 “Revenue From Contracts with Customers (Topic 606)” (“ASU 2014-09”) and the related FASB ASU Nos. 2016-12 and 2016-20, which provide practical expedients, technical corrections, and improvements for certain aspects of ASU 2014-09, on a modified retrospective basis. ASU 2014-09 establishes a single comprehensive model for entities to use in accounting for revenue from contracts with customers and supersedes most of the existing revenue recognition guidance. We evaluated each of the Company’s revenue streams to determine the sources of revenue that are impacted by ASU 2014-09 and concluded that two revenue streams, sales of real estate and revenue from our multi-tenant parking arrangements, fall within the scope of Topic 606. We evaluated the impact of the adoption of the guidance on the timing of gain recognition for our historical dispositions and concluded there was no impact to our consolidated financial statements given the simplicity and straight forward nature of our historical disposition transactions. We also evaluated the impact of the guidance on the timing and pattern of revenue recognition for our multi-tenant parking arrangements and determined there was no impact to our consolidated financial statements. We generally provide parking for our multi-tenant properties based on the prevailing market rate per parking space, which adjusts based on prevailing market rates during the tenant’s occupancy, and we recognize parking revenue as parking spaces are utilized by the tenant. Given the structure of these arrangements whereby the amount of parking revenue we recognize corresponds directly to the tenant’s use, we were able to apply the practical expedient provided in Accounting Standards Codification (“ASC”) 606-10-50-14(b) (the “right to invoice” practical expedient). As a result of applying this practical expedient, we are not required to disclose the transaction price allocated to future performance obligations for multi-tenant parking since we cannot predict or estimate the use of such parking spaces. During the three months ended March 31, 2018 and 2017 , we recognized $6.6 million and $6.7 million , respectively, of parking revenue for arrangements that are within the scope of Topic 606, which is included in rental revenues on our consolidated statements of operations. We concluded that the adoption of Topic 606 did not have an impact on our consolidated financial statements or a material impact on the notes to our consolidated financial statements.

Organization, Ownership and B31

Organization, Ownership and Basis of Presentation (Tables)	3 Months Ended
	Mar. 31, 2018
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, 2018 : Number of Buildings Rentable Square Feet (unaudited) Number of Tenants Percentage Occupied (unaudited) Percentage Leased (unaudited) Stabilized Office Properties 104 13,866,127 515 94.3 % 96.7 % Number of Number of Units 2018 Average Occupancy (unaudited) Stabilized Residential Property 1 200 83.0 % As of March 31, 2018 , the following properties were excluded from our stabilized portfolio. We did not have any redevelopment properties at March 31, 2018 . Number of Properties/Projects Estimated Rentable Square Feet (1) Development projects under construction (2) 5 2,106,000 ________________________ (1) Estimated rentable square feet upon completion. (2) Includes 86,000 square feet of Production, Distribution, and Repair (“PDR”) space. In addition to the estimated office rentable square feet noted above, development projects under construction also include 120,000 square feet of retail space and 237 residential units.

Acquisitions (Tables)

Acquisitions (Tables)	3 Months Ended
	Mar. 31, 2018
Asset Acquisitions [Abstract]
Schedule of acquisitions	During the three months ended March 31, 2018 , we acquired the three operating properties listed below from an unrelated third party. The acquisition was funded with proceeds from the Company’s unsecured revolving credit facility and unsecured term loan facility. Property Date of Acquisition Number of Buildings Rentable Square Feet (unaudited) Purchase Price (in millions) (1) 345, 347 & 349 Oyster Point Boulevard, South San Francisco, CA January 31, 2018 3 145,530 $ 111.0 ________________________ (1) Excludes acquisition-related costs.
Schedule of estimated fair values of the assets acquired and liabilities assumed	The following table summarizes the assets acquired and liabilities assumed as of the date of acquisition, excluding acquisition-related costs: Total 2018 Operating Property Acquisitions Assets Land and improvements $ 50,928 Buildings and improvements (1) 59,123 Deferred leasing costs and acquisition-related intangible assets (2) 4,470 Total assets acquired 114,521 Liabilities Deferred revenue and acquisition-related intangible liabilities (3) 3,521 Total liabilities assumed 3,521 Net assets and liabilities acquired $ 111,000 ________________________ (1) Represents buildings, building improvements and tenant improvements. (2) Represents in-place leases (approximately $3.8 million with a weighted average amortization period of 2.6 years) and leasing commissions (approximately $0.7 million with a weighted average amortization period of 3.5 years). (3) Represents below-market leases (approximately $3.5 million with a weighted average amortization period of 9.8 years).

Receivables (Tables)

Receivables (Tables)	3 Months Ended
	Mar. 31, 2018
Receivables [Abstract]
Current receivables, net	Current receivables, net consisted of the following as of March 31, 2018 and December 31, 2017 : March 31, 2018 December 31, 2017 (in thousands) Current receivables $ 19,630 $ 19,235 Allowance for uncollectible tenant receivables (2,028 ) (2,309 ) Current receivables, net $ 17,602 $ 16,926
Deferred rent receivables, net	Deferred rent receivables, net consisted of the following as of March 31, 2018 and December 31, 2017 : March 31, 2018 December 31, 2017 (in thousands) Deferred rent receivables $ 254,969 $ 249,629 Allowance for deferred rent receivables (3,225 ) (3,238 ) Deferred rent receivables, net $ 251,744 $ 246,391

Prepaid Expenses and Other As34

Prepaid Expenses and Other Assets, Net (Tables)	3 Months Ended
	Mar. 31, 2018
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, 2018 and December 31, 2017 : March 31, 2018 December 31, 2017 (in thousands) Furniture, fixtures and other long-lived assets, net $ 38,541 $ 39,686 Note receivable (1) 4,867 19,912 Prepaid expenses & acquisition deposits 63,916 55,108 Total prepaid expenses and other assets, net $ 107,324 $ 114,706 ________________________ (1) During the three months ended March 31, 2018 , a note receivable with a balance of $15.1 million was repaid to the Company.

Secured and Unsecured Debt of35

Secured and Unsecured Debt of the Operating Partnership (Tables) - Kilroy Realty, L.P. [Member]	3 Months Ended
	Mar. 31, 2018
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, 2018 and December 31, 2017 : March 31, 2018 December 31, 2017 (in thousands) Outstanding borrowings $ 50,000 $ — Remaining borrowing capacity 700,000 750,000 Total borrowing capacity (1) $ 750,000 $ 750,000 Interest rate (2) 2.72 % 2.56 % Facility fee-annual rate (3) 0.200% Maturity date July 2022 ________________________ (1) We may elect to borrow, subject to bank approval and obtaining commitments for any additional borrowing capacity, up to an additional $600.0 million under an accordion feature under the terms of the unsecured revolving credit facility and unsecured term loan facility. (2) Our unsecured revolving credit facility interest rate was calculated based on an annual rate of LIBOR plus 1.000% as of March 31, 2018 and December 31, 2017 . (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, 2018 and December 31, 2017 , $5.7 million and $6.0 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 following table summarizes the balance and terms of our unsecured term loan facility as of March 31, 2018 and December 31, 2017 : March 31, 2018 December 31, 2017 (in thousands) Outstanding borrowings $ 150,000 $ — Remaining borrowing capacity — 150,000 Total borrowing capacity (1)(2) $ 150,000 $ 150,000 Interest rate (3) 2.90 % 2.66 % Undrawn facility fee-annual rate (4) 0.200% Maturity date July 2022 ________________________ (1) In July 2017, the Facility was amended to include a 12-month delayed draw option on the unsecured term loan facility. The Company may repay amounts under the unsecured term loan facility through July 2018, however, no additional draws may be made. (2) As of March 31, 2018 and December 31, 2017 , $1.1 million and $1.2 million of unamortized deferred financing costs, respectively, remained to be amortized through the maturity date of our unsecured term loan facility. (3) Our unsecured term loan facility interest rate was calculated based on an annual rate of LIBOR plus 1.100% as of March 31, 2018 and December 31, 2017 . (4) Prior to borrowing the full capacity of our unsecured term loan facility, the undrawn facility fee was calculated based on any unused borrowing capacity and was paid on a quarterly basis.
Schedule of debt maturities	The following table summarizes the stated debt maturities and scheduled amortization payments of our issued and outstanding debt, excluding unamortized debt discounts, premiums and deferred financing costs, as of March 31, 2018 : Year (in thousands) Remaining 2018 $ 2,706 2019 76,309 2020 255,137 2021 5,342 2022 205,554 Thereafter 2,018,469 Total (1) $ 2,563,517 ________________________ (1) Includes gross principal balance of outstanding debt before the effect of the following at March 31, 2018 : $14.3 million of unamortized deferred financing costs for the unsecured term loan facility, unsecured senior notes and secured debt, $6.1 million of unamortized discounts for the unsecured senior notes and $2.1 million of unamortized premiums for the secured debt.
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, 2018 and 2017 . 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, 2018 2017 (in thousands) Gross interest expense $ 27,080 $ 27,515 Capitalized interest and deferred financing costs (13,582 ) (10,163 ) Interest expense $ 13,498 $ 17,352

Partners' Capital of the Oper36

Partners' Capital of the Operating Partnership (Tables)	3 Months Ended
	Mar. 31, 2018
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, 2018 December 31, 2017 March 31, 2017 Company owned common units in the Operating Partnership 98,839,708 98,620,333 98,275,048 Company owned general partnership interest 97.9 % 97.9 % 97.9 % Noncontrolling common units of the Operating Partnership 2,070,690 2,077,193 2,077,193 Ownership interest of noncontrolling interest 2.1 % 2.1 % 2.1 %

Share-Based Compensation (Table

Share-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of share-based payment award, restricted stock units, valuation assumptions	Fair Value Assumptions Expected share price volatility 20.00% Risk-free interest rate 2.37% Expected life 2.9 years

Fair Value Measurements and D38

Fair Value Measurements and Disclosures (Tables)	3 Months Ended
	Mar. 31, 2018
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, 2018 and December 31, 2017 : Fair Value (Level 1) (1) March 31, 2018 December 31, 2017 Description (in thousands) Marketable securities (2) $ 21,572 $ 20,674 ________________________ (1) Based on quoted prices in active markets for identical securities. (2) The marketable securities are held in a limited rabbi trust.
Fair value adjustment of marketable securities and deferred compensation plan liability	The following table sets forth the net (loss) gain on marketable securities recorded during the three months ended March 31, 2018 and 2017 : Three Months Ended March 31, 2018 2017 Description (in thousands) Net (loss) gain on marketable securities $ (404 ) $ 671
Carrying value and fair value of company's remaining financial assets and liabilities	The following table sets forth the carrying value and the fair value of our other financial instruments as of March 31, 2018 and December 31, 2017 : March 31, 2018 December 31, 2017 Carrying Fair (1) Carrying Fair (1) (in thousands) Liabilities Secured debt, net $ 339,501 $ 339,618 $ 340,800 $ 346,858 Unsecured debt, net 2,155,794 2,162,552 2,006,263 2,077,199 Unsecured line of credit 50,000 50,058 — — ________________________ (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 Commo39

Net Income Available to Common Stockholders Per Share of the Company (Tables)	3 Months Ended
	Mar. 31, 2018
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, 2018 and 2017 : Three Months Ended March 31, 2018 2017 (in thousands, except share and per share amounts) Numerator: Net income attributable to Kilroy Realty Corporation $ 36,246 $ 33,525 Total preferred dividends — (7,196 ) Allocation to participating securities (1) (471 ) (448 ) Numerator for basic and diluted net income available to common stockholders $ 35,775 $ 25,881 Denominator: Basic weighted average vested shares outstanding 98,744,220 97,388,137 Effect of dilutive securities 469,390 630,020 Diluted weighted average vested shares and common share equivalents outstanding 99,213,610 98,018,157 Basic earnings per share: Net income available to common stockholders per share $ 0.36 $ 0.27 Diluted earnings per share: Net income available to common stockholders per share $ 0.36 $ 0.26 ________________________ (1) Participating securities include nonvested shares, certain time-based RSUs and vested market measure-based RSUs.

Net Income Available to Commo40

Net Income Available to Common Unitholders Per Unit of the Operating Partnership (Tables)	3 Months Ended
	Mar. 31, 2018
Net Income Available To Common Unitholders [Line Items]
Net income (loss) available to common unitholders	The following table reconciles the numerator and denominator in computing the Company’s basic and diluted per-share computations for net income available to common stockholders for the three months ended March 31, 2018 and 2017 : Three Months Ended March 31, 2018 2017 (in thousands, except share and per share amounts) Numerator: Net income attributable to Kilroy Realty Corporation $ 36,246 $ 33,525 Total preferred dividends — (7,196 ) Allocation to participating securities (1) (471 ) (448 ) Numerator for basic and diluted net income available to common stockholders $ 35,775 $ 25,881 Denominator: Basic weighted average vested shares outstanding 98,744,220 97,388,137 Effect of dilutive securities 469,390 630,020 Diluted weighted average vested shares and common share equivalents outstanding 99,213,610 98,018,157 Basic earnings per share: Net income available to common stockholders per share $ 0.36 $ 0.27 Diluted earnings per share: Net income available to common stockholders per share $ 0.36 $ 0.26 ________________________ (1) Participating securities include nonvested shares, certain time-based RSUs and vested market measure-based RSUs.
Kilroy Realty, L.P. [Member]
Net Income Available To Common Unitholders [Line Items]
Net income (loss) available to common unitholders	The following table reconciles the numerator and denominator in computing the Operating Partnership’s basic and diluted per-unit computations for net income available to common unitholders for the three months ended March 31, 2018 and 2017 : Three Months Ended March 31, 2018 2017 (in thousands, except unit and per unit amounts) Numerator: Net income attributable to Kilroy Realty, L.P. $ 36,893 $ 34,054 Total preferred distributions — (7,196 ) Allocation to participating securities (1) (471 ) (448 ) Numerator for basic and diluted net income available to common unitholders $ 36,422 $ 26,410 Denominator: Basic weighted average vested units outstanding 100,815,477 99,691,684 Effect of dilutive securities 469,390 630,020 Diluted weighted average vested units and common unit equivalents outstanding 101,284,867 100,321,704 Basic earnings per unit: Net income available to common unitholders per unit $ 0.36 $ 0.26 Diluted earnings per unit: Net income available to common unitholders per unit $ 0.36 $ 0.26 ________________________ (1) Participating securities include nonvested shares, certain time-based RSUs and vested market measure-based RSUs.

Supplemental Cash Flow Inform41

Supplemental Cash Flow Information of the Company (Tables)	3 Months Ended
	Mar. 31, 2018
Supplemental Cash Flow Elements [Abstract]
Schedule of supplemental cash flows	Supplemental cash flow information is included as follows (in thousands): Three Months Ended March 31, 2018 2017 SUPPLEMENTAL CASH FLOWS INFORMATION: Cash paid for interest, net of capitalized interest of $13,051 and $9,829 as of March 31, 2018 and 2017, respectively $ 9,699 $ 18,206 NON-CASH INVESTING TRANSACTIONS: Accrual for expenditures for operating properties and development properties $ 57,155 $ 50,056 Tenant improvements funded directly by tenants $ 2,014 $ 7,416 NON-CASH FINANCING TRANSACTIONS: Accrual of dividends and distributions payable to common stockholders and common unitholders $ 43,512 $ 38,176 Accrual of dividends and distributions payable to preferred stockholders and preferred unitholders $ — $ 797 Exchange of common units of the Operating Partnership into shares of the Company’s common stock $ 244 $ 10,939
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, 2018 and 2017 . Three Months Ended March 31, 2018 2017 RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH: Cash and cash equivalents at beginning of period $ 57,649 $ 193,418 Restricted cash at beginning of period 9,149 56,711 Cash and cash equivalents and restricted cash at beginning of period $ 66,798 $ 250,129 Cash and cash equivalents at end of period $ 53,069 $ 478,391 Restricted cash at end of period — 7,199 Cash and cash equivalents and restricted cash at end of period $ 53,069 $ 485,590
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, 2018 and 2017 . Three Months Ended March 31, 2018 2017 RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH: Cash and cash equivalents at beginning of period $ 57,649 $ 193,418 Restricted cash at beginning of period 9,149 56,711 Cash and cash equivalents and restricted cash at beginning of period $ 66,798 $ 250,129 Cash and cash equivalents at end of period $ 53,069 $ 478,391 Restricted cash at end of period — 7,199 Cash and cash equivalents and restricted cash at end of period $ 53,069 $ 485,590

Supplemental Cash Flow Inform42

Supplemental Cash Flow Information of the Operating Partnership (Tables)	3 Months Ended
	Mar. 31, 2018
Other Significant Noncash Transactions [Line Items]
Schedule of supplemental cash flows	Supplemental cash flow information is included as follows (in thousands): Three Months Ended March 31, 2018 2017 SUPPLEMENTAL CASH FLOWS INFORMATION: Cash paid for interest, net of capitalized interest of $13,051 and $9,829 as of March 31, 2018 and 2017, respectively $ 9,699 $ 18,206 NON-CASH INVESTING TRANSACTIONS: Accrual for expenditures for operating properties and development properties $ 57,155 $ 50,056 Tenant improvements funded directly by tenants $ 2,014 $ 7,416 NON-CASH FINANCING TRANSACTIONS: Accrual of dividends and distributions payable to common stockholders and common unitholders $ 43,512 $ 38,176 Accrual of dividends and distributions payable to preferred stockholders and preferred unitholders $ — $ 797 Exchange of common units of the Operating Partnership into shares of the Company’s common stock $ 244 $ 10,939
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, 2018 and 2017 . Three Months Ended March 31, 2018 2017 RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH: Cash and cash equivalents at beginning of period $ 57,649 $ 193,418 Restricted cash at beginning of period 9,149 56,711 Cash and cash equivalents and restricted cash at beginning of period $ 66,798 $ 250,129 Cash and cash equivalents at end of period $ 53,069 $ 478,391 Restricted cash at end of period — 7,199 Cash and cash equivalents and restricted cash at end of period $ 53,069 $ 485,590
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, 2018 and 2017 . Three Months Ended March 31, 2018 2017 RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH: Cash and cash equivalents at beginning of period $ 57,649 $ 193,418 Restricted cash at beginning of period 9,149 56,711 Cash and cash equivalents and restricted cash at beginning of period $ 66,798 $ 250,129 Cash and cash equivalents at end of period $ 53,069 $ 478,391 Restricted cash at end of period — 7,199 Cash and cash equivalents and restricted cash at end of period $ 53,069 $ 485,590
Kilroy Realty, L.P. [Member]
Other Significant Noncash Transactions [Line Items]
Schedule of supplemental cash flows	Supplemental cash flow information is included as follows (in thousands): Three Months Ended March 31, 2018 2017 SUPPLEMENTAL CASH FLOWS INFORMATION: Cash paid for interest, net of capitalized interest of $13,051 and $9,829 as of March 31, 2018 and 2017, respectively $ 9,699 $ 18,206 NON-CASH INVESTING TRANSACTIONS: Accrual for expenditures for operating properties and development properties $ 57,155 $ 50,056 Tenant improvements funded directly by tenants $ 2,014 $ 7,416 NON-CASH FINANCING TRANSACTIONS: Accrual of distributions payable to common unitholders $ 43,512 $ 38,176 Accrual of distributions payable to preferred unitholders $ — $ 797
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, 2018 and 2017 . Three Months Ended March 31, 2018 2017 RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH: Cash and cash equivalents at beginning of period $ 57,649 $ 193,418 Restricted cash at beginning of period 9,149 56,711 Cash and cash equivalents and restricted cash at beginning of period $ 66,798 $ 250,129 Cash and cash equivalents at end of period $ 53,069 $ 478,391 Restricted cash at end of period — 7,199 Cash and cash equivalents and restricted cash at end of period $ 53,069 $ 485,590
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, 2018 and 2017 . Three Months Ended March 31, 2018 2017 RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH: Cash and cash equivalents at beginning of period $ 57,649 $ 193,418 Restricted cash at beginning of period 9,149 56,711 Cash and cash equivalents and restricted cash at beginning of period $ 66,798 $ 250,129 Cash and cash equivalents at end of period $ 53,069 $ 478,391 Restricted cash at end of period — 7,199 Cash and cash equivalents and restricted cash at end of period $ 53,069 $ 485,590

Organization, Ownership and B43

Organization, Ownership and Basis of Presentation (Details)	Mar. 31, 2018ft²	Mar. 31, 2018	Mar. 31, 2018project	Mar. 31, 2018tenant	Mar. 31, 2018building	Mar. 31, 2018number_of_residential_units	Mar. 31, 2018property	Dec. 31, 2017building
Stabilized office properties [Member]
Real Estate Properties [Line Items]
Number of Buildings					104		4
Rentable Square Feet (unaudited)	13,866,127
Number of Tenants | tenant				515
Percentage Occupied (unaudited)		94.30%
Percentage Leased (unaudited)		96.70%
Stabilized residential properties [Member]
Real Estate Properties [Line Items]
Number of Buildings | building								1
Percentage Occupied (unaudited)		83.00%
Number of Units | building								200
Development projects under construction [Member]
Real Estate Properties [Line Items]
Number of Buildings | project			5
Rentable Square Feet (unaudited)	2,106,000
Number of residential units | number_of_residential_units						237
Retail site [Member] | Development projects under construction [Member]
Real Estate Properties [Line Items]
Rentable Square Feet (unaudited)	120,000
Retail site [Member] | Production, Distribution and Repair (PDR) [Member]
Real Estate Properties [Line Items]
Rentable Square Feet (unaudited)	86,000

Organization, Ownership and B44

Organization, Ownership and Basis of Presentation (Details Textual) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)property_partnership	Mar. 31, 2017USD ($)	Mar. 31, 2018	Mar. 31, 2018project	Mar. 31, 2018a	Mar. 31, 2018USD ($)	Mar. 31, 2018building	Mar. 31, 2018VIE	Mar. 31, 2018property	Dec. 31, 2017USD ($)VIE
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Lease-up properties occupancy percentage	95.00%
Common general partnership interest in the Operating Partnership		97.90%	97.90%							97.90%
Common limited partnership interest in the Operating Partnership		2.10%	2.10%							2.10%
Number of VIEs | VIE								3		2
VIE assets						$ 543,500				$ 426,500
VIE liabilities						31,500				27,300
Noncontrolling interest in VIE						183,373				181,575
Ground leases, future minimum payments receivable						250,200
Kilroy Realty, L.P. [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Percentage of limited partnership interest owned by Operating Partnership	99.00%
101 First LLC and 303 Second LLC [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Common general partnership interest in the Operating Partnership			56.00%
Noncontrolling interest in VIE						177,200				175,400
Redwood LLC [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of Buildings | building							2
Common general partnership interest in the Operating Partnership			93.00%
Kilroy Realty Finance, Inc. [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Common general partnership interest in the Finance Partnership (percentage)	1.00%
San Francisco, California [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of Buildings | building							1
Properties held for sale [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of Buildings | property									0
Office properties [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of Buildings							104		4
Area of land | a					46
Office properties [Member] | Washington [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of Buildings | property									12
Development properties [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of Buildings | project				5
Number of property partnerships | property_partnership	3
Development properties [Member] | 101 First LLC and 303 Second LLC [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of property partnerships | property_partnership	2
Development properties [Member] | Washington [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of Buildings | property									1
Development sites [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of Buildings | project				6
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%
Real estate investment [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
VIE assets						$ 489,400				$ 382,100
Fixed-price contract [Member] | Parking revenue [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Revenue from contract with customer	$ 6,600	$ 6,700

Acquisitions (Details)

Acquisitions (Details) $ in Thousands	Jan. 31, 2018USD ($)ft²	Mar. 31, 2018USD ($)building
Assets
Land and improvements		$ 50,928
Buildings and improvements		59,123
Deferred leasing costs and acquisition-related intangible assets		4,470
Total assets acquired		114,521
Liabilities
Deferred revenue and acquisition-related intangible liabilities (3)		3,521
Total liabilities assumed		3,521
Net assets and liabilities acquired		111,000
Below market lease, acquired		$ 3,500
Acquired finite lived intangible liabilities weighted average useful life		9 years 9 months
In-place leases [Member]
Assets
Deferred leasing costs and acquisition-related intangible assets		$ 3,800
Liabilities
Acquired finite-lived intangible assets, weighted average useful life		2 years 7 months
Deferred leasing costs and acquisition-related intangible assets, net [Member]
Assets
Deferred leasing costs and acquisition-related intangible assets		$ 700
Liabilities
Acquired finite-lived intangible assets, weighted average useful life		3 years 6 months
345, 347 & 349 Oyster Point Boulevard, South San Francisco, CA [Member]
Schedule of Asset Acquisitions, by Acquisition [Line Items]
Number of Buildings | building		3
Rentable Square Feet (unaudited) | ft²	145,530
Purchase Price (in millions)	$ 111,000

Receivables (Details)

Receivables (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current Receivables, net
Current receivables	$ 19,630	$ 19,235
Allowance for uncollectible tenant receivables	(2,028)	(2,309)
Current receivables, net	17,602	16,926
Deferred Rent Receivables, net
Deferred rent receivables	254,969	249,629
Allowance for deferred rent receivables	(3,225)	(3,238)
Deferred rent receivables, net	$ 251,744	$ 246,391

Prepaid Expenses and Other As47

Prepaid Expenses and Other Assets, Net (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Furniture, fixtures and other long-lived assets, net	$ 38,541	$ 39,686
Note receivable	4,867	19,912
Prepaid expenses & acquisition deposits	63,916	55,108
Total prepaid expenses and other assets, net	107,324	$ 114,706
Proceeds received from repayment of note receivable (Note 3)	$ 15,100

Secured and Unsecured Debt of48

Secured and Unsecured Debt of the Operating Partnership - Unsecured Revolving Credit Facility and Term Loan Facility (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Debt Instrument [Line Items]
Borrowings on unsecured debt	$ 120,000,000	$ 0
Terms of the Credit Facility
Outstanding borrowings	50,000,000		$ 0
Kilroy Realty, L.P. [Member]
Debt Instrument [Line Items]
Borrowings on unsecured debt	120,000,000	$ 0
Terms of the Credit Facility
Outstanding borrowings	50,000,000		0
Unamortized deferred financing costs	14,300,000
Kilroy Realty, L.P. [Member] | Revolving credit facility [Member]
Debt Instrument [Line Items]
Contingent additional borrowings	600,000,000
Terms of the Credit Facility
Outstanding borrowings	50,000,000		0
Remaining borrowing capacity	700,000,000		750,000,000
Total borrowing capacity	$ 750,000,000		$ 750,000,000
Interest rate (percent)	2.72%		2.56%
Facility fee-annual rate (percent)	0.20%		0.20%
Maturity date	Jul. 1, 2022		Jul. 1, 2022
Unamortized deferred financing costs	$ 5,700,000		$ 6,000,000
London Interbank Offered Rate (LIBOR) [Member] | Kilroy Realty, L.P. [Member] | Revolving credit facility [Member]
Terms of the Credit Facility
Variable rate (percent)	1.00%		1.10%
$150 Million Term Loan Facility [Member] | Kilroy Realty, L.P. [Member] | Line of credit [Member]
Debt Instrument [Line Items]
Increase in borrowings	$ 30,000,000
Borrowings on unsecured debt	120,000,000
Terms of the Credit Facility
Outstanding borrowings	150,000,000		$ 0
Remaining borrowing capacity	$ 0		150,000,000
Total borrowing capacity			$ 150,000,000
Interest rate (percent)	2.90%		2.66%
Undawn facility fee-annual rate (percent)	0.20%		0.20%
Maturity date	Jul. 1, 2022		Jul. 1, 2022
Unamortized deferred financing costs	$ 1,100,000		$ 1,200,000
$150 Million Term Loan Facility [Member] | London Interbank Offered Rate (LIBOR) [Member] | Kilroy Realty, L.P. [Member] | Line of credit [Member]
Terms of the Credit Facility
Variable rate (percent)	1.10%		1.10%

Secured and Unsecured Debt of49

Secured and Unsecured Debt of the Operating Partnership - Debt Maturities (Details) - Kilroy Realty, L.P. [Member] $ in Thousands	Mar. 31, 2018USD ($)
Stated debt maturities and scheduled amortization payments, excluding debt discounts
Remaining 2,018	$ 2,706
2,019	76,309
2,020	255,137
2,021	5,342
2,022	205,554
Thereafter	2,018,469
Total debt	2,563,517
Unamortized debt issuance costs	(14,300)
Unsecured senior notes [Member]
Stated debt maturities and scheduled amortization payments, excluding debt discounts
Unamortized discount	(6,100)
Secured debt [Member]
Stated debt maturities and scheduled amortization payments, excluding debt discounts
Unamortized premium	$ 2,100

Secured and Unsecured Debt of50

Secured and Unsecured Debt of the Operating Partnership - Capitalized Interest and Loan Fees (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Capitalized Interest and Loan Fees [Line Items]
Interest expense	$ 13,498	$ 17,352
Kilroy Realty, L.P. [Member]
Capitalized Interest and Loan Fees [Line Items]
Gross interest expense	27,080	27,515
Capitalized interest and deferred financing costs	(13,582)	(10,163)
Interest expense	$ 13,498	$ 17,352

Stockholders' Equity of the C51

Stockholders' Equity of the Company (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2014
Common Stock of the Company [Abstract]
Common stock, shares issued (in shares)	98,839,708		98,620,333
Net proceeds from issuance of common stock	$ 0	$ 308,849,000
Issuance of Equity - at the market offering [Member]
Common Stock of the Company [Abstract]
At the market stock offering aggregate gross sales price of common stock				$ 300,000,000
Shares, issued	0
Common Stock [Member] | Issuance of Equity - at the market offering [Member]
Common Stock of the Company [Abstract]
At the market stock offering aggregate gross sales price of common stock	$ 200,100,000
Common stock, shares issued (in shares)	2,694,242
At the market stock offering remaining amount available for issuance	$ 99,900,000

Noncontrolling Interests on t52

Noncontrolling Interests on the Company's Consolidated Financial Statements - Common Units of the Operating Partnership (Details) - USD ($) $ / shares in Units, $ in Millions	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Noncontrolling Interest [Line Items]
Common general partnership interest in the Operating Partnership	97.90%	97.90%	97.90%
Common limited partnership interest in the Operating Partnership	2.10%	2.10%	2.10%
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Aggregate value upon redemption of outstanding noncontrolling common units	$ 146.1	$ 154.5
Kilroy Realty, L.P. [Member] | Common units [Member]
Noncontrolling Interest [Line Items]
Common units outstanding held by common limited partners	2,070,690	2,077,193	2,077,193

Partners' Capital of the Oper53

Partners' Capital of the Operating Partnership (Details) - shares	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
General Partners' Capital Account [Abstract]
Company owned general partnership interest	97.90%	97.90%	97.90%
Ownership interest of noncontrolling interest	2.10%	2.10%	2.10%
Kilroy Realty, L.P. [Member] | Common units [Member]
General Partners' Capital Account [Abstract]
Company owned common units in the Operating Partnership	98,839,708	98,620,333	98,275,048
Noncontrolling common units of the Operating Partnership	2,070,690	2,077,193	2,077,193

Share-Based Compensation (Detai

Share-Based Compensation (Details Textual) $ / shares in Units, $ in Millions	Feb. 14, 2018USD ($)$ / shares	Jan. 28, 2016shares	Feb. 28, 2017	Feb. 28, 2018shares	Mar. 31, 2018USD ($)planshares	Mar. 31, 2017USD ($)	Jan. 29, 2018$ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of share-based incentive compensation plans | plan					1
Share price | $ / shares							$ 70.37
Share-based compensation expense | $					$ 5.1	$ 6.2
Share-based compensation expense capitalized | $					1.5	$ 2
Share-based compensation not yet recognized | $					$ 41.3
Share-based compensation not yet recognized period of recognition					2 years 2 months
2018 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					50.00%
Vesting, Average debt to EBIDTA ratio, percentage of RSUs					100.00%
Vesting, Market measure, percentage of RSUs					50.00%
Number of shares issuable per RSU		1
Fair value RSUs granted | $	$ 10.8
Grant date fair value (in dollars per share) | $ / shares	$ 70.08
Share price | $ / shares	$ 66.46
Remaining expected life, including future volatility					5 years 10 months
Expected life					2 years 11 months
2018 Time-Based RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			3 years
Right to receive number of shares (in shares)					1
Fair value RSUs granted | $	$ 8.4
Kilroy Realty 2006 Incentive Award Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant					1,800,000
Chief Executive Officer [Member] | Kilroy Realty 2006 Incentive Award Plan [Member] | 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				282,038
Chief Executive Officer [Member] | Kilroy Realty 2006 Incentive Award Plan [Member] | 2018 Performance-Based RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares granted in period				158,205	158,205
Chief Executive Officer [Member] | Kilroy Realty 2006 Incentive Award Plan [Member] | 2018 Time-Based RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares granted in period				123,833

Share-Based Compensation (Det55

Share-Based Compensation (Details) - 2018 Performance-Based RSUs [Member]	3 Months Ended
	Mar. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected share price volatility	20.00%
Risk-free interest rate	2.37%
Expected life	2 years 11 months

Commitments and Contingencies (

Commitments and Contingencies (Details) $ in Millions	Mar. 31, 2018USD ($)
Commitments and Contingencies Disclosure [Abstract]
Commitments	$ 748.4
Accrued environmental remediation liabilities	$ 28.2

Fair Value Measurements and D57

Fair Value Measurements and Disclosures (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Fair value adjustment of marketable securities and deferred compensation plan liability
Net (loss) gain on marketable securities	$ (404)	$ 671
Fair Value (Level 1) [Member]
Assets and Liabilities Reported at Fair Value
Marketable securities	$ 21,572		$ 20,674

Fair Value Measurements and D58

Fair Value Measurements and Disclosures (Details 1) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Carrying value [Member] | Secured debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of debt, net	$ 339,501	$ 340,800
Carrying value [Member] | Unsecured debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of debt, net	2,155,794	2,006,263
Carrying value [Member] | Line of credit [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of debt, net	50,000	0
Fair value (level 2) [Member] | Fair value [Member] | Secured debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of debt, net	339,618	346,858
Fair value (level 2) [Member] | Fair value [Member] | Unsecured debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of debt, net	2,162,552	2,077,199
Fair value (level 2) [Member] | Fair value [Member] | Line of credit [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of debt, net	$ 50,058	$ 0

Net Income Available to Commo59

Net Income Available to Common Stockholders Per Share of the Company (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Numerator:
Net income attributable to Kilroy Realty Corporation	$ 36,246	$ 33,525
Total preferred dividends	0	(7,196)
Allocation to participating securities	(471)	(448)
Numerator for basic and diluted net income available to common stockholders	$ 35,775	$ 25,881
Denominator:
Basic weighted average vested shares outstanding (in shares)	98,744,220	97,388,137
Effect of dilutive securities (in shares)	469,390	630,020
Diluted weighted average vested shares and common share equivalents outstanding (in shares)	99,213,610	98,018,157
Basic earnings per share:
Net income available to common stockholders per share (in dollars per share)	$ 0.36	$ 0.27
Diluted earnings per share:
Net income available to common stockholders per share (in dollars per share)	$ 0.36	$ 0.26

Net Income Available to Commo60

Net Income Available to Common Unitholders Per Unit of the Operating Partnership (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Numerator:
Net income attributable to Kilroy Realty, L.P.	$ 36,246	$ 33,525
Total preferred dividends	0	(7,196)
Allocation to participating securities	(471)	(448)
Numerator for basic and diluted net income available to common stockholders	$ 35,775	$ 25,881
Denominator:
Basic weighted average vested shares outstanding (in shares)	98,744,220	97,388,137
Effect of dilutive securities (in units)	469,390	630,020
Diluted weighted average vested shares and common share equivalents outstanding (in shares)	99,213,610	98,018,157
Basic earnings per unit:
Net income available to common stockholders per share (in dollars per share)	$ 0.36	$ 0.27
Diluted earnings per unit:
Net income available to common stockholders per share (in dollars per share)	$ 0.36	$ 0.26
Kilroy Realty, L.P. [Member]
Numerator:
Net income attributable to Kilroy Realty, L.P.	$ 36,893	$ 34,054
Total preferred dividends	0	(7,196)
Allocation to participating securities	(471)	(448)
Numerator for basic and diluted net income available to common stockholders	$ 36,422	$ 26,410
Denominator:
Basic weighted average vested shares outstanding (in shares)	100,815,477	99,691,684
Effect of dilutive securities (in units)	469,390	630,020
Diluted weighted average vested shares and common share equivalents outstanding (in shares)	101,284,867	100,321,704
Basic earnings per unit:
Net income available to common stockholders per share (in dollars per share)	$ 0.36	$ 0.26
Diluted earnings per unit:
Net income available to common stockholders per share (in dollars per share)	$ 0.36	$ 0.26

Supplemental Cash Flow Inform61

Supplemental Cash Flow Information of the Company (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
SUPPLEMENTAL CASH FLOWS INFORMATION:
Cash paid for interest, net of capitalized interest of $13,051 and $9,829 as of March 31, 2018 and 2017, respectively	$ 9,699	$ 18,206
Interest capitalized	13,051	9,829
NON-CASH INVESTING TRANSACTIONS:
Accrual for expenditures for operating properties and development properties	57,155	50,056
Tenant improvements funded directly by tenants	2,014	7,416
NON-CASH FINANCING TRANSACTIONS:
Accrual of dividends and distributions payable to common stockholders and common unitholders	43,512	38,176
Accrual of dividends and distributions payable to preferred stockholders and preferred unitholders	0	797
Exchange of common units of the Operating Partnership into shares of the Company’s common stock	$ 244	$ 10,939

Supplemental Cash Flow Inform62

Supplemental Cash Flow Information of the Company - Reconciliation of cash and cash equivalents and restricted cash (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Supplemental Cash Flow Elements [Abstract]
Cash and cash equivalents at beginning of period	$ 57,649	$ 478,391	$ 193,418
Restricted cash at beginning of period	9,149	7,199	56,711
Cash and cash equivalents and restricted cash, beginning of period	66,798	485,590	250,129
Cash and cash equivalents at end of period	53,069	57,649	478,391
Restricted cash at end of period	0	9,149	7,199
Cash and cash equivalents and restricted cash, end of period	$ 53,069	$ 66,798	$ 485,590

Supplemental Cash Flow Inform63

Supplemental Cash Flow Information of the Operating Partnership (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
SUPPLEMENTAL CASH FLOWS INFORMATION:
Cash paid for interest, net of capitalized interest of $13,051 and $9,829 as of March 31, 2018 and 2017, respectively	$ 9,699	$ 18,206
Interest capitalized	13,051	9,829
NON-CASH INVESTING TRANSACTIONS:
Accrual for expenditures for operating properties and development properties	57,155	50,056
Tenant improvements funded directly by tenants	2,014	7,416
NON-CASH FINANCING TRANSACTIONS:
Accrual of distributions payable to common unitholders	43,512	38,176
Accrual of distributions payable to preferred unitholders	0	797
Kilroy Realty, L.P. [Member]
SUPPLEMENTAL CASH FLOWS INFORMATION:
Cash paid for interest, net of capitalized interest of $13,051 and $9,829 as of March 31, 2018 and 2017, respectively	9,699	18,206
Interest capitalized	13,051	9,829
NON-CASH INVESTING TRANSACTIONS:
Accrual for expenditures for operating properties and development properties	57,155	50,056
Tenant improvements funded directly by tenants	2,014	7,416
NON-CASH FINANCING TRANSACTIONS:
Accrual of distributions payable to common unitholders	43,512	38,176
Accrual of distributions payable to preferred unitholders	$ 0	$ 797

Supplemental Cash Flow Inform64

Supplemental Cash Flow Information of the Operating Partnership - Reconciliation of cash and cash equivalents and restricted cash (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Other Significant Noncash Transactions [Line Items]
Cash and cash equivalents at beginning of period	$ 57,649	$ 478,391	$ 193,418
Restricted cash at beginning of period	9,149	7,199	56,711
Cash and cash equivalents and restricted cash, beginning of period	66,798	485,590	250,129
Cash and cash equivalents at end of period	53,069	57,649	478,391
Restricted cash at end of period	0	9,149	7,199
Cash and cash equivalents and restricted cash, end of period	53,069	66,798	485,590
Kilroy Realty, L.P. [Member]
Other Significant Noncash Transactions [Line Items]
Cash and cash equivalents at beginning of period	57,649	478,391	193,418
Restricted cash at beginning of period	9,149	7,199	56,711
Cash and cash equivalents and restricted cash, beginning of period	66,798	485,590	250,129
Cash and cash equivalents at end of period	53,069	57,649	478,391
Restricted cash at end of period	0	9,149	7,199
Cash and cash equivalents and restricted cash, end of period	$ 53,069	$ 66,798	$ 485,590

Subsequent Events (Details)

Subsequent Events (Details) - USD ($) $ in Thousands	Apr. 18, 2018	Mar. 31, 2018	Mar. 31, 2017
Subsequent Event [Line Items]
Payment of dividend		$ 43,033	$ 217,643
Subsequent Event [Member]
Subsequent Event [Line Items]
Payment of dividend	$ 43,500