Kilroy Realty (KRC) 10-K 13 Feb 18 2017 Q4 Annual report Financial data

Document and Entity Information

Document and Entity Information Document - USD ($)	12 Months Ended
	Dec. 31, 2017	Feb. 09, 2018	Jun. 30, 2017
Entity Information [Line Items]
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-K
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q4
Amendment Flag	false
Entity Common Stock, Shares Outstanding		98,721,228
Entity Public Float			$ 7,367,936,410
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Kilroy Realty, L.P. [Member]
Entity Information [Line Items]
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-K
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q4
Amendment Flag	false
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
REAL ESTATE ASSETS (Notes 2, 3 and 4):
Land and improvements	$ 1,076,172	$ 1,108,971
Buildings and improvements	4,908,797	4,938,250
Undeveloped land and construction in progress	1,432,808	1,013,533
Total real estate assets held for investment	7,417,777	7,060,754
Accumulated depreciation and amortization	(1,264,162)	(1,139,853)
Total real estate assets held for investment, net	6,153,615	5,920,901
REAL ESTATE ASSETS AND OTHER ASSETS HELD FOR SALE, NET (Note 4)	0	9,417
CASH AND CASH EQUIVALENTS (Notes 4 and 22)	57,649	193,418
RESTRICTED CASH (Notes 4 and 22)	9,149	56,711
MARKETABLE SECURITIES (Notes 16 and 19)	20,674	14,773
CURRENT RECEIVABLES, NET (Note 6)	16,926	13,460
DEFERRED RENT RECEIVABLES, NET (Note 6)	246,391	218,977
DEFERRED LEASING COSTS AND ACQUISITION-RELATED INTANGIBLE ASSETS, NET (Notes 3 and 5)	183,728	208,368
PREPAID EXPENSES AND OTHER ASSETS, NET (Note 7)	114,706	70,608
TOTAL ASSETS	6,802,838	6,706,633
LIABILITIES:
Secured debt, net (Notes 8, 9 and 19)	340,800	472,772
Unsecured debt, net (Notes 8, 9 and 19)	2,006,263	1,847,351
Accounts payable, accrued expenses and other liabilities (Note 18)	249,637	202,391
Accrued dividends and distributions (Notes 13 and 27)	43,448	222,306
Deferred revenue and acquisition-related intangible liabilities, net (Notes 3, 5 and 10)	145,890	150,360
Rents received in advance and tenant security deposits	56,484	52,080
Liabilities and deferred revenue of real estate assets held for sale (Note 4)	0	56
Total liabilities	2,842,522	2,947,316
COMMITMENTS AND CONTINGENCIES (Note 18)
Preferred Stock, $.01 par value, 30,000,000 shares authorized,
Common stock, $.01 par value, 150,000,000 shares authorized, 98,620,333 and 93,219,439 shares issued and outstanding, respectively	986	932
Additional paid-in capital	3,822,492	3,457,649
Distributions in excess of earnings	(122,685)	(107,997)
Total stockholders’ equity	3,700,793	3,542,995
Noncontrolling Interests (Note 11):
Common units of the Operating Partnership	77,948	85,590
Noncontrolling interests in consolidated property partnerships (Note 2)	181,575	130,732
Total noncontrolling interests	259,523	216,322
Total equity	3,960,316	3,759,317
TOTAL LIABILITIES AND EQUITY/CAPITAL	6,802,838	6,706,633
Series G Preferred Stock [Member]
Preferred Stock, $.01 par value, 30,000,000 shares authorized,
Redeemable Preferred stock	0	96,155
Series H Preferred Stock [Member]
Preferred Stock, $.01 par value, 30,000,000 shares authorized,
Redeemable Preferred stock	$ 0	$ 96,256

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Variable Interest Entity Consolidated Carrying Amounts, Real Estate Assets, net	$ 187,254,000	$ 211,755,000
Common stock, shares outstanding	98,620,333	93,219,439
Common stock [Member]
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	98,620,333	93,219,439
Common stock, shares outstanding	98,620,333	93,219,439
Preferred Stock [Member]
Preferred stock, shares authorized	30,000,000	30,000,000
Preferred stock, par value	$ 0.01	$ 0.01
Series G Preferred Stock [Member]
Preferred stock, shares authorized	0	4,000,000
Preferred units, issued	0	4,000,000
Preferred stock, par value	$ 0	$ 0.01
Preferred stock, shares outstanding		4,000,000
Preferred stock dividend rate (percentage)	0.00%	6.875%
Preferred stock liquidation preference	$ 0	$ 100,000,000
Series H Preferred Stock [Member]
Preferred stock, shares authorized	0	4,000,000
Preferred units, issued	0	4,000,000
Preferred stock, par value	$ 0	$ 0.01
Preferred stock, shares outstanding		4,000,000
Preferred stock dividend rate (percentage)	0.00%	6.375%
Preferred stock liquidation preference	$ 0	$ 100,000,000

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
REVENUES:
Rental income	$ 633,896	$ 574,413	$ 525,355
Tenant reimbursements	76,559	61,079	53,774
Other property income (Note 18)	8,546	7,080	2,146
Total revenues	719,001	642,572	581,275
EXPENSES:
Property expenses	129,971	113,932	105,378
Real estate taxes	66,449	55,206	50,223
Provision for bad debts	3,269	0	545
Ground leases (Notes 5 and 18)	6,337	3,439	3,096
General and administrative expenses	60,581	57,029	48,265
Acquisition-related expenses (Note 2)	0	1,902	497
Depreciation and amortization (Notes 2 and 5)	245,886	217,234	204,294
Total expenses	512,493	448,742	412,298
OTHER (EXPENSES) INCOME:
Interest income and other net investment gains (Note 19)	5,503	1,764	243
Interest expense (Note 9)	(66,040)	(55,803)	(57,682)
Loss on early extinguishment of debt (Note 9)	(5,312)	0	0
Total other (expenses) income	(65,849)	(54,039)	(57,439)
INCOME FROM OPERATIONS BEFORE GAINS (LOSSES) ON SALES OF REAL ESTATE	140,659	139,791	111,538
Net gain (loss) on sales of land (Note 4)	449	(295)	17,116
Gains on sales of depreciable operating properties (Note 4)	39,507	164,302	109,950
NET INCOME	180,615	303,798	238,604
Net income attributable to noncontrolling common units of the Operating Partnership (Notes 2 and 11)	(3,223)	(6,635)	(4,339)
Net income attributable to noncontrolling interests in consolidated property partnerships (Notes 2 and 11)	(12,780)	(3,375)	(184)
Total income attributable to noncontrolling interests	(16,003)	(10,010)	(4,523)
NET INCOME ATTRIBUTABLE TO KILROY REALTY CORPORATION / KILROY REALTY, L.P.	164,612	293,788	234,081
Preferred dividends (Note 13)	(5,774)	(13,250)	(13,250)
Original issuance costs of redeemed preferred stock and preferred units	(7,589)	0	0
Total preferred dividends	(13,363)	(13,250)	(13,250)
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS/UNITHOLDERS	$ 151,249	$ 280,538	$ 220,831
Net income available to common stockholders per share - basic	$ 1.52	$ 3	$ 2.44
Net income available to common stockholders per share - diluted	$ 1.51	$ 2.97	$ 2.42
Weighted average shares of common stock outstanding – basic	98,113,561	92,342,483	89,854,096
Weighted average shares of common stock outstanding – diluted	98,727,331	93,023,034	90,395,775

Consolidated Statements of Equi

Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Total Stockholders' Equity	Preferred Stock [Member]	Common stock [Member]	Common Stock Additional Paid-in Capital [Member]	Common Stock Distributions in Excess of Earnings [Member]	Noncontrolling Interests - Common Units of the Operating Partnership [Member]
Beginning Balance at Dec. 31, 2014	$ 2,723,936	$ 2,666,210	$ 192,411	$ 863	$ 2,635,900	$ (162,964)	$ 57,726
Beginning Balance, shares at Dec. 31, 2014				86,259,684
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	238,604	234,081				234,081	4,523
Issuance of common stock	387,398	387,398		$ 56	387,342
Issuance of common stock, shares				5,640,033
Issuance of share-based compensation awards	1,692	1,692			1,692
Issuance of share-based compensation awards, shares
Non-cash amortization of share-based compensation	18,869	18,869			18,869
Exercise of stock options	14,573	14,573		$ 4	14,569
Exercise of stock options, shares				342,000
Repurchase of common stock and restricted stock units	(7,081)	(7,081)			(7,081)
Repurchase of common stock and restricted stock units, shares				(101,389)
Settlement of restricted stock units for shares of common stock	(1)	(1)			(1)
Settlement of restricted stock units for shares of common stock, shares				78,937
Exchange of common units of the Operating Partnership	0	1,223			1,223		(1,223)
Exchange of common units of the Operating Partnership, shares				39,425
Adjustment for noncontrolling interest	0	(4,619)			(4,619)		4,619
Contribution by noncontrolling interest in consolidated property partnership	474						474
Preferred dividends and distributions	(13,250)	(13,250)				(13,250)
Dividends declared per share of common stock and common unit	(130,628)	(128,129)				(128,129)	(2,499)
Ending Balance at Dec. 31, 2015	3,234,586	3,170,966	192,411	$ 923	3,047,894	(70,262)	63,620
Ending Balance, shares at Dec. 31, 2015				92,258,690
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	303,798	293,788				293,788	10,010
Issuance of common stock	31,117	31,117		$ 4	31,113
Issuance of common stock, shares				451,398
Issuance of share-based compensation awards	1,827	1,827			1,827
Non-cash amortization of share-based compensation	26,624	26,624			26,624
Exercise of stock options	12,208	12,208		$ 3	12,205
Exercise of stock options, shares				286,500
Repurchase of common stock and restricted stock units	(8,875)	(8,875)		$ (1)	(8,874)
Repurchase of common stock and restricted stock units, shares				(137,126)
Settlement of restricted stock units for shares of common stock	0	0		$ 1	(1)
Settlement of restricted stock units for shares of common stock, shares				109,044
Issuance of common units in connection with acquisition	48,033	0					48,033
Exchange of common units of the Operating Partnership	0	8,893		$ 2	8,891		(8,893)
Exchange of common units of the Operating Partnership, shares				250,933
Distributions to noncontrolling interests in consolidated property partnerships	(3,615)	0					(3,615)
Adjustment for noncontrolling interest	0	8,973			8,973		(8,973)
Contribution by noncontrolling interest in consolidated property partnership	453,449	328,997			328,997		124,452
Preferred dividends and distributions	(13,250)	(13,250)				(13,250)
Dividends declared per share of common stock and common unit	(326,585)	(318,273)				(318,273)	(8,312)
Ending Balance at Dec. 31, 2016	$ 3,759,317	3,542,995	192,411	$ 932	3,457,649	(107,997)	216,322
Ending Balance, shares at Dec. 31, 2016	93,219,439			93,219,439
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 180,615	164,612				164,612	16,003
Redemption of Series G & H Preferred stock	(200,000)	(200,000)	(192,411)			(7,589)
Issuance of common stock	326,058	326,058		$ 46	326,012
Issuance of common stock, shares				4,662,577
Issuance of share-based compensation awards	5,890	5,890			5,890
Non-cash amortization of share-based compensation	26,319	26,319			26,319
Exercise of stock options	12,179	12,179		$ 4	12,175
Exercise of stock options, shares				285,000
Repurchase of common stock and restricted stock units	(12,986)	(12,986)		$ (2)	(12,984)
Repurchase of common stock and restricted stock units, shares				(168,881)
Settlement of restricted stock units for shares of common stock	0	0		$ 3	(3)
Settlement of restricted stock units for shares of common stock, shares				317,848
Exchange of common units of the Operating Partnership	0	10,939		$ 3	10,936		(10,939)
Exchange of common units of the Operating Partnership, shares				304,350
Initial contributions from noncontrolling interest in consolidated property partnership, net of transaction costs	54,604	0					54,604
Distributions to noncontrolling interests in consolidated property partnerships	(16,542)	0					(16,542)
Adjustment for noncontrolling interest	0	(3,502)			(3,502)		3,502
Preferred dividends and distributions	(5,774)	(5,774)				(5,774)
Dividends declared per share of common stock and common unit	(169,364)	(165,937)				(165,937)	(3,427)
Ending Balance at Dec. 31, 2017	$ 3,960,316	$ 3,700,793	$ 0	$ 986	$ 3,822,492	$ (122,685)	$ 259,523
Ending Balance, shares at Dec. 31, 2017	98,620,333			98,620,333

Consolidated Statements of Equ6

Consolidated Statements of Equity (Parenthetical) - $ / shares	Dec. 30, 2016	Dec. 13, 2016	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Stockholders' Equity [Abstract]
Dividends declared per common share	$ 1.90	$ 1.90	$ 0.375	$ 0.375	$ 1.65	$ 3.375	$ 1.40

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 180,615	$ 303,798	$ 238,604
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of real estate assets and leasing costs	241,862	213,156	201,482
Depreciation of non-real estate furniture, fixtures and equipment	4,024	4,078	2,812
Increase in provision for bad debts	3,269	0	545
Non-cash amortization of share-based compensation awards (Note 15)	19,046	21,064	15,537
Non-cash amortization of deferred financing costs and debt discounts and premiums	3,247	2,720	1,853
Non-cash amortization of net below market rents (Note 5)	(8,528)	(7,166)	(8,449)
Gains on sales of depreciable operating properties (Note 4)	(39,507)	(164,302)	(109,950)
(Gain) loss on sales of land	(449)	295	(17,116)
Loss on early extinguishment of debt (Note 9)	5,312	0	0
Non-cash amortization of deferred revenue related to tenant-funded tenant improvements (Note 10)	(16,767)	(13,244)	(13,338)
Straight-line rents	(33,275)	(29,629)	(44,383)
Net change in other operating assets	(17,732)	(5,214)	(8,085)
Net change in other operating liabilities	5,895	19,498	12,496
Net cash provided by operating activities	347,012	345,054	272,008
CASH FLOWS FROM INVESTING ACTIVITIES:
Expenditures for development properties and undeveloped land	(397,440)	(351,012)	(407,969)
Expenditures for acquisitions of development properties and undeveloped land (Note 3)	(19,829)	(33,513)	(148,352)
Expenditures for operating properties and other capital assets	(88,425)	(111,961)	(99,557)
Expenditures for acquisitions of operating properties (Note 3)	0	(393,767)	0
Net proceeds received from dispositions (Note 4)	182,492	325,031	319,639
(Increase) decrease in acquisition-related deposits	(35,900)	1,902	1,998
Issuance of notes receivable	0	(16,100)	(3,000)
Net cash used in investing activities	(359,102)	(579,420)	(337,241)
CASH FLOWS FROM FINANCING ACTIVITIES:
Redemption of Series G and H Preferred stock (Note 13)	(200,000)	0	0
Net proceeds from issuance of common stock (Note 13)	326,058	31,117	387,398
Net proceeds from the issuance of unsecured debt (Note 9)	674,447	0	397,776
Repayments of unsecured debt (Note 9)	(519,024)	0	(325,000)
Borrowings on unsecured revolving credit facility	270,000	305,000	250,000
Repayments on unsecured revolving credit facility	(270,000)	(305,000)	(390,000)
Principal payments and repayments of secured debt (Note 9)	(130,371)	(74,140)	(159,766)
Proceeds from the issuance of secured debt (Note 9)	0	170,000	0
Financing costs	(11,500)	(2,159)	(4,814)
Repurchase of common stock and restricted stock units (Note 13)	(12,986)	(8,875)	(7,081)
Proceeds from exercise of stock options (Note 15)	12,179	12,208	14,573
Contributions from noncontrolling interests in consolidated property partnerships (Note 11)	54,604	453,449	474
Distributions to noncontrolling interests in consolidated property partnerships	(16,542)	(3,615)	0
Dividends and distributions paid to common stockholders and common unitholders	(340,697)	(137,444)	(126,839)
Dividends and distributions paid to preferred stockholders and preferred unitholders	(7,409)	(13,250)	(13,250)
Net cash (used in) provided by financing activities	(171,241)	427,291	23,471
Net (decrease) increase in cash and cash equivalents and restricted cash	(183,331)	192,925	(41,762)
Cash and cash equivalents and restricted cash, beginning of year	250,129	57,204	98,966
Cash and cash equivalents and restricted cash, end of year	$ 66,798	$ 250,129	$ 57,204

Consolidated Balance Sheets (KI

Consolidated Balance Sheets (KILROY REALTY, L.P.) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
REAL ESTATE ASSETS (Notes 2, 3 and 4):
Land and improvements	$ 1,076,172	$ 1,108,971
Buildings and improvements	4,908,797	4,938,250
Undeveloped land and construction in progress	1,432,808	1,013,533
Total real estate assets held for investment	7,417,777	7,060,754
Accumulated depreciation and amortization	(1,264,162)	(1,139,853)
Total real estate assets held for investment, net	6,153,615	5,920,901
REAL ESTATE ASSETS AND OTHER ASSETS HELD FOR SALE, NET (Note 4)	0	9,417
CASH AND CASH EQUIVALENTS (Notes 4 and 23)	57,649	193,418
RESTRICTED CASH (Notes 4 and 23)	9,149	56,711
MARKETABLE SECURITIES (Notes 16 and 19)	20,674	14,773
CURRENT RECEIVABLES, NET (Note 6)	16,926	13,460
DEFERRED RENT RECEIVABLES, NET (Note 6)	246,391	218,977
DEFERRED LEASING COSTS AND ACQUISITION-RELATED INTANGIBLE ASSETS, NET (Notes 3 and 5)	183,728	208,368
PREPAID EXPENSES AND OTHER ASSETS, NET (Note 7)	114,706	70,608
TOTAL ASSETS	6,802,838	6,706,633
LIABILITIES:
Secured debt, net (Notes 9 and 19)	340,800	472,772
Unsecured debt, net (Notes 9 and 19)	2,006,263	1,847,351
Accounts payable, accrued expenses and other liabilities (Note 18)	249,637	202,391
Accrued distributions (Notes 14 and 27)	43,448	222,306
Deferred revenue and acquisition-related intangible liabilities, net (Notes 3, 5 and 10)	145,890	150,360
Rents received in advance and tenant security deposits	56,484	52,080
Liabilities and deferred revenue of real estate assets held for sale (Note 4)	0	56
Total liabilities	2,842,522	2,947,316
COMMITMENTS AND CONTINGENCIES (Note 18)
Partners’ Capital:
TOTAL LIABILITIES AND EQUITY/CAPITAL	6,802,838	6,706,633
Kilroy Realty, L.P. [Member]
REAL ESTATE ASSETS (Notes 2, 3 and 4):
Land and improvements	1,076,172	1,108,971
Buildings and improvements	4,908,797	4,938,250
Undeveloped land and construction in progress	1,432,808	1,013,533
Total real estate assets held for investment	7,417,777	7,060,754
Accumulated depreciation and amortization	(1,264,162)	(1,139,853)
Total real estate assets held for investment, net	6,153,615	5,920,901
REAL ESTATE ASSETS AND OTHER ASSETS HELD FOR SALE, NET (Note 4)	0	9,417
CASH AND CASH EQUIVALENTS (Notes 4 and 23)	57,649	193,418
RESTRICTED CASH (Notes 4 and 23)	9,149	56,711
MARKETABLE SECURITIES (Notes 16 and 19)	20,674	14,773
CURRENT RECEIVABLES, NET (Note 6)	16,926	13,460
DEFERRED RENT RECEIVABLES, NET (Note 6)	246,391	218,977
DEFERRED LEASING COSTS AND ACQUISITION-RELATED INTANGIBLE ASSETS, NET (Notes 3 and 5)	183,728	208,368
PREPAID EXPENSES AND OTHER ASSETS, NET (Note 7)	114,706	70,608
TOTAL ASSETS	6,802,838	6,706,633
LIABILITIES:
Secured debt, net (Notes 9 and 19)	340,800	472,772
Unsecured debt, net (Notes 9 and 19)	2,006,263	1,847,351
Accounts payable, accrued expenses and other liabilities (Note 18)	249,637	202,391
Accrued distributions (Notes 14 and 27)	43,448	222,306
Deferred revenue and acquisition-related intangible liabilities, net (Notes 3, 5 and 10)	145,890	150,360
Rents received in advance and tenant security deposits	56,484	52,080
Liabilities and deferred revenue of real estate assets held for sale (Note 4)	0	56
Total liabilities	2,842,522	2,947,316
COMMITMENTS AND CONTINGENCIES (Note 18)
Partners’ Capital:
Common units, 98,620,333 and 93,219,439 held by the general partner and 2,077,193 and 2,381,543 held by common limited partners issued and outstanding, respectively	3,773,941	3,431,768
Total Partners’ Capital	3,773,941	3,624,179
Noncontrolling interests in consolidated property partnerships and subsidiaries (Notes 2 and 12)	186,375	135,138
Total capital	3,960,316	3,759,317
TOTAL LIABILITIES AND EQUITY/CAPITAL	6,802,838	6,706,633
Series G Cumulative Redeemable Preferred Unit [Member] | Kilroy Realty, L.P. [Member]
Partners’ Capital:
Preferred Units, Preferred Partners' Capital Accounts	0	96,155
Series H Cumulative Redeemable Preferred Unit [Member] | Kilroy Realty, L.P. [Member]
Partners’ Capital:
Preferred Units, Preferred Partners' Capital Accounts	$ 0	$ 96,256

Consolidated Balance Sheets (K9

Consolidated Balance Sheets (KILROY REALTY, L.P.) (Parenthetical) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Variable Interest Entity Consolidated Carrying Amounts, Real Estate Assets, net	$ 187,254,000	$ 211,755,000
Kilroy Realty, L.P. [Member] | Capital units [Member]
General Partners' Capital Account, Units Issued	98,620,333	93,219,439
General Partners' Capital Account, Units Outstanding	98,620,333	93,219,439
Limited Partners' Capital Account, Units Issued	2,077,193	2,381,543
Noncontrolling common units of the Operating Partnership	2,077,193	2,381,543
Kilroy Realty, L.P. [Member] | Series G Cumulative Redeemable Preferred Unit [Member]
Preferred units, issued	0	4,000,000
Preferred units outstanding	0	4,000,000
Preferred stock dividend rate (percentage)	0.00%	6.875%
Preferred stock liquidation preference	$ 0	$ 100,000,000
Kilroy Realty, L.P. [Member] | Series H Cumulative Redeemable Preferred Unit [Member]
Preferred units, issued	0	4,000,000
Preferred units outstanding	0	4,000,000
Preferred stock dividend rate (percentage)	0.00%	6.375%
Preferred stock liquidation preference	$ 0	$ 100,000,000

Consolidated Statements of Op10

Consolidated Statements of Operations (KILROY REALTY, L.P.) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
REVENUES:
Rental income	$ 633,896	$ 574,413	$ 525,355
Tenant reimbursements	76,559	61,079	53,774
Other property income (Note 18)	8,546	7,080	2,146
Total revenues	719,001	642,572	581,275
EXPENSES:
Property expenses	129,971	113,932	105,378
Real estate taxes	66,449	55,206	50,223
Provision for bad debts	3,269	0	545
Ground leases (Notes 5 and 18)	6,337	3,439	3,096
General and administrative expenses	60,581	57,029	48,265
Acquisition-related expenses (Note 2)	0	1,902	497
Depreciation and amortization (Notes 2 and 5)	245,886	217,234	204,294
Total expenses	512,493	448,742	412,298
OTHER (EXPENSES) INCOME:
Interest income and other net investment gains (Note 19)	5,503	1,764	243
Interest expense (Note 9)	(66,040)	(55,803)	(57,682)
Loss on early extinguishment of debt (Note 9)	(5,312)	0	0
Total other (expenses) income	(65,849)	(54,039)	(57,439)
Net gain (loss) on sales of land (Note 4)	449	(295)	17,116
Gains on sales of depreciable operating properties (Note 4)	39,507	164,302	109,950
NET INCOME	180,615	303,798	238,604
Net income attributable to noncontrolling interests in consolidated property partnerships and subsidiaries (Notes 2 and 12)	(16,003)	(10,010)	(4,523)
NET INCOME ATTRIBUTABLE TO KILROY REALTY CORPORATION / KILROY REALTY, L.P.	164,612	293,788	234,081
Original issuance costs of redeemed preferred stock and preferred units	(7,589)	0	0
Total preferred distributions	(13,363)	(13,250)	(13,250)
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS/UNITHOLDERS	$ 151,249	$ 280,538	$ 220,831
Net income available to common unitholders per unit (dollars per unit)	$ 1.52	$ 3	$ 2.44
Net income available to common unitholders per unit (dollars per unit)	$ 1.51	$ 2.97	$ 2.42
Weighted average common units outstanding - basic	98,113,561	92,342,483	89,854,096
Weighted average common units outstanding - diluted	98,727,331	93,023,034	90,395,775
Kilroy Realty, L.P. [Member]
REVENUES:
Rental income	$ 633,896	$ 574,413	$ 525,355
Tenant reimbursements	76,559	61,079	53,774
Other property income (Note 18)	8,546	7,080	2,146
Total revenues	719,001	642,572	581,275
EXPENSES:
Property expenses	129,971	113,932	105,378
Real estate taxes	66,449	55,206	50,223
Provision for bad debts	3,269	0	545
Ground leases (Notes 5 and 18)	6,337	3,439	3,096
General and administrative expenses	60,581	57,029	48,265
Acquisition-related expenses (Note 2)	0	1,902	497
Depreciation and amortization (Notes 2 and 5)	245,886	217,234	204,294
Total expenses	512,493	448,742	412,298
OTHER (EXPENSES) INCOME:
Interest income and other net investment gains (Note 19)	5,503	1,764	243
Interest expense (Note 9)	(66,040)	(55,803)	(57,682)
Loss on early extinguishment of debt (Note 9)	(5,312)	0	0
Total other (expenses) income	(65,849)	(54,039)	(57,439)
INCOME FROM OPERATIONS BEFORE GAINS (LOSSES) ON SALES OF REAL ESTATE	140,659	139,791	111,538
Net gain (loss) on sales of land (Note 4)	449	(295)	17,116
Gains on sales of depreciable operating properties (Note 4)	39,507	164,302	109,950
NET INCOME	180,615	303,798	238,604
Net income attributable to noncontrolling interests in consolidated property partnerships and subsidiaries (Notes 2 and 12)	(13,175)	(3,735)	(467)
NET INCOME ATTRIBUTABLE TO KILROY REALTY CORPORATION / KILROY REALTY, L.P.	167,440	300,063	238,137
Preferred distributions (Note 14)	(5,774)	(13,250)	(13,250)
Original issuance costs of redeemed preferred stock and preferred units	(7,589)	0	0
Total preferred distributions	(13,363)	(13,250)	(13,250)
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS/UNITHOLDERS	$ 154,077	$ 286,813	$ 224,887
Net income available to common unitholders per unit (dollars per unit)	$ 1.52	$ 2.99	$ 2.44
Net income available to common unitholders per unit (dollars per unit)	$ 1.51	$ 2.96	$ 2.42
Weighted average common units outstanding - basic	100,246,567	94,771,688	91,645,578
Weighted average common units outstanding - diluted	100,860,337	95,452,239	92,187,257

Consolidated Statements of Capi

Consolidated Statements of Capital (KILROY REALTY, L.P.) - USD ($) $ in Thousands	3 Months Ended				12 Months Ended
	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 32,540	$ 37,281	$ 35,418	$ 178,113	$ 180,615	$ 303,798	$ 238,604
Redemption of Series G & H Preferred stock					(200,000)
Issuance of common units in connection with acquisition						48,033
Non-cash amortization of share-based compensation					26,319	26,624	18,869
Settlement of restricted stock units for shares of common stock					0	0	(1)
Contribution by noncontrolling interest in consolidated subsidiary					54,604
Contribution by noncontrolling interest in consolidated subsidiary						453,449	474
Distributions to noncontrolling interests in consolidated property partnerships					(16,542)	(3,615)
Preferred dividends and distributions					(5,774)	(13,250)	(13,250)
Noncontrolling Interest In Consolidated Subsidiaries [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income					16,003	10,010	4,523
Issuance of common units in connection with acquisition						48,033
Contribution by noncontrolling interest in consolidated subsidiary					54,604
Contribution by noncontrolling interest in consolidated subsidiary						124,452	474
Distributions to noncontrolling interests in consolidated property partnerships					(16,542)	(3,615)
Kilroy Realty, L.P. [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		3,759,317		3,234,586	3,759,317	3,234,586	2,723,936
Net income	32,540	37,281	35,418	178,113	180,615	303,798	238,604
Redemption of Series G & H Preferred stock					(200,000)
Issuance of common units					326,058	31,117	387,398
Issuance of common units in connection with acquisition						48,033
Issuance of share-based compensation awards					5,890	1,827	1,692
Non-cash amortization of share-based compensation					26,319	26,624	18,869
Exercise of stock options					12,179	12,208	14,573
Repurchase of common units and restricted stock units					(12,986)	(8,875)	(7,081)
Settlement of restricted stock units for shares of common stock					0	0	(1)
Contribution by noncontrolling interest in consolidated subsidiary					54,604	453,449	474
Contribution by noncontrolling interest in consolidated subsidiary						(3,615)
Distributions to noncontrolling interests in consolidated property partnerships					(16,542)
Preferred dividends and distributions					(5,774)	(13,250)	(13,250)
Distributions declared per common unit					(169,364)	(326,585)	(130,628)
Ending balance	3,960,316		3,759,317		3,960,316	3,759,317	3,234,586
Kilroy Realty, L.P. [Member] | Total Partners Capital [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		3,624,179		3,224,020	3,624,179	3,224,020	2,714,311
Net income					167,440	300,063	238,137
Redemption of Series G & H Preferred stock					(200,000)
Issuance of common units					326,058	31,117	387,398
Issuance of common units in connection with acquisition						48,033
Issuance of share-based compensation awards					5,890	1,827	1,692
Non-cash amortization of share-based compensation					26,319	26,624	18,869
Exercise of stock options					12,179	12,208	14,573
Repurchase of common units and restricted stock units					(12,986)	(8,875)	(7,081)
Settlement of restricted stock units for shares of common stock						0	(1)
Contribution by noncontrolling interest in consolidated subsidiary						328,997
Preferred dividends and distributions					(5,774)	(13,250)	(13,250)
Distributions declared per common unit					(169,364)	(326,585)	(130,628)
Ending balance	3,773,941		3,624,179		3,773,941	3,624,179	3,224,020
Kilroy Realty, L.P. [Member] | Partners Capital Preferred Units [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		192,411		192,411	192,411	192,411	192,411
Redemption of Series G & H Preferred stock					(192,411)
Ending balance	0		192,411		0	192,411	192,411
Kilroy Realty, L.P. [Member] | Partners Capital Common Unit [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		$ 3,431,768		$ 3,031,609	$ 3,431,768	$ 3,031,609	$ 2,521,900
Beginning balance units		95,600,982		94,023,465	95,600,982	94,023,465	88,063,884
Net income					$ 167,440	$ 300,063	$ 238,137
Redemption of Series G & H Preferred stock					(7,589)
Issuance of common units					$ 326,058	$ 31,117	$ 387,398
Issuance of common units, units					4,662,577	451,398	5,640,033
Issuance of common units in connection with acquisition						$ 48,033
Issuance of common units in connection with acquisition, units						867,701
Issuance of share-based compensation awards					$ 5,890	$ 1,827	$ 1,692
Non-cash amortization of share-based compensation					26,319	26,624	18,869
Exercise of stock options					$ 12,179	$ 12,208	$ 14,573
Exercise of stock options, units					285,000	286,500	342,000
Repurchase of common units and restricted stock units					$ (12,986)	$ (8,875)	$ (7,081)
Repurchase of common units and restricted stock units, units					(168,881)	(137,126)	(101,389)
Settlement of restricted stock units for shares of common stock					$ 0	$ 0	$ (1)
Settlement of restricted stock units for shares of common stock units					317,848	109,044	78,937
Contribution by noncontrolling interest in consolidated subsidiary						$ 328,997
Preferred dividends and distributions					(5,774)	(13,250)	$ (13,250)
Distributions declared per common unit					(169,364)	(326,585)	(130,628)
Ending balance	$ 3,773,941		$ 3,431,768		$ 3,773,941	$ 3,431,768	$ 3,031,609
Ending balance units	100,697,526		95,600,982		100,697,526	95,600,982	94,023,465
Kilroy Realty, L.P. [Member] | Noncontrolling Interest In Consolidated Subsidiaries [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		$ 135,138		$ 10,566	$ 135,138	$ 10,566	$ 9,625
Net income					13,175	3,735	467
Contribution by noncontrolling interest in consolidated subsidiary					54,604	124,452	474
Contribution by noncontrolling interest in consolidated subsidiary						(3,615)
Distributions to noncontrolling interests in consolidated property partnerships					(16,542)
Ending balance	$ 186,375		$ 135,138		$ 186,375	$ 135,138	$ 10,566

Consolidated Statements of Ca12

Consolidated Statements of Capital (KILROY REALTY, L.P.) - Parenthetical - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Kilroy Realty, L.P. [Member]
Distributions declared per common unit	$ 1.65	$ 3.375	$ 1.40

Consolidated Statements of Ca13

Consolidated Statements of Cash Flows (KILROY REALTY, L.P.) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 180,615	$ 303,798	$ 238,604
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of real estate assets and leasing costs	241,862	213,156	201,482
Depreciation of non-real estate furniture, fixtures and equipment	4,024	4,078	2,812
Increase in provision for bad debts	3,269	0	545
Non-cash amortization of share-based compensation awards (Note 15)	19,046	21,064	15,537
Non-cash amortization of deferred financing costs and debt discounts and premiums	3,247	2,720	1,853
Non-cash amortization of net below market rents (Note 5)	(8,528)	(7,166)	(8,449)
Gains on sales of depreciable operating properties (Note 4)	(39,507)	(164,302)	(109,950)
(Gain) loss on sales of land	(449)	295	(17,116)
Loss on early extinguishment of debt (Note 9)	5,312	0	0
Non-cash amortization of deferred revenue related to tenant-funded tenant improvements (Note 10)	(16,767)	(13,244)	(13,338)
Straight-line rents	(33,275)	(29,629)	(44,383)
Net change in other operating assets	(17,732)	(5,214)	(8,085)
Net change in other operating liabilities	5,895	19,498	12,496
Net cash provided by operating activities	347,012	345,054	272,008
CASH FLOWS FROM INVESTING ACTIVITIES:
Expenditures for development properties and undeveloped land	(397,440)	(351,012)	(407,969)
Expenditures for acquisitions of development properties and undeveloped land (Note 3)	(19,829)	(33,513)	(148,352)
Expenditures for operating properties and other capital assets	(88,425)	(111,961)	(99,557)
Expenditures for acquisitions of operating properties (Note 3)	0	(393,767)	0
Net proceeds received from dispositions (Note 4)	182,492	325,031	319,639
(Increase) decrease in acquisition-related deposits	(35,900)	1,902	1,998
Issuance of notes receivable	0	(16,100)	(3,000)
Net cash used in investing activities	(359,102)	(579,420)	(337,241)
CASH FLOWS FROM FINANCING ACTIVITIES:
Redemption of Series G and H Preferred units (Note 14)	(200,000)	0	0
Net proceeds from issuance of common units (Note 14)	326,058	31,117	387,398
Net proceeds from the issuance of unsecured debt (Note 9)	674,447	0	397,776
Repayments of unsecured debt (Note 9)	(519,024)	0	(325,000)
Borrowings on unsecured revolving credit facility	270,000	305,000	250,000
Repayments on unsecured revolving credit facility	(270,000)	(305,000)	(390,000)
Principal payments and repayments of secured debt (Note 9)	(130,371)	(74,140)	(159,766)
Proceeds from the issuance of secured debt (Note 9)	0	170,000	0
Financing costs	(11,500)	(2,159)	(4,814)
Repurchase of common units and restricted stock units (Note 14)	(12,986)	(8,875)	(7,081)
Proceeds from exercise of stock options (Note 15)	12,179	12,208	14,573
Contributions from noncontrolling interests in consolidated property partnerships (Note 12)	54,604	453,449	474
Distributions to noncontrolling interests in consolidated property partnerships	(16,542)	(3,615)	0
Distributions paid to common unitholders	(340,697)	(137,444)	(126,839)
Distributions paid to preferred unitholders	(7,409)	(13,250)	(13,250)
Net cash (used in) provided by financing activities	(171,241)	427,291	23,471
Net (decrease) increase in cash and cash equivalents and restricted cash	(183,331)	192,925	(41,762)
Cash and cash equivalents and restricted cash, beginning of year	250,129	57,204	98,966
Cash and cash equivalents and restricted cash, end of year	66,798	250,129	57,204
Kilroy Realty, L.P. [Member]
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	180,615	303,798	238,604
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of real estate assets and leasing costs	241,862	213,156	201,482
Depreciation of non-real estate furniture, fixtures and equipment	4,024	4,078	2,812
Increase in provision for bad debts	3,269	0	545
Non-cash amortization of share-based compensation awards (Note 15)	19,046	21,064	15,537
Non-cash amortization of deferred financing costs and debt discounts and premiums	3,247	2,720	1,853
Non-cash amortization of net below market rents (Note 5)	(8,528)	(7,166)	(8,449)
Gains on sales of depreciable operating properties (Note 4)	(39,507)	(164,302)	(109,950)
(Gain) loss on sales of land	(449)	295	(17,116)
Loss on early extinguishment of debt (Note 9)	5,312	0	0
Non-cash amortization of deferred revenue related to tenant-funded tenant improvements (Note 10)	(16,767)	(13,244)	(13,338)
Straight-line rents	(33,275)	(29,629)	(44,383)
Net change in other operating assets	(17,732)	(5,214)	(8,085)
Net change in other operating liabilities	5,895	19,498	12,496
Net cash provided by operating activities	347,012	345,054	272,008
CASH FLOWS FROM INVESTING ACTIVITIES:
Expenditures for development properties and undeveloped land	(397,440)	(351,012)	(407,969)
Expenditures for acquisitions of development properties and undeveloped land (Note 3)	(19,829)	(33,513)	(148,352)
Expenditures for operating properties and other capital assets	(88,425)	(111,961)	(99,557)
Expenditures for acquisitions of operating properties (Note 3)	0	(393,767)	0
Net proceeds received from dispositions (Note 4)	182,492	325,031	319,639
(Increase) decrease in acquisition-related deposits	(35,900)	1,902	1,998
Issuance of notes receivable	0	(16,100)	(3,000)
Net cash used in investing activities	(359,102)	(579,420)	(337,241)
CASH FLOWS FROM FINANCING ACTIVITIES:
Redemption of Series G and H Preferred units (Note 14)	(200,000)	0	0
Net proceeds from issuance of common units (Note 14)	326,058	31,117	387,398
Net proceeds from the issuance of unsecured debt (Note 9)	674,447	0	397,776
Repayments of unsecured debt (Note 9)	(519,024)	0	(325,000)
Borrowings on unsecured revolving credit facility	270,000	305,000	250,000
Repayments on unsecured revolving credit facility	(270,000)	(305,000)	(390,000)
Principal payments and repayments of secured debt (Note 9)	(130,371)	(74,140)	(159,766)
Proceeds from the issuance of secured debt (Note 9)	0	170,000	0
Financing costs	(11,500)	(2,159)	(4,814)
Repurchase of common units and restricted stock units (Note 14)	(12,986)	(8,875)	(7,081)
Proceeds from exercise of stock options (Note 15)	12,179	12,208	14,573
Contributions from noncontrolling interests in consolidated property partnerships (Note 12)	54,604	453,449	474
Distributions to noncontrolling interests in consolidated property partnerships	(16,542)	(3,615)	0
Distributions paid to common unitholders	(340,697)	(137,444)	(126,839)
Distributions paid to preferred unitholders	(7,409)	(13,250)	(13,250)
Net cash (used in) provided by financing activities	(171,241)	427,291	23,471
Net (decrease) increase in cash and cash equivalents and restricted cash	(183,331)	192,925	(41,762)
Cash and cash equivalents and restricted cash, beginning of year	250,129	57,204	98,966
Cash and cash equivalents and restricted cash, end of year	$ 66,798	$ 250,129	$ 57,204

Organization and Ownership

Organization and Ownership	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Ownership	Organization and Ownership Kilroy Realty Corporation (the “Company”) is a self-administered real estate investment trust (“REIT”) active in premier office and mixed-use submarkets along the West Coast. We own, develop, acquire and manage real estate assets, consisting primarily of Class A properties in the coastal regions of 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 December 31, 2017 : Number of Buildings Rentable Square Feet (unaudited) Number of Tenants Percentage Occupied (unaudited) Percentage Leased (unaudited) Stabilized Office Properties 101 13,720,597 511 95.2 % 96.9 % Number of Number of Units 2017 Average Occupancy Stabilized Residential Property 1 200 70.2 % 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 December 31, 2017 . During the first quarter of 2017 , we added one development project to our stabilized office portfolio consisting of 365,359 rentable square feet in Hollywood, California. As of December 31, 2017 , the following properties were excluded from our stabilized portfolio. We did not have any redevelopment properties at December 31, 2017 . Number of Properties/Projects Estimated Rentable Square Feet (unaudited) Development projects under construction (1)(2) 4 1,800,000 _______________ (1) Estimated rentable square feet upon completion. (2) Includes 86,000 square feet of Production, Distribution, and Repair (“PDR”) space. Development projects under construction also include 96,000 square feet of retail space and 237 residential units at One Paseo - Phase I in addition to the estimated office rentable square feet noted above. Our stabilized portfolio also excludes our near-term and future development pipeline, which as of December 31, 2017 was comprised of six potential development sites, representing approximately 48 gross acres of undeveloped land. As of December 31, 2017 , 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. 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 December 31, 2017 , 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 December 31, 2017 , the Company owned an approximate 93% common equity interest in Redwood LLC. The remaining interests in all three property partnerships were owned by unrelated third parties. As of December 31, 2017 , 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 December 31, 2017 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.

Basis of Presentation and Signi

Basis of Presentation and Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Basis of Presentation and Significant Accounting Policies [Abstract]
Basis of Presentation and Significant Accounting Policies	Basis of Presentation and Significant Accounting Policies Basis of Presentation The consolidated financial statements of the Company include the consolidated financial position and results of operations of the Company, the Operating Partnership, 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. Effective January 1, 2017, the Company adopted Financial Accounting Standards Board (“FASB”) Accounting Standards Update (“ASU”) No. 2016-18 (“ASU 2016-18”) which requires that a statement of cash flows explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. The Company adopted ASU 2016-18 on a retrospective basis. Therefore, amounts generally described as restricted cash and restricted cash equivalents are included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the Company’s consolidated statements of cash flows for the years ended December 31, 2017 , 2016 and 2015 . As a result of the adoption of ASU 2016-18, the change in restricted cash is no longer presented as a separate line item within cash flows from investing activities on the Company’s consolidated statements of cash flows since such balances are now included in total cash at both the beginning and end of the reporting period. As a result, for the year ended December 31, 2016 , the Company had net cash used in investing activities of $579.4 million instead of net cash used in investing activities of $635.4 million as previously reported since the Company had an increase in restricted cash of $56.0 million during the year ended December 31, 2016 primarily due to $48.4 million of restricted cash that was held at qualified intermediaries to facilitate potential future Section1031 Exchanges. For the year ended December 31, 2015 , the Company had net cash used in investing activities of $337.2 million instead of net cash used in investing activities of $262.8 million as previously reported since the Company had a decrease in restricted cash of $65.2 million during the year ended December 31, 2015 primarily due to the release of $59.2 million of cash proceeds related to the completion of Section 1031 Exchanges in January 2015. In addition, expenditures for acquisitions of development properties and undeveloped land during the year ended December 31, 2015 increased by $9.2 million as a result of our adoption of ASU 2016-18 due to holdback funds released from escrow relating to previous year acquisitions. Also effective January 1, 2017, the Company adopted FASB ASU No. 2017-01 (“ASU 2017-01”) which clarifies the framework for determining whether an integrated set of assets and activities meets the definition of a business. The revised framework provides a screen for determining whether an integrated set of assets is a business combination or an asset acquisition and clarifies that when substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or a group of similar assets, the set of assets and activities is deemed not to meet the definition of a business. As a result of our adoption of the guidance, which we adopted on a prospective basis, the Company expects that most of our future acquisitions of operating properties and development properties that were previously accounted for as business combinations will instead be accounted for as asset acquisitions under the new guidance. In addition, we expect that most of the transaction costs associated with these future acquisitions will be capitalized as part of the purchase price of the acquisition instead of being expensed as incurred to acquisition-related expenses. The Company did not have any acquisitions of operating properties during the year ended December 31, 2017 . In addition, effective January 1, 2017, the Company adopted FASB ASU No. 2016-09 (“ASU 2016-09”) which simplified several aspects of the accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, and classification on the statement of cash flows. The adoption of this guidance did not have an impact on our consolidated financial statements or notes to our consolidated financial statements. Partially Owned Entities and Variable Interest Entities Effective January 1, 2016, the Company adopted FASB ASU No. 2015-02 (“ASU 2015-02”), which amended certain guidance with respect to the evaluation of Variable Interest Entities (“VIEs”) and when a reporting entity is required to consolidate certain legal entities. Specifically, the amendments: (i) modify the evaluation of whether limited partnerships and similar legal entities are VIEs or voting interest entities, (ii) eliminate the presumption that a general partner should consolidate a limited partnership, (iii) affect the consolidation analysis of reporting entities that are involved with VIEs, and (iv) provide a scope exception for certain entities. Under this guidance, effective January 1, 2016, the Operating Partnership was determined to be a VIE of the Company as the Operating Partnership is a limited partnership in which the common limited partners do not have substantive kick-out rights or participating rights. However, given that the Company was deemed to be the primary beneficiary of the Operating Partnership because the Company has the ability to control the activities that most significantly impact the Operating Partnership’s economic performance, the adoption of this new guidance and the conclusion that the Operating Partnership was a VIE did not have any impact on our consolidated financial statements since the conclusion to consolidate the Operating Partnership still applied. The Operating Partnership was the only new VIE identified as part of the adoption of the guidance as of January 1, 2016. At December 31, 2017 the consolidated financial statements of the Company included two VIEs in addition to the Operating Partnership: 100 First LLC and 303 Second LLC. At December 31, 2017 , the Company and the Operating Partnership were determined to be the primary beneficiaries of these two VIEs since we had the ability to control the activities that most significantly impact each of the VIEs’ economic performance. As of December 31, 2017 , the two VIEs’ total assets, liabilities and noncontrolling interests included on our consolidated balance sheet were 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. 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, 2016 , the consolidated financial statements of the Company included three VIEs in addition to the Operating Partnership: 100 First LLC, 303 Second LLC and entity established during the fourth quarter of 2016 to facilitate a transaction intended to qualify as a like-kind exchange pursuant to Section 1031 of the Code (“Section 1031 Exchange”). In January 2017, the Section 1031 Exchange was successfully completed and the entity established for the 1031 Exchange was no longer a VIE. At December 31, 2016 , the impact of consolidating the VIEs increased the Company’s total assets, liabilities and noncontrolling interests on our consolidated balance sheet by approximately $654.3 million (of which $588.6 million related to real estate held for investment on our consolidated balance sheet), approximately $166.1 million and approximately $124.3 million , respectively. The consolidated financial statements of the Operating Partnership included the same three VIEs at December 31, 2016 . Our accounting policy is to consolidate entities in which we have a controlling financial interest and significant decision making control over the entity's operations. In determining whether we have a controlling financial interest in a partially owned entity and the requirement to consolidate the accounts of that entity, we consider factors such as ownership interest, board representation, management representation, size of our investment (including loans), authority to control decisions, and contractual and substantive participating rights of the members. In addition to evaluating control rights, we consolidate entities in which the other members have no substantive kick-out rights to remove the Company as the managing member. Entities in which the equity investors do not have sufficient equity at risk to finance their endeavors without additional financial support or the holders of the equity investment at risk do not have a controlling financial interest are VIEs. We evaluate whether an entity is a VIE and whether we are the primary beneficiary. We are deemed to be the primary beneficiary of a VIE when we have the power to direct the activities of the VIE that most significantly impact the VIEs’ economic performance and the obligation to absorb losses or receive benefits that could potentially be significant to the VIE. If the requirements for consolidation are not met, the Company would account for investments under the equity method of accounting if we have the ability to exercise significant influence over the entity. Equity method investments would be initially recorded at cost and subsequently adjusted for our share of net income or loss and cash contributions and distributions each period. The Company did not have any equity method investments at December 31, 2017 or December 31, 2016 . Significant Accounting Policies Acquisitions Subsequent to our adoption of ASU No. 2017-01 on January 1, 2017, which was adopted on a prospective basis, acquisitions of operating properties and development and redevelopment opportunities generally no longer meet the definition of a business and are accounted for as asset acquisitions. For these asset acquisitions, we record the acquired tangible and intangible assets and assumed liabilities based on each asset’s and liability’s relative fair value at the acquisition date of the total purchase price plus any capitalized acquisition costs. We record the acquired tangible and intangible assets and assumed liabilities of acquisitions of operating properties and development and redevelopment opportunities that meet the accounting criteria to be accounted for as business combinations at fair value at the acquisition date. The acquired assets and assumed liabilities for an acquisition generally include but are not limited to (i) land and improvements, buildings and improvements, undeveloped land and construction in progress and (ii) identified tangible and intangible assets and liabilities associated with in-place leases, including tenant improvements, leasing costs, value of above-market and below-market operating leases and ground leases, acquired in-place lease values and tenant relationships, if any. Any debt assumed and equity (including common units of the Operating Partnership) issued in connection with a property acquisition is recorded at fair value on the date of acquisition. The fair value of land and improvements is derived from comparable sales of land and improvements within the same submarket and/or region. The fair value of buildings and improvements, tenant improvements and leasing costs considers the value of the property as if it was vacant as well as current replacement costs and other relevant market rate information. The fair value of the above-market or below-market component of an acquired in-place operating lease is based upon the present value (calculated using a market discount rate) of the difference between (i) the contractual rents to be paid pursuant to the lease over its remaining non-cancellable lease term and (ii) our estimate of the rents that would be paid using fair market rental rates and rent escalations at the date of acquisition measured over the remaining non-cancellable term of the lease for above-market operating leases and the initial non-cancellable term plus the term of any below-market fixed rate renewal options, if applicable, for below-market operating leases. Our below-market operating leases generally do not include fixed rate or below-market renewal options. The amounts recorded for above-market operating leases are included in deferred leasing costs and acquisition-related intangible assets, net on the balance sheet and are amortized on a straight-line basis as a reduction of rental income over the remaining term of the applicable leases. The amounts recorded for below-market operating leases are included in deferred revenue and acquisition-related intangible liabilities, net on the balance sheet and are amortized on a straight-line basis as an increase to rental income over the remaining term of the applicable leases plus the term of any below-market fixed rate renewal options, if applicable. The amortization of the below-market ground lease obligation is recorded as an increase to ground lease expense in the consolidated statements of operations for the periods presented. The amortization of the above-market ground lease obligation is recorded as a decrease to ground lease expense in the consolidations statements of operations for the periods presented. The fair value of acquired in-place leases is derived based on our assessment of lost revenue and costs incurred for the period required to lease the “assumed vacant” property to the occupancy level when purchased. The amount recorded for acquired in-place leases is included in deferred leasing costs and acquisition-related intangible assets, net on the balance sheet and amortized as an increase to depreciation and amortization expense over the remaining term of the applicable leases. Fully amortized intangible assets are written off each quarter. Subsequent to our adoption of “ASU 2017-01” on January 1, 2017, transaction costs associated with our acquisitions are capitalized as part of the purchase price of the acquisition. Prior to our adoption of “ASU 2017-01,” costs associated with all operating property acquisitions and those development and redevelopment acquisitions that met the criteria to be accounted for as business combinations were expensed as incurred and costs associated with development acquisitions accounted for as asset acquisitions were capitalized as part of the cost of the asset. Operating Properties Operating properties are generally carried at historical cost less accumulated depreciation. Properties held for sale are reported at the lower of the carrying value or the fair value less estimated cost to sell. The cost of operating properties includes the purchase price or development costs of the properties. Costs incurred for the renovation and betterment of the operating properties are capitalized to our investment in that property. Maintenance and repairs are charged to expense as incurred. When evaluating properties to be held and used for potential impairment, we first evaluate whether there are any indicators of impairment for any of our properties. If any impairment indicators are present for a specific property, we then perform an undiscounted cash flow analysis and compare the net carrying amount of the property to the property’s estimated undiscounted future cash flow over the anticipated holding period. If the estimated undiscounted future cash flow is less than the net carrying amount of the property, we then perform an impairment loss calculation to determine if the fair value of the property is less than the net carrying value of the property. Our impairment loss calculation compares the net carrying amount of the property to the property’s estimated fair value, which may be based on estimated discounted future cash flow calculations or third-party valuations or appraisals. We would recognize an impairment loss if the asset’s net carrying amount exceeds the asset’s estimated fair value. If we were to recognize an impairment loss, the estimated fair value of the asset (less costs to sell for assets held for sale) would become its new cost basis. For a depreciable long-lived asset, the new cost basis would be depreciated (amortized) over the remaining useful life of that asset. Cost Capitalization All costs clearly associated with the development, redevelopment and construction of a property are capitalized as project costs, including internal compensation costs. In addition, the following costs are capitalized as project costs during periods in which activities necessary to prepare development and redevelopment properties for their intended use are in progress: pre-construction costs essential to the development of the property, interest, real estate taxes and insurance. • For office development and redevelopment properties that are pre-leased, we cease capitalization when revenue recognition commences, which is upon substantial completion of tenant improvements deemed to be the Company's asset for accounting purposes. • For office development and redevelopment properties that are not pre-leased, we may not immediately build out the tenant improvements. Therefore, we cease capitalization when revenue recognition commences upon substantial completion of the tenant improvements deemed to be the Company's asset for accounting purposes, but in any event, no later than one year after the cessation of major construction activities. We also cease capitalization on a development or redevelopment property when activities necessary to prepare the property for its intended use have been suspended. • For office development or redevelopment properties with multiple tenants and staged leasing, we cease capitalization and begin depreciation on the portion of the development or redevelopment property for which revenue recognition has commenced. • For residential development properties, we cease capitalization when the property is substantially complete and available for occupancy. Once major construction activity has ceased and the development or redevelopment property is in the lease-up phase, the costs capitalized to construction in progress are transferred to land and improvements, buildings and improvements, and deferred leasing costs on our consolidated balance sheets as the historical cost of the property. Depreciation and Amortization of Buildings and Improvements The costs of buildings and improvements and tenant improvements are depreciated using the straight-line method of accounting over the estimated useful lives set forth in the table below. Depreciation expense for buildings and improvements for the three years ended December 31, 2017 , 2016 , and 2015 was $190.5 million , $172.0 million , and $159.5 million , respectively. Asset Description Depreciable Lives Buildings and improvements 25 – 40 years Tenant improvements 1 – 20 years (1) ________________________ (1) Tenant improvements are amortized over the shorter of the lease term or the estimated useful life. Real Estate Assets Held for Sale, Dispositions and Discontinued Operations A real estate asset is classified as held for sale when certain criteria are met, including but not limited to the availability of the asset for immediate sale, the existence of an active program to locate a buyer and the probable sale or transfer of the asset within one year. If such criteria are met, we present the applicable assets and liabilities related to the real estate asset held for sale, if material, separately on the balance sheet and we would cease to record depreciation and amortization expense. Real estate assets held for sale are reported at the lower of their carrying value or their estimated fair value less the estimated costs to sell. As of December 31, 2017 , we did not have any properties classified as held for sale. As of December 31, 2016 , we classified one operating property located in San Diego, California as held for sale. Effective January 1, 2015, the Company adopted FASB ASU No. 2014-08 (“ASU 2014-08”), which changed the criteria for reporting discontinued operations while enhancing disclosures in this area. Under the guidance, only property disposals representing a strategic shift that has (or will have) a major effect on an entity’s operations and financial results, such as a major line of business, a major geographical area or a major equity investment, are required to be presented as discontinued operations. If we were to determine that the property disposition represents a strategic shift, the revenues, expenses and net gain (loss) on dispositions of the property would be recorded in discontinued operations for all periods presented through the date of the applicable disposition. The Company adopted and applied the new guidance on a prospective basis as required by ASU 2014-08. In accordance with this guidance, the operations of eleven , six and ten properties sold during the years ended December 31, 2017 , December 31, 2016 and December 31, 2015 , respectively, are presented in continuing operations as they did not represent a strategic shift in the Company’s operations and financial results. The net gains (losses) on dispositions of non-depreciable real estate property, including land, are reported in the consolidated statements of operations as gains (losses) on sale of land within continuing operations in the period the land is sold. Revenue Recognition We recognize revenue from rent, tenant reimbursements, parking and other revenue once all of the following criteria are met: (i) the agreement has been fully executed and delivered, (ii) services have been rendered, (iii) the amount is fixed or determinable and (iv) the collectability of the amount is reasonably assured. Minimum annual rental revenues are recognized in rental revenues on a straight-line basis over the non-cancellable term of the related lease. Rental revenue recognition commences when the tenant takes possession or controls the physical use of the leased space. In order for the tenant to take possession, the leased space must be substantially complete and ready for its intended use. In order to determine whether the leased space is substantially ready for its intended use, we begin by determining whether the Company or the tenant owns the tenant improvements. When we conclude that the Company is the owner of tenant improvements, rental revenue recognition begins when the tenant takes possession of the finished space, which is generally when Company owned tenant improvements are substantially complete. In certain instances, when we conclude that the Company is not the owner (the tenant is the owner) of tenant improvements, rental revenue recognition begins when the tenant takes possession of or controls the space. When we conclude that the Company is the owner of tenant improvements, we record the cost to construct the tenant improvements, including costs paid for or reimbursed by the tenants, as a capital asset. For these tenant improvements, we record the amount funded by or reimbursed by the tenants as deferred revenue, which is amortized on a straight-line basis as additional rental income over the term of the related lease. When we conclude that the tenant is the owner of tenant improvements for accounting purposes, we record our contribution towards those improvements as a lease incentive, which is included in deferred leasing costs and acquisition-related intangible assets, net on our consolidated balance sheets and amortized as a reduction to rental income on a straight-line basis over the term of the lease. For residential properties, we commence revenue recognition upon occupancy of the units by the tenants. Residential rental revenue is recognized on a straight-line basis over the term of the related lease, net of any concessions. Tenant Reimbursements Reimbursements from tenants, consisting of amounts due from tenants for common area maintenance, real estate taxes and other recoverable costs, are recognized as revenue in the period the recoverable costs are incurred. Tenant reimbursements are recognized and recorded on a gross basis, as we are generally the primary obligor with respect to purchasing goods and services from third-party suppliers, have discretion in selecting the supplier, and have credit risk. Other Property Income Other property income primarily includes amounts recorded in connection with lease terminations, tenant bankruptcy settlement payments, broken deal income and property damage settlement related payments. Lease termination fees are amortized over the remaining lease term, if applicable. If there is no remaining lease term, they are recognized when received and realized. Other property income also includes miscellaneous income from tenants, such as fees related to the restoration of leased premises to their original condition and fees for late rental payments. Allowances for Uncollectible Tenant and Deferred Rent Receivables We carry our current and deferred rent receivables net of allowances for uncollectible amounts. Our determination of the adequacy of these allowances is based primarily upon evaluations of individual receivables, current economic conditions, and other relevant factors. The allowances are increased or decreased through the provision for bad debts on our consolidated statements of operations. Cash and Cash Equivalents We consider all highly-liquid investments with original maturities of three months or less to be cash equivalents. Restricted Cash Restricted cash consists of cash proceeds from dispositions that are temporarily held at qualified intermediaries for purposes of facilitating potential Section 1031 Exchanges and cash held in escrow related to acquisition and disposition holdbacks. Restricted cash also includes cash held as collateral to provide credit enhancement for the Operating Partnership’s mortgage debt, including cash reserves for capital expenditures, tenant improvements and property taxes. As of December 31, 2017 , we did not have any restricted cash held at qualified intermediaries for the purpose of facilitating Section 1031 Exchanges. As of December 31, 2016 , we had $48.4 million restricted cash held at qualified intermediaries for the purpose of facilitating Section 1031 Exchanges. In January 2017, the Section 1031 Exchange was completed and the cash was released from the qualified intermediary. Marketable Securities / Deferred Compensation Plan Marketable securities reported in our consolidated balance sheets represent the assets held in connection with the Kilroy Realty Corporation 2007 Deferred Compensation Plan (the “Deferred Compensation Plan”) (see Note 16 “Employee Benefit Plans” for additional information). The Deferred Compensation Plan assets are held in a limited rabbi trust and invested in various mutual and money market funds. As a result, the marketable securities are treated as trading securities for financial reporting purposes and are adjusted to fair value at the end of each accounting period, with the corresponding gains and losses recorded in interest income and other net investment gains. At the time eligible management employees (“Participants”) defer compensation or earn mandatory Company contributions, or if we were to make a discretionary contribution, we record compensation cost and a corresponding deferred compensation plan liability, which is included in accounts payable, accrued expenses, and other liabilities on our consolidated balance sheets. This liability is adjusted to fair value at the end of each accounting period based on the performance of the benchmark funds selected by each Participant, and the impact of adjusting the liability to fair value is recorded as an increase or decrease to compensation cost. The impact of adjusting the deferred compensation plan liability to fair value and the changes in the value of the marketable securities held in connection with the Deferred Compensation Plan generally offset and therefore do not significantly impact net income. Deferred Leasing Costs Costs incurred in connection with successful property leasing are capitalized as deferred leasing costs and classified as investing activities in the statement of cash flows. Deferred leasing costs consist primarily of leasing commissions and also include certain internal payroll costs and lease incentives, which are amortized using the straight-line method of accounting over the lives of the leases which generally range from one to 20 years. We reevaluate the remaining useful lives of leasing costs as the creditworthiness of our tenants and economic and market conditions change. If we determine that the estimated remaining life of a lease has changed, we adjust the amortization period accordingly. Fully amortized deferred leasing costs are written off each quarter. Deferred Financing Costs Financing costs related to the origination or assumption of long-term debt are deferred and generally amortized using the straight-line method of accounting, which approximates the effective interest method, over the contractual terms of the applicable financings. Fully amortized deferred financing costs are written off when the corresponding financing is repaid. Debt Discounts and Premiums Original issuance debt discounts and discounts/premiums related to recording debt acquired in connection with operating property acquisitions at fair value are generally amortized and accreted on a straight-line basis, which approximates the effective interest method. Discounts are recorded as additional interest expense from date of issuance or acquisition through the contractual maturity date of the related debt. Premiums are recorded as a reduction to interest expense from the date of issuance or acquisition through the contractual maturity date of the related debt. Noncontrolling Interests - Common Units of the Operating Partnership in the Company's Consolidated Financial Statements Common units of the Operating Partnership within noncontrolling interests in the Company’s consolidated financial statements represent the common limited partnership interests in the Operating Partnership not held by the Company (“noncontrolling common units”). Noncontrolling common units are presented in the equity section of the Company’s consolidated balance sheets and are reported at their proportionate share of the net assets of the Operating Partnership. Noncontrolling interests with redemption provisions that permit the issuer to settle in either cash or shares of common stock must be further evaluated to determine whether equity or temporary equity classification on the balance sheet is appropriate. Since the common units contain such a provision, we evaluated the accounting guidance and determined that the common units qualify for equity presentation in the Company’s consolidated financial statements. Net income attributable to noncontrolling common units is allocated based on their relative ownership percentage of the Operating Partnership during the reported period. The noncontrolling interest ownership percentage is determined by dividing the number of noncontrolling common units by the total number of common units outstanding. The issuance or redemption of additional shares of common stock or common units results in changes to the noncontrolling interest percentage as well as the total net assets of the Company. As a result, all equity transactions result in an allocation between equity and the noncontrolling interest in the Company’s consolidated balance sheets and statements of equity to account for the changes in the noncontrolling interest ownership percentage as well as the change in total net assets of the Company. Noncontrolling Interests in Consolidated Property Partnerships Noncontrolling interests in consolidated property partnerships represent the equity interests held by unrelated third parties in our three consolidated property partnerships (see Note 11 “Noncontrolling Interests on the Company’s Consolidated Financial Statements” and see Note 12 “Noncontrolling Interests on the Operating Partnership

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Acquisitions	Acquisitions Operating Property Acquisitions We did not acquire any operating properties during the year ended December 31, 2017 . During the year ended December 31, 2016 we acquired the seven operating properties listed below in three transactions with unrelated third parties. Property Date of Acquisition Number of Buildings Rentable Square Feet (unaudited) Occupancy as of December 31, 2016 (unaudited) Purchase Price (in millions) (1) 2016 Acquisitions 1290-1300 Terra Bella Avenue, Mountain View, CA (2) June 8, 2016 1 114,175 100.0% $ 55.4 8560-8590 West Sunset Blvd., West Hollywood, CA (3) December 7, 2016 4 178,699 87.5% 209.2 1701 Page Mill Rd. and 3150 Porter Dr., Palo Alto, CA (4) December 19, 2016 2 165,585 100.0% 130.0 Total (5) 7 458,459 $ 394.6 ________________________ (1) Excludes acquisition-related costs and non-lease related accrued liabilities assumed. Includes assumed unpaid leasing commissions and tenant improvements. (2) In connection with this acquisition, the Company assumed $0.2 million in accrued liabilities that are not included in the purchase price above. (3) This acquisition encompasses a 10-story office tower, three retail buildings, a four-level subterranean parking structure and three billboards. In connection with this acquisition, the Company assumed $0.1 million in accrued liabilities that are not included in the purchase price above. (4) In connection with this acquisition, the Company entered into a long-term ground lease expiring in December 2067. (5) The results of operations for the properties acquired during 2016 contributed $5.2 million and $1.7 million to revenue and net income from continuing operations, respectively, for the year ended December 31, 2016 . The related assets, liabilities and results of operations of the acquired properties are included in the consolidated financial statements as of the date of acquisition. The following table summarizes the estimated fair values of the assets acquired and liabilities assumed at the respective acquisition dates for our 2016 operating property acquisitions: Acquisitions Total 2016 Acquisitions (1) Assets (in thousands) Land and improvements $ 120,110 Buildings and improvements (2) 259,301 Deferred leasing costs and acquisition-related intangible assets (3) 33,529 Total assets acquired 412,940 Liabilities Accounts payable, accrued expenses and other liabilities 1,122 Deferred revenue and acquisition-related intangible liabilities (4) 18,050 Total liabilities assumed 19,172 Net assets and liabilities acquired $ 393,768 _______________ (1) The purchase price of the three acquisitions completed during the year ended December 31, 2016 were individually less than 5% and in aggregate less than 10% of the Company’s total assets as of December 31, 2015 . (2) Represents buildings, building improvements and tenant improvements. (3) Represents in-place leases (approximately $27.1 million with a weighted average amortization period of 3.9 years), above-market leases (approximately $0.6 million with weighted average amortization period of 15.8 years) and leasing commissions (approximately $5.8 million with a weighted average amortization period of 5.1 years). (4) Represents below-market leases (approximately $18.1 million with a weighted average amortization period of 8.4 years) Development Project Acquisitions On October 10, 2017 , the Company completed the acquisition of a 1.2 acre development site located in the Little Italy neighborhood of downtown San Diego, California in three separate transactions from separate unrelated third parties for a total purchase price of $19.4 million and the assumption of $1.4 million of accrued liabilities. During the year ended December 31, 2016 we acquired an approximately 1.75 acre development site located at 610-620 Brannan Street in San Francisco, California from an unrelated third party. This land parcel is immediately adjacent to our Flower Mart project in the SOMA submarket of San Francisco. The acquisition was funded through $31.0 million in cash and the issuance of 867,701 common units in the Operating Partnership valued at approximately $48.0 million (see Note 14). In addition, the Company paid $2.4 million in seller transaction costs and recorded $4.7 million in accrued liabilities in connection with this acquisition. Acquisition Costs During the years ended December 31, 2017 , 2016 , and 2015 , we capitalized $4.6 million , $0.5 million , and $1.1 million , respectively, of acquisition costs. During the years ended December 31, 2016 and 2015 , we expensed $1.9 million and $0.5 million of acquisition costs, respectively.

Dispositions and Real Estate As

Dispositions and Real Estate Assets Held for Sale	12 Months Ended
	Dec. 31, 2017
Discontinued Operations and Disposal Groups [Abstract]
Dispositions and Real Estate Assets Held for Sale	Dispositions and Real Estate Assets Held for Sale Operating Property Dispositions The following table summarizes the operating properties sold during the years ended December 31, 2017 , 2016 and 2015 : Location Month of Disposition Number of Buildings Rentable Square Feet (unaudited) Sales Price (in millions) (1) 2017 Dispositions 5717 Pacific Center Boulevard, San Diego, CA (2) January 1 67,995 $ 12.1 Sorrento Mesa and Mission Valley Properties (3) September 10 675,143 174.5 Total 2017 Dispositions 11 743,138 $ 186.6 2016 Dispositions Torrey Santa Fe Properties (4) January 4 465,812 $ 262.3 4930, 4939 & 4955 Directors Place, San Diego, CA (5) July 2 136,908 49.0 Total 2016 Dispositions 6 602,720 $ 311.3 2015 Dispositions 15050 NE 36th Street, Redmond, WA April 1 122,103 $ 51.2 San Diego Properties - Tranches 1 and 2 (6) April/July 9 924,291 258.0 Total 2015 Dispositions 10 1,046,394 $ 309.2 __________________ (1) Represents gross sales price before the impact of broker commissions and closing costs. (2) This property was classified as held for sale at December 31, 2016 . (3) The Sorrento Mesa and Mission Valley Properties includes the following properties: 10390, 10394, 10398, 10421, 10445 and 10455 Pacific Center Court, 2355, 2365, 2375 and 2385 Northside Drive and Pacific Corporate Center - Lot 8, a 5.0 acre undeveloped land parcel. We recognized a gain on sale of land of $0.4 million related to the sale of Pacific Corporate Center - Lot 8 during the year ended December 31, 2017. (4) The Torrey Santa Fe Properties include the following properties: 7525, 7535, 7545 and 7555 Torrey Santa Fe. These properties were classified as held for sale at December 31, 2015 . (5) Includes two operating properties totaling 136,908 rentable square feet and a 7.0 acre undeveloped land parcel. (6) The San Diego Properties - Tranche 1 includes the following properties: 10770 Wateridge Circle, 6200 and 6220 Greenwich Drive. The San Diego Properties - Tranche 2 includes the following properties: 6260, 6290, 6310, 6340, 6350 Sequence Drive and 4921 Directors Place. The total gains on the sales of the properties sold during the years ended December 31, 2017 , 2016 and 2015 were $39.5 million , $164.3 million and $110.0 million , respectively. Operating Properties Held for Sale We did not have any properties classified as held for sale as of December 31, 2017 . As of December 31, 2016 , the property listed below was classified as held for sale. Properties Submarket Property Type Number of Buildings Rentable Square Feet (unaudited) 2016 Held for Sale 5717 Pacific Center Drive (1) Sorrento Mesa Office 1 67,995 __________________ (1) In January 2017, the Company completed the sale of this property for a total sales price of $12.1 million as indicated on the table above. The major classes of assets and liabilities of the property held for sale as of December 31, 2016 were as follows: December 31, 2016 Real estate assets and other assets held for sale (in thousands) Land and improvements $ 2,693 Buildings and improvements 10,500 Total real estate held for sale 13,193 Accumulated depreciation and amortization (3,900 ) Total real estate held for sale, net 9,293 Prepaid expenses and other assets, net 124 Real estate and other assets held for sale, net $ 9,417 Liabilities of real estate assets held for sale Accounts payable, accrued expenses and other liabilities $ 56 Liabilities of real estate assets held for sale $ 56 Land Dispositions The following table summarizes the land dispositions completed during the years ended December 31, 2016 and 2015 : Properties Submarket Month of Disposition Gross Site Acreage (unaudited) Sales Price (1) (in millions) 2016 Land Dispositions Carlsbad Oaks - Lot 7 (2) Carlsbad January 7.6 $ 4.5 Carlsbad Oaks - Lots 4 & 5 Carlsbad June 11.2 6.0 Carlsbad Oaks - Lot 8 Carlsbad June 13.2 8.9 Total 2016 Land Dispositions (3)(4) 32.0 $ 19.4 2015 Land Disposition 17150 Von Karman (4) Irvine January 8.5 $ 26.0 __________________ (1) Represents gross sales price before the impact of commissions and closing costs. (2) This land parcel was classified as held for sale as of December 31, 2015. (3) In connection with these land dispositions, $2.3 million of secured debt was assumed by the buyers. (4) The 2016 land dispositions resulted in a net loss on sales of $0.3 million and the 2015 land disposition resulted in gain on sale of $17.3 million . Restricted Cash Related to Dispositions We did not have any restricted cash related to dispositions or Section 1031 Exchanges as of December 31, 2017 . As of December 31, 2016 approximately $48.4 million of net proceeds related to the land and operating property dispositions during the year ended December 31, 2016 was temporarily held at a qualified intermediary, at our direction, for the purpose of facilitating Section 1031 Exchanges. During January 2017, the Section 1031 Exchange was successfully completed and the cash proceeds were released from the qualified intermediary.

Deferred Leasing Costs and Acqu

Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, net	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, net	Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, net The following table summarizes our deferred leasing costs and acquisition-related intangible assets (acquired value of leasing costs, above-market operating leases, in-place leases and below-market ground lease obligation) and intangible liabilities (acquired value of below-market operating leases and above-market ground lease obligation) as of December 31, 2017 and 2016 : December 31, 2017 December 31, 2016 (in thousands) Deferred Leasing Costs and Acquisition-related Intangible Assets, net: Deferred leasing costs $ 248,598 $ 239,958 Accumulated amortization (101,917 ) (89,633 ) Deferred leasing costs, net 146,681 150,325 Above-market operating leases 4,199 10,304 Accumulated amortization (3,068 ) (6,933 ) Above-market operating leases, net 1,131 3,371 In-place leases 82,097 94,813 Accumulated amortization (46,625 ) (40,593 ) In-place leases, net 35,472 54,220 Below-market ground lease obligation 490 490 Accumulated amortization (46 ) (38 ) Below-market ground lease obligation, net 444 452 Total deferred leasing costs and acquisition-related intangible assets, net $ 183,728 $ 208,368 Acquisition-related Intangible Liabilities, net: (1) Below-market operating leases $ 65,440 $ 69,472 Accumulated amortization (40,495 ) (33,689 ) Below-market operating leases, net 24,945 35,783 Above-market ground lease obligation 6,320 6,320 Accumulated amortization (626 ) (525 ) Above-market ground lease obligation, net 5,694 5,795 Total acquisition-related intangible liabilities, net $ 30,639 $ 41,578 _______________ (1) Included in deferred revenue and acquisition-related intangible liabilities, net in the consolidated balance sheets. The following table sets forth amortization related to deferred leasing costs and acquisition-related intangibles for the years ended December 31, 2017 , 2016 and 2015 . Year Ended December 31, 2017 2016 2015 (in thousands) Deferred leasing costs (1) $ 31,675 $ 28,639 $ 27,866 Above-market operating leases (2) 2,240 1,509 2,532 In-place leases (1) 18,650 11,676 14,622 Below-market ground lease obligation (3) 8 8 8 Below-market operating leases (4) (10,768 ) (8,674 ) (10,980 ) Above-market ground lease obligation (5) (101 ) (101 ) (101 ) Total $ 41,704 $ 33,057 $ 33,947 _______________ (1) The amortization of deferred leasing costs and in-place leases is recorded to depreciation and amortization expense and the amortization of lease incentives is recorded as a reduction to rental income in the consolidated statements of operations for the periods presented. (2) The amortization of above-market operating leases is recorded as a decrease to rental income in the consolidated statements of operations for the periods presented. (3) The amortization of the below-market ground lease obligation is recorded as an increase to ground lease expense in the consolidated statements of operations for the periods presented. (4) The amortization of below-market operating leases is recorded as an increase to rental income in the consolidated statements of operations for the periods presented. (5) The amortization of the above-market ground lease obligation is recorded as a decrease to ground lease expense in the consolidated statements of operations for the periods presented. The following table sets forth the estimated annual amortization expense related to deferred leasing costs and acquisition-related intangibles as of December 31, 2017 for future periods: Year Deferred Leasing Costs Above-Market Operating Leases (1) In-Place Leases Below-Market Ground Lease Obligation (2) Below-Market Operating Leases (3) Above-Market Ground Lease Obligation (4) (in thousands) 2018 $ 30,033 $ 395 $ 13,286 $ 8 $ (9,456 ) $ (101 ) 2019 25,501 207 8,850 8 (6,854 ) (101 ) 2020 20,085 53 5,610 8 (3,942 ) (101 ) 2021 16,048 53 2,508 8 (1,253 ) (101 ) 2022 13,332 40 1,708 8 (790 ) (101 ) Thereafter 41,682 383 3,510 404 (2,650 ) (5,189 ) Total $ 146,681 $ 1,131 $ 35,472 $ 444 $ (24,945 ) $ (5,694 ) _______________ (1) Represents estimated annual amortization related to above-market operating leases. Amounts will be recorded as a decrease to rental income in the consolidated statements of operations. (2) Represents estimated annual amortization related to below-market ground lease obligations. Amounts will be recorded as an increase to ground lease expense in the consolidated statements of operations. (3) Represents estimated annual amortization related to below-market operating leases. Amounts will be recorded as an increase to rental income in the consolidated statements of operations. (4) Represents estimated annual amortization related to above-market ground lease obligations. Amounts will be recorded as a decrease to ground lease expense in the consolidated statements of operations.

Receivables

Receivables	12 Months Ended
	Dec. 31, 2017
Receivables [Abstract]
Receivables	Receivables Current Receivables, net Current receivables, net is primarily comprised of contractual rents and other lease-related obligations due from tenants. The balance consisted of the following as of December 31, 2017 and 2016 : December 31, 2017 December 31, 2016 (in thousands) Current receivables $ 19,235 $ 15,172 Allowance for uncollectible tenant receivables (2,309 ) (1,712 ) Current receivables, net $ 16,926 $ 13,460 Deferred Rent Receivables, net Deferred rent receivables, net consisted of the following as of December 31, 2017 and 2016 : December 31, 2017 December 31, 2016 (in thousands) Deferred rent receivables $ 249,629 $ 220,501 Allowance for deferred rent receivables (3,238 ) (1,524 ) Deferred rent receivables, net $ 246,391 $ 218,977

Prepaid Expenses and Other Asse

Prepaid Expenses and Other Assets, Net	12 Months Ended
	Dec. 31, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid Expenses and Other Assets, Net	Prepaid Expenses and Other Assets, Net Prepaid expenses and other assets, net consisted of the following at December 31, 2017 and 2016 : December 31, 2017 December 31, 2016 (in thousands) Furniture, fixtures and other long-lived assets, net $ 39,686 $ 40,395 Notes receivable (1) 19,912 19,439 Prepaid expenses & acquisition deposits 55,108 10,774 Total Prepaid Expenses and Other Assets, Net $ 114,706 $ 70,608 _______________ (1) Our notes receivables are held by two unrelated third parties. Approximately $15.1 million of our notes receivable balance was secured by real estate as of December 31, 2017 and 2016 .

Secured and Unsecured Debt of t

Secured and Unsecured Debt of the Company	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Secured and Unsecured Debt of the Company	Secured and Unsecured Debt of the Company In this Note 8, the “Company” refers solely to Kilroy Realty Corporation and not to any of our subsidiaries. The Company itself does not hold any indebtedness. All of our secured and unsecured debt is held directly by the Operating Partnership. The Company generally guarantees all the Operating Partnership’s unsecured debt obligations including the unsecured revolving credit facility, the $150.0 million unsecured term loan facility and all of the unsecured senior notes. At December 31, 2017 and 2016 , the Operating Partnership had $2.0 billion and $1.8 billion , respectively, outstanding in total, including unamortized discounts and deferred financing costs, under these unsecured debt obligations. In addition, although the remaining $0.3 billion and $0.5 billion of the Operating Partnership’s debt as of December 31, 2017 and 2016 , respectively, is secured and non-recourse to the Company, the Company provides limited customary secured debt guarantees for items such as voluntary bankruptcy, fraud, misapplication of payments and environmental liabilities. Debt Covenants and Restrictions One of the covenants contained within the unsecured revolving credit facility and the unsecured term loan facility as discussed further below in Note 9 prohibits the Company from paying dividends during an event of default in excess of an amount which results in distributions to us in an amount sufficient to permit us to pay dividends to our stockholders that we reasonably believe are necessary to (a) maintain our qualification as a REIT for federal and state income tax purposes and (b) avoid the payment of federal or state income or excise tax.

Secured and Unsecured Debt of22

Secured and Unsecured Debt of the Operating Partnership	12 Months Ended
	Dec. 31, 2017
Debt Instrument [Line Items]
Secured and Unsecured Debt of the Operating Partnership	Secured and Unsecured Debt of the Company In this Note 8, the “Company” refers solely to Kilroy Realty Corporation and not to any of our subsidiaries. The Company itself does not hold any indebtedness. All of our secured and unsecured debt is held directly by the Operating Partnership. The Company generally guarantees all the Operating Partnership’s unsecured debt obligations including the unsecured revolving credit facility, the $150.0 million unsecured term loan facility and all of the unsecured senior notes. At December 31, 2017 and 2016 , the Operating Partnership had $2.0 billion and $1.8 billion , respectively, outstanding in total, including unamortized discounts and deferred financing costs, under these unsecured debt obligations. In addition, although the remaining $0.3 billion and $0.5 billion of the Operating Partnership’s debt as of December 31, 2017 and 2016 , respectively, is secured and non-recourse to the Company, the Company provides limited customary secured debt guarantees for items such as voluntary bankruptcy, fraud, misapplication of payments and environmental liabilities. Debt Covenants and Restrictions One of the covenants contained within the unsecured revolving credit facility and the unsecured term loan facility as discussed further below in Note 9 prohibits the Company from paying dividends during an event of default in excess of an amount which results in distributions to us in an amount sufficient to permit us to pay dividends to our stockholders that we reasonably believe are necessary to (a) maintain our qualification as a REIT for federal and state income tax purposes and (b) avoid the payment of federal or state income or excise tax.
Kilroy Realty, L.P. [Member]
Debt Instrument [Line Items]
Secured and Unsecured Debt of the Operating Partnership	Secured and Unsecured Debt of the Operating Partnership Secured Debt The following table sets forth the composition of our secured debt as of December 31, 2017 and 2016 : Annual Stated Interest Rate (1) GAAP Effective Rate (1)(2) Maturity Date December 31, Type of Debt 2017 2016 (in thousands) Mortgage note payable 3.57% 3.57% December 2026 $ 170,000 $ 170,000 Mortgage note payable (3) 4.48% 4.48% July 2027 93,081 94,754 Mortgage note payable (3)(4) 6.05% 3.50% June 2019 78,894 82,443 Mortgage note payable (3)(5) 4.27% 4.27% February 2018 — 125,756 Mortgage note payable (6) 7.15% 7.15% May 2017 — 1,215 Total secured debt $ 341,975 $ 474,168 Unamortized Deferred Financing Costs (1,175 ) (1,396 ) Total secured debt, net $ 340,800 $ 472,772 ______________ (1) All interest rates presented are fixed-rate interest rates. (2) Represents the effective interest rate including the amortization of initial issuance discounts/premiums excluding the amortization of deferred financing costs. (3) The secured debt and the related properties that secure the debt are held in a special purpose entity and the properties are not available to satisfy the debts and other obligations of the Company or the Operating Partnership. (4) As of December 31, 2017 and 2016 , the mortgage loan had unamortized debt premiums of $2.6 million and $4.4 million , respectively. (5) This mortgage note payable, held by a consolidated property partnership, was repaid in November 2017 at par. NBREM contributed $54.4 million to fund their proportionate share of the payoff. Refer to Note 11 “Noncontrolling Interests on Company’s Consolidated Financial Statements” for additional information. (6) This mortgage note payable was repaid in February 2017 at par. The Operating Partnership’s secured debt was collateralized by operating properties with a combined net book value of approximately $338.2 million as of December 31, 2017 . Although our mortgage loans are secured and non-recourse to the Company and the Operating Partnership, the Company provides limited customary secured debt guarantees for items such as voluntary bankruptcy, fraud, misapplication of payments and environmental liabilities. As of December 31, 2017 , all of the Operating Partnership’s secured loans contained restrictions that would require the payment of prepayment penalties for the acceleration of outstanding debt. The mortgage notes payable are secured by deeds of trust on certain of our properties and the assignment of certain rents and leases associated with those properties. Unsecured Senior Notes The following table summarizes the balance and significant terms of the registered unsecured senior notes issued by the Operating Partnership and outstanding, which are presented net of unamortized discounts of $6.3 million and $6.6 million , as of December 31, 2017 and 2016 , respectively: Net Carrying Amount Issuance date Maturity date Stated coupon rate Effective interest rate (1) 2017 2016 (in thousands) 3.450% Unsecured Senior Notes (2) December 2017 December 2024 3.450% 3.471% $ 425,000 $ — Unamortized discount and deferred financing costs (4,047 ) — Net carrying amount $ 420,953 $ — 3.450% Unsecured Senior Notes (3) February 2017 February 2029 3.450% 3.450% $ 75,000 $ — Unamortized discount and deferred financing costs (475 ) — Net carrying amount $ 74,525 $ — 3.350% Unsecured Senior Notes (3) February 2017 February 2027 3.350% 3.350% $ 175,000 $ — Unamortized discount and deferred financing costs (1,056 ) — Net carrying amount $ 173,944 $ — 4.375% Unsecured Senior Notes (4) September 2015 October 2025 4.375% 4.444% $ 400,000 $ 400,000 Unamortized discount and deferred financing costs (4,292 ) (4,846 ) Net carrying amount $ 395,708 $ 395,154 4.250% Unsecured Senior Notes (5) July 2014 August 2029 4.250% 4.352% $ 400,000 $ 400,000 Unamortized discount and deferred financing costs (6,164 ) (6,696 ) Net carrying amount $ 393,836 $ 393,304 3.800% Unsecured Senior Notes (6) January 2013 January 2023 3.800% 3.804% $ 300,000 $ 300,000 Unamortized discount and deferred financing costs (1,382 ) (1,656 ) Net carrying amount $ 298,618 $ 298,344 4.800% Unsecured Senior Notes (6)(7) July 2011 July 2018 4.800% 4.827% $ — $ 325,000 Unamortized discount and deferred financing costs — (767 ) Net carrying amount $ — $ 324,233 6.625% Unsecured Senior Notes (8) May 2010 June 2020 6.625% 6.744% $ 250,000 $ 250,000 Unamortized discount and deferred financing costs (1,321 ) (1,868 ) Net carrying amount $ 248,679 $ 248,132 Total Unsecured Senior Notes, Net $ 2,006,263 $ 1,659,167 ________________________ (1) Represents the effective interest rate including the amortization of initial issuance discounts, excluding the amortization of deferred financing costs. (2) Interest on these notes is payable semi-annually in arrears on June 15th and December 15th of each year. (3) Interest on these notes is payable semi-annually in arrears on February 17th and August 17th of each year. (4) Interest on these notes is payable semi-annually in arrears on April 1st and October 1st of each year. (5) Interest on these notes is payable semi-annually in arrears on February 15th and August 15th of each year. (6) Interest on these notes is payable semi-annually in arrears on January 15th and July 15th of each year. (7) Certain common limited partners in the Operating Partnership that previously contributed their interests in the property at 6255 W. Sunset Blvd., Los Angeles, California to the Operating Partnership entered into an agreement with the Company. Pursuant to this agreement, such common limited partners will reimburse the Company for a portion of any amounts the Company may be required to pay pursuant to its guarantee of the Operating Partnership's 4.800% Senior Notes due 2018 or that the Company may otherwise become required to pay under applicable law with respect to such notes. These notes were redeemed by the Company in December 2017. (8) Interest on these notes is payable semi-annually in arrears on June 1st and December 1st of each year. Unsecured Senior Notes - Registered Offerings In December 2017, the Operating Partnership issued $425.0 million of aggregate principal amount of unsecured senior notes in a registered public offering, as shown on the table above. The outstanding balance of the unsecured senior notes is included in unsecured debt, net of initial issuance discount of $0.6 million , on our consolidated balance sheet. The unsecured senior notes, which are scheduled to mature on December 15, 2024 , require semi-annual interest payments each June and December based on a stated annual interest rate of 3.450% . The Operating Partnership may redeem the notes at any time prior to September 15, 2024, either in whole or in part, subject to the payment of an early redemption premium. In December 2017, we used a portion of the net proceeds from the issuance of our $425.0 million , 3.450% unsecured senior notes to early redeem, at our option, the $325.0 million aggregate principal amount of our outstanding 4.800% unsecured senior notes that were scheduled to mature on July 15, 2018 , as shown on the table above. In connection with our early redemption, we incurred a $5.3 million loss on early extinguishment of debt comprised of $5.0 million premium paid to the note holders at the redemption date and $0.3 million write-off of the unamortized discount and deferred financing costs. Unsecured Senior Notes - Private Placement On September 14, 2016, the Operating Partnership entered into a Note Purchase Agreement in a private placement (the “Note Purchase Agreement”), in connection with the issuance and sale of $175.0 million principal amount of the Operating Partnership’s 3.35% Senior Notes, Series A, due February 17, 2027 (the “Series A Notes”), and $75.0 million principal amount of the Operating Partnership’s 3.45% Senior Notes, Series B, due February 17, 2029 (the “Series B Notes” and, together with the Series A Notes, the “Series A and B Notes”), as shown on the table above. Under the delayed draw option of the Series A and B Notes, the Operating Partnership was required to issue $175.0 million principal amount of its Series A Notes and $75.0 million principal amount of its Series B Notes by February 17, 2017. On February 17, 2017, the Operating Partnership issued the $175.0 million principal amount of its Series A Notes and the $75.0 million principal amount of its Series B Notes. The Series A Notes mature on February 17, 2027 , and the Series B Notes mature on February 17, 2029 , in each case unless earlier redeemed or prepaid pursuant to the terms of the Note Purchase Agreement. Interest on the Series A and B Notes is payable semi-annually in arrears on February 17 and August 17 of each year. As of December 31, 2017 , there was $175.0 million and $75.0 million issued and outstanding aggregate principal amount of Series A and B Notes, respectively. The Operating Partnership may, at its option and upon notice to the purchasers of the Series A and B Notes, prepay at any time all, or from time to time any part of the Series A and B Notes then outstanding (in an amount not less than 5% of the aggregate principal amount of the Series A and B Notes then outstanding in the case of a partial prepayment), at 100% of the principal amount so prepaid, plus the make-whole amount determined for the prepayment date with respect to such principal amount as set forth in the Note Purchase Agreement. In connection with the issuance of the Series A and B Notes, the Company entered into a guaranty agreement whereby it guarantees the payment by the Operating Partnership of all amounts due with respect to the Series A and B Notes and the performance by the Operating Partnership of its obligations under the Note Purchase Agreement. Unsecured Revolving Credit Facility and Term Loan Facility In July 2017, the Operating Partnership amended and restated the terms of its unsecured revolving credit facility and unsecured term loan facility (together, the “Facility”). The amendment and restatement increased the size of the unsecured revolving credit facility from $600.0 million to $750.0 million , maintained the size of the unsecured term loan facility of $150.0 million , reduced the borrowing costs and extended the maturity date of the Facility to July 2022. The unsecured term loan facility features a 12-month delayed draw option (subject to a specified reduction in commitments unless 50% drawn within six months). The following table summarizes the balance and terms of our unsecured revolving credit facility as of December 31, 2017 and 2016 : December 31, 2017 December 31, 2016 (in thousands) Outstanding borrowings $ — $ — Remaining borrowing capacity 750,000 600,000 Total borrowing capacity (1) $ 750,000 $ 600,000 Interest rate (2) 2.56 % 1.82 % Facility fee-annual rate (3) 0.200% Maturity date July 2022 July 2019 _______________ (1) As of December 31, 2017 , 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. As of December 31, 2016 , we had the option to borrow, subject to bank approval and obtaining commitments for any additional borrowing capacity, up to an additional $311.0 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% and LIBOR plus 1.050% as of December 31, 2017 and December 31, 2016 , respectively. (3) Our facility fee is paid on a quarterly basis and is calculated based on the total borrowing capacity. In addition to the facility fee, we incurred debt origination and legal costs. As of December 31, 2017 and 2016 , $6.0 million and $3.3 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 respective 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. The following table summarizes the balance and terms of our unsecured term loan facility as of December 31, 2017 and 2016 : December 31, 2017 December 31, 2016 (in thousands) Outstanding borrowings (1) $ — $ 150,000 Remaining borrowing capacity 150,000 — Total borrowing capacity (2) $ 150,000 $ 150,000 Interest rate (3) 2.66 % 1.85 % Undrawn facility fee-annual rate (4) 0.200 % — % Maturity date July 2022 July 2019 _______________ (1) In July 2017, the unsecured term loan facility was paid down and the Facility was amended to include a 12-month delayed draw option (subject to a specified reduction in commitments unless 50% drawn within six months) on the unsecured term loan facility. The Company may draw on the unsecured term loan facility through July 2018, at which time the outstanding balance will become the balance of the unsecured term loan facility and no additional draws may be made. In January 2018, the Company borrowed $75.0 million under the unsecured term loan facility. (2) As of December 31, 2017 and December 31, 2016 , $1.2 million and $0.7 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% and LIBOR plus 1.150% as of December 31, 2017 and December 31, 2016 , respectively. (4) In July 2017, the Facility was amended to include a facility fee on the remaining borrowing capacity of the unsecured term loan facility, which is paid on a monthly basis. As of December 31, 2016 the Operating Partnership had a $39.0 million unsecured term loan outstanding with an annual interest rate of LIBOR plus 1.150% that was to mature in July 2019. Concurrently with the amendment of the Facility, the Operating Partnership repaid its $39.0 million unsecured term loan. As of December 31, 2016 , there was $0.2 million of unamortized deferred financing costs on the unsecured term loan. Debt Covenants and Restrictions The unsecured revolving credit facility, the unsecured term loan facility, the unsecured senior notes, the Series A and B 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 December 31, 2017 and 2016 . Debt Maturities The following table summarizes the stated debt maturities and scheduled amortization payments as of December 31, 2017 : Year (in thousands) 2018 $ 3,584 2019 76,309 2020 255,137 2021 5,342 2022 5,554 Thereafter 2,018,469 Total aggregate principal value (1) $ 2,364,395 ________________________ (1) Includes gross principal balance of outstanding debt before the effect of the following at December 31, 2017 : $13.6 million of unamortized deferred financing costs for the unsecured senior notes and secured debt, $6.3 million of unamortized discounts for the unsecured senior notes and $2.6 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 years ended December 31, 2017 , 2016 and 2015 . The interest expense capitalized was recorded as a cost of development and increased the carrying value of undeveloped land and construction in progress. Year Ended December 31, 2017 2016 2015 (in thousands) Gross interest expense $ 112,577 $ 105,263 $ 109,647 Capitalized interest and deferred financing costs (46,537 ) (49,460 ) (51,965 ) Interest expense $ 66,040 $ 55,803 $ 57,682

Deferred Revenue and Acquisitio

Deferred Revenue and Acquisition Related Liabilities, net	12 Months Ended
	Dec. 31, 2017
Deferred Revenue Disclosure [Abstract]
Deferred Revenue and Acquisition Related Liabilities, net	Deferred Revenue and Acquisition Related Liabilities, net Deferred revenue and acquisition-related liabilities, net consisted of the following at December 31, 2017 and 2016 : December 31, 2017 2016 (in thousands) Deferred revenue related to tenant-funded tenant improvements $ 104,260 $ 99,489 Other deferred revenue 10,991 9,293 Acquisition-related intangible liabilities, net (1) 30,639 41,578 Total $ 145,890 $ 150,360 ________________________ (1) See Note 5 “Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, net” for additional information regarding our acquisition-related intangible liabilities. Deferred Revenue Related to Tenant-funded Tenant Improvements During the years ended December 31, 2017 , 2016 , and 2015 , $16.8 million , $13.2 million and $13.3 million , respectively, of deferred revenue related to tenant-funded tenant improvements was amortized and recognized as rental income. The following is the estimated amortization of deferred revenue related to tenant-funded tenant improvements as of December 31, 2017 for the next five years and thereafter: Year Ending (in thousands) 2018 $ 16,644 2019 14,851 2020 14,062 2021 12,607 2022 11,458 Thereafter 34,638 Total $ 104,260

Noncontrolling Interests on the

Noncontrolling Interests on the Company's Consolidated Financial Statements	12 Months Ended
	Dec. 31, 2017
Noncontrolling Interest [Abstract]
Noncontrolling Interests on the Company's Consolidated Financial Statements	Noncontrolling Interests on the Company’s Consolidated Financial Statements Common Units of the Operating Partnership The Company owned a 97.9% and 97.5% common general partnership interest in the Operating Partnership as of December 31, 2017 and 2016 , respectively. The remaining 2.1% and 2.5% common limited partnership interest as of December 31, 2017 and 2016 , respectively, was owned by non-affiliated investors and certain of our executive officers and directors in the form of noncontrolling common units. There were 2,077,193 and 2,381,543 common units outstanding held by these investors, executive officers and directors as of December 31, 2017 and 2016 , respectively. The decrease in the common units from December 31, 2016 to December 31, 2017 was attributable to 304,350 common unit redemptions. The noncontrolling common units may be redeemed by unitholders for cash. Except under certain circumstances, we, at our option, may satisfy the cash redemption obligation with shares of the Company’s common stock on a one-for-one basis. If satisfied in cash, the value for each noncontrolling common unit upon redemption is the amount equal to the average of the closing quoted price per share of the Company’s common stock, par value $0.01 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 $154.5 million and $174.9 million as of December 31, 2017 and 2016 , respectively. This redemption value does not necessarily represent the amount that would be distributed with respect to each noncontrolling common unit in the event of our termination or liquidation. In the event of our termination or liquidation, it is expected in most cases that each common unit would be entitled to a liquidating distribution equal to the liquidating distribution payable in respect of each share of the Company’s common stock. Noncontrolling Interest in Consolidated Property Partnerships On August 30, 2016, the Operating Partnership entered into agreements with Norges Bank Real Estate Management (“NBREM”) whereby NBREM invested, through two REIT subsidiaries, in two existing companies that owned the Company’s 100 First Street and 303 Second Street office properties located in San Francisco, California. Based on a gross valuation of the two properties of approximately $1.2 billion , NBREM contributed a total of $452.9 million , for a 44% common equity interest in the companies, which was net of approximately $55.3 million of its proportionate share of the existing mortgage debt on 303 Second Street as of the transaction date. In November 2017, NBREM contributed $54.4 million to fund their proportionate share of the Company’s repayment of this mortgage debt. The transaction was structured with a staggered closing. On August 30, 2016, the first tranche of the transaction closed and NBREM contributed $191.4 million plus a working capital contribution of $2.1 million for a 44% common ownership interest in 100 First LLC. On November 30, 2016, the second tranche of the transaction closed and NBREM contributed $261.5 million , which was net of its proportionate share of the existing mortgage debt secured by the 303 Second Street property of approximately $55.3 million , plus a working capital contribution of $2.9 million for a 44% common ownership interest in 303 Second LLC. The transactions did not meet the criteria to qualify as sales of real estate because the Company continues to effectively control the properties and therefore continued to account for the 100 First Street and 303 Second Street office properties on a consolidated basis in its financial statements. At formation, the Company accounted for the transactions as equity transactions and recognized noncontrolling interests in its consolidated balance sheets totaling approximately $124.5 million , which was equal to 44% of the aggregate net asset value of 100 First LLC and 303 Second LLC immediately prior to the transactions (which was net of NBREM’s 44% share of the existing mortgage debt of $55.3 million ) plus an additional $5.0 million working capital contribution made by NBREM. The amount of NBREM’s total contribution not recognized as noncontrolling interest, net of transaction costs, was approximately $329.0 million . This amount was not reflected as a gain on sale of operating properties in the Company’s consolidated statements of operations and instead was reflected as an increase in additional paid-in capital and partners’ capital in the Company’s and the Operating Partnership’s consolidated balance sheets, respectively. Transfers of less than 50% of an entity ownership interest are normally not subject to certain tax assessments in California and therefore the Company believes that the two tranches of the transaction do not meet the statutory requirements for such tax assessments. If the taxing authority attempted to assess such tax assessments on the transactions, the Company estimates it could incur additional taxes of up to $10.9 million and $18.0 million for the first and second tranches of the transaction, respectively, plus potential penalties and interest. In connection with the transaction, the Company provides customary property management, leasing and construction management services for both properties. 100 First Street is a 467,095 square foot office tower, and 303 Second Street is a 740,047 square foot office property, both located in the South of Market submarket in San Francisco, California. The noncontrolling interests in 100 First LLC and 303 Second LLC as of December 31, 2017 and 2016 were $175.4 million and $124.3 million , respectively, which is recognized in noncontrolling interests in consolidated property partnerships on the Company’s consolidated balance sheets. The remaining amount of noncontrolling interests in consolidated property partnerships represents the third party equity interest in Redwood LLC. This noncontrolling interest was $6.2 million and $6.4 million as of December 31, 2017 and 2016 , respectively. Noncontrolling Interests on the Operating Partnership’s Consolidated Financial Statements Consolidated Property Partnerships On August 30, 2016, the Operating Partnership entered into agreements with NBREM whereby NBREM invested, through two REIT subsidiaries, in two existing companies that owned the Company’s 100 First Street and 303 Second Street office properties located in San Francisco, California. Based on a gross valuation of the two properties of approximately $1.2 billion , NBREM contributed a total of $452.9 million for a 44% common equity interest in the companies, which is net of approximately $55.3 million of its proportionate share of the existing mortgage debt. In November 2017, the Company repaid the mortgage debt secured by the 303 Second Street office property. Prior to the repayment, NBREM contributed $54.4 million to fund their proportionate share of the repayment. Refer to Note 11 for additional information regarding these transactions.

Noncontrolling Interests on t25

Noncontrolling Interests on the Operating Partnership's Consolidated Financial Statements	12 Months Ended
	Dec. 31, 2017
Noncontrolling Interest [Abstract]
Noncontrolling Interests on the Operating Partnership’s Consolidated Financial Statements	Noncontrolling Interests on the Company’s Consolidated Financial Statements Common Units of the Operating Partnership The Company owned a 97.9% and 97.5% common general partnership interest in the Operating Partnership as of December 31, 2017 and 2016 , respectively. The remaining 2.1% and 2.5% common limited partnership interest as of December 31, 2017 and 2016 , respectively, was owned by non-affiliated investors and certain of our executive officers and directors in the form of noncontrolling common units. There were 2,077,193 and 2,381,543 common units outstanding held by these investors, executive officers and directors as of December 31, 2017 and 2016 , respectively. The decrease in the common units from December 31, 2016 to December 31, 2017 was attributable to 304,350 common unit redemptions. The noncontrolling common units may be redeemed by unitholders for cash. Except under certain circumstances, we, at our option, may satisfy the cash redemption obligation with shares of the Company’s common stock on a one-for-one basis. If satisfied in cash, the value for each noncontrolling common unit upon redemption is the amount equal to the average of the closing quoted price per share of the Company’s common stock, par value $0.01 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 $154.5 million and $174.9 million as of December 31, 2017 and 2016 , respectively. This redemption value does not necessarily represent the amount that would be distributed with respect to each noncontrolling common unit in the event of our termination or liquidation. In the event of our termination or liquidation, it is expected in most cases that each common unit would be entitled to a liquidating distribution equal to the liquidating distribution payable in respect of each share of the Company’s common stock. Noncontrolling Interest in Consolidated Property Partnerships On August 30, 2016, the Operating Partnership entered into agreements with Norges Bank Real Estate Management (“NBREM”) whereby NBREM invested, through two REIT subsidiaries, in two existing companies that owned the Company’s 100 First Street and 303 Second Street office properties located in San Francisco, California. Based on a gross valuation of the two properties of approximately $1.2 billion , NBREM contributed a total of $452.9 million , for a 44% common equity interest in the companies, which was net of approximately $55.3 million of its proportionate share of the existing mortgage debt on 303 Second Street as of the transaction date. In November 2017, NBREM contributed $54.4 million to fund their proportionate share of the Company’s repayment of this mortgage debt. The transaction was structured with a staggered closing. On August 30, 2016, the first tranche of the transaction closed and NBREM contributed $191.4 million plus a working capital contribution of $2.1 million for a 44% common ownership interest in 100 First LLC. On November 30, 2016, the second tranche of the transaction closed and NBREM contributed $261.5 million , which was net of its proportionate share of the existing mortgage debt secured by the 303 Second Street property of approximately $55.3 million , plus a working capital contribution of $2.9 million for a 44% common ownership interest in 303 Second LLC. The transactions did not meet the criteria to qualify as sales of real estate because the Company continues to effectively control the properties and therefore continued to account for the 100 First Street and 303 Second Street office properties on a consolidated basis in its financial statements. At formation, the Company accounted for the transactions as equity transactions and recognized noncontrolling interests in its consolidated balance sheets totaling approximately $124.5 million , which was equal to 44% of the aggregate net asset value of 100 First LLC and 303 Second LLC immediately prior to the transactions (which was net of NBREM’s 44% share of the existing mortgage debt of $55.3 million ) plus an additional $5.0 million working capital contribution made by NBREM. The amount of NBREM’s total contribution not recognized as noncontrolling interest, net of transaction costs, was approximately $329.0 million . This amount was not reflected as a gain on sale of operating properties in the Company’s consolidated statements of operations and instead was reflected as an increase in additional paid-in capital and partners’ capital in the Company’s and the Operating Partnership’s consolidated balance sheets, respectively. Transfers of less than 50% of an entity ownership interest are normally not subject to certain tax assessments in California and therefore the Company believes that the two tranches of the transaction do not meet the statutory requirements for such tax assessments. If the taxing authority attempted to assess such tax assessments on the transactions, the Company estimates it could incur additional taxes of up to $10.9 million and $18.0 million for the first and second tranches of the transaction, respectively, plus potential penalties and interest. In connection with the transaction, the Company provides customary property management, leasing and construction management services for both properties. 100 First Street is a 467,095 square foot office tower, and 303 Second Street is a 740,047 square foot office property, both located in the South of Market submarket in San Francisco, California. The noncontrolling interests in 100 First LLC and 303 Second LLC as of December 31, 2017 and 2016 were $175.4 million and $124.3 million , respectively, which is recognized in noncontrolling interests in consolidated property partnerships on the Company’s consolidated balance sheets. The remaining amount of noncontrolling interests in consolidated property partnerships represents the third party equity interest in Redwood LLC. This noncontrolling interest was $6.2 million and $6.4 million as of December 31, 2017 and 2016 , respectively. Noncontrolling Interests on the Operating Partnership’s Consolidated Financial Statements Consolidated Property Partnerships On August 30, 2016, the Operating Partnership entered into agreements with NBREM whereby NBREM invested, through two REIT subsidiaries, in two existing companies that owned the Company’s 100 First Street and 303 Second Street office properties located in San Francisco, California. Based on a gross valuation of the two properties of approximately $1.2 billion , NBREM contributed a total of $452.9 million for a 44% common equity interest in the companies, which is net of approximately $55.3 million of its proportionate share of the existing mortgage debt. In November 2017, the Company repaid the mortgage debt secured by the 303 Second Street office property. Prior to the repayment, NBREM contributed $54.4 million to fund their proportionate share of the repayment. Refer to Note 11 for additional information regarding these transactions.

Stockholders' Equity of the Com

Stockholders' Equity of the Company	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Stockholders' Equity of the Company	Stockholders’ Equity of the Company Preferred Stock On August 15, 2017 , the Company redeemed all 4,000,000 shares of its 6.375% Series H Cumulative Redeemable Preferred Stock (“Series H Preferred Stock”). The shares of Series H Preferred Stock were redeemed at a redemption price equal to their stated liquidation preference of $25.00 per share, representing $100.0 million in aggregate. The redemption payment did not include any additional accrued dividends because the redemption date was also the dividend payment date. On March 30, 2017 (the “Series G Redemption Date”), the Company redeemed all 4,000,000 shares of its 6.875% Series G Cumulative Redeemable Preferred Stock (“Series G Preferred Stock”). The shares of Series G Preferred Stock were redeemed at a redemption price equal to their stated liquidation preference of $25.00 per share, representing $100.0 million in aggregate, plus all accrued and unpaid dividends to the Series G Redemption Date. In connection with the redemption of the Series G and Series H Preferred Stock, during the year ended December 31, 2017 we recorded non-cash charges of $7.6 million as a reduction to net income available to common stockholders for the original issuance costs of the Series H and Series G Preferred Stock. Common Stock Common Stock Issuances In January 2017, the Company completed an underwritten public offering of 4,427,500 shares of its common stock. The net offering proceeds, after deducting underwriting discounts and offering expenses, were approximately $308.8 million . We used a portion of the proceeds to partially fund our $1.90 per share of special dividends declared by our Board of Directors in December 2016 and used the remaining proceeds for general corporate uses, to fund development expenditures and to repay outstanding indebtedness. In July 2015, the Company completed the sale and issuance of 3,733,766 shares of its common stock at a price of $66.19 per share for aggregate gross proceeds of $249.8 million and aggregate net proceeds after offering costs of $249.6 million through a registered direct placement with an institutional investor. 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. Since commencement of the program through December 31, 2017 , we have sold 2,694,242 shares of common stock having an aggregate gross sales price of $200.1 million . As of December 31, 2017 , 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. The following table sets forth information regarding sales of our common stock under our at-the-market offering programs for the years ended December 31, 2017 , 2016 and 2015 : Year Ended December 31, 2017 2016 2015 (in millions, except share data) Shares of common stock sold during the period 235,077 451,398 1,866,267 Aggregate gross proceeds $ 17.7 $ 32.3 $ 140.1 Aggregate net proceeds after selling commissions $ 17.5 $ 31.9 $ 138.2 The proceeds from sales were used to fund acquisitions, development expenditures and general corporate purposes including repayment of borrowings under the unsecured revolving credit facility. Common Stock Repurchases On February 23, 2016, the Company’s Board of Directors approved a 4,000,000 share increase to the Company’s existing share repurchase program bringing the total current repurchase authorization to 4,988,025 shares. The Company did not repurchase shares of common stock under this program during the years ended December 31, 2017 or December 31, 2015 . In March 2016, the Company repurchased 52,199 shares of common stock at a weighted average price of $55.45 per share of common stock for $2.9 million . As of December 31, 2017 , 4,935,826 shares remain eligible for repurchase under the Company’s share repurchase program. Accrued Dividends and Distributions The following tables summarize accrued dividends and distributions for the noted outstanding shares of common stock, preferred stock, and noncontrolling units as of December 31, 2017 and 2016 : December 31, 2017 2016 (1) (in thousands) Dividends and Distributions payable to: Common stockholders $ 41,914 $ 212,074 Noncontrolling common unitholders of the Operating Partnership 883 5,418 RSU holders (2) 651 3,158 Total accrued dividends and distribution to common stockholders and noncontrolling unitholders 43,448 220,650 Preferred stockholders (3) — 1,656 Total accrued dividends and distributions $ 43,448 $ 222,306 ______________________ (1) Dividends and distributions payable to common stockholders, noncontrolling common unitholders of the Operating Partnership and RSU holders in 2016 include a special cash dividend of $1.90 per share that was declared by the Company’s Board of Directors on December 13, 2016. On January 13, 2017, the Company paid $184.3 million of special cash dividends to stockholders of record on December 30, 2016. This special dividend payment was in addition to the $36.4 million of regular dividends also paid on January 13, 2017 to common stockholders, unitholders and RSU holders of record on December 30, 2016. (2) The amount includes the value of the dividend equivalents that will be paid with additional RSUs (see Note 15 “Share-Based Compensation” for additional information). (3) The Series G and Series H Preferred stock were redeemed in March 2017 and August 2017, respectively, and the Company did not have any preferred stock outstanding as of December 31, 2017 . December 31, 2017 2016 Outstanding Shares and Units: Common stock (1) 98,620,333 93,219,439 Noncontrolling common units 2,077,193 2,381,543 RSUs (2) 1,488,724 1,395,189 Series G Preferred stock (3) — 4,000,000 Series H Preferred stock (3) — 4,000,000 ______________________ (1) The amount includes nonvested shares. (2) The amount includes nonvested RSUs. Does not include 665,110 and 659,051 market measure-based RSUs because not all the necessary performance conditions have been met as of December 31, 2017 and 2016 , respectively. Refer to Note 15 “Share-Based Compensation” for additional information. (3) The Series G and Series H Preferred stock were redeemed in March 2017 and August 2017, respectively.

Partners' Capital of the Operat

Partners' Capital of the Operating Partnership	12 Months Ended
	Dec. 31, 2017
Partners' Capital [Abstract]
Partners' Capital of the Operating Partnership	Partners' Capital of the Operating Partnership Preferred Units On August 15, 2017 , the Company redeemed all 4,000,000 shares of its 6.375% Series H Preferred Stock. For each share of Series H Preferred Stock that was outstanding, the Company had an equivalent number of 6.375% Series H Preferred Units (“Series H Preferred Units”) outstanding with substantially similar terms as the Series H Preferred Stock. In connection with the redemption of the Series H Preferred Stock, the Series H Preferred Units held by the Company were redeemed by the Operating Partnership. On March 30, 2017 , the Company redeemed all 4,000,000 shares of its 6.875% Series G Preferred Stock. For each share of Series G Preferred Stock that was outstanding, the Company had an equivalent number of 6.875% Series G Preferred Units (“Series G Preferred Units”) outstanding with substantially similar terms as the Series G Preferred Stock. In connection with the redemption of the Series G Preferred Stock, the Series G Preferred Units held by the Company were redeemed by the Operating Partnership. In connection with the redemption of the Series G and Series H Preferred Stock, during the year ended December 31, 2017 we recorded non-cash charges of $7.6 million as a reduction to net income available to common unitholders for the original issuance costs of the Series H and Series G Preferred Stock. Common Units Issuance of Common Units In January 2017, the Company completed an underwritten public offering of 4,427,500 shares of its common stock (see Note 13 “Stockholders’ Equity of the Company”). The net offering proceeds of approximately $308.8 million were contributed by the Company to the Operating Partnership in exchange for 4,427,500 common units. In March 2016, the Operating Partnership issued 867,701 common units in connection with a development acquisition (see Note 3 “Acquisitions”). Each common unit was valued at $55.36 , which was based on a trailing ten-day average of the closing quoted price per share of the Company’s common stock, par value $.01 per share, as reported on the NYSE, as calculated in accordance with the Partnership Agreement. In July 2015, the Company completed the sale and issuance of 3,733,766 shares of its common stock at a price of $66.19 per share for aggregate gross proceeds of $249.8 million and aggregate net proceeds after offering costs of $249.6 million through a registered direct placement with an institutional investor (see Note 13 “Stockholders’ Equity of the Company” for additional information). The net offering proceeds were contributed by the Company to the Operating Partnership in exchange for 3,733,766 common units. At-The-Market Stock Offering Program During the years ended December 31, 2017 , 2016 and 2015 , the Company utilized its at-the-market stock offering programs to issue shares of common stock (see Note 13 “Stockholders’ Equity of the Company” for additional information). The net offering proceeds and property acquired using net offering proceeds were contributed by the Company to the Operating Partnership in exchange for common units for the years ended December 31, 2017 , 2016 and 2015 are as follows: Year Ended December 31, 2017 2016 2015 (in millions, except share and per share data) Shares of common stock contributed by the Company 235,077 451,398 1,866,267 Common units exchanged for shares of common stock by the Company 235,077 451,398 1,866,267 Aggregate gross proceeds $ 17.7 $ 32.3 $ 140.1 Aggregate net proceeds after selling commissions $ 17.5 $ 31.9 $ 138.2 Common Units Outstanding The following table sets forth the number of common units held by the Company and the number of common units held by non-affiliated investors and certain of our executive officers and directors in the form of noncontrolling common units as well as the ownership interest held on each respective date: December 31, 2017 December 31, 2016 Company owned common units in the Operating Partnership 98,620,333 93,219,439 Company owned general partnership interest 97.9 % 97.5 % Noncontrolling common units of the Operating Partnership 2,077,193 2,381,543 Ownership interest of noncontrolling interest 2.1 % 2.5 % For a further discussion of the noncontrolling common units during the years ended December 31, 2017 and 2016 , refer to Note 11 “Noncontrolling Interests on the Company’s Consolidated Financial Statements.” Accrued Distributions The following tables summarize accrued distributions for the noted common and preferred units as of December 31, 2017 and 2016 : December 31, 2017 December 31, 2016 (1) (in thousands) Distributions payable to: General partner $ 41,914 $ 212,074 Common limited partners 883 5,418 RSU holders (2) 651 3,158 Total accrued distributions to common unitholders 43,448 220,650 Preferred unitholders (3) — 1,656 Total accrued distributions $ 43,448 $ 222,306 ______________________ (1) Distributions payable to the general partner, noncontrolling common unitholders of the Operating Partnership and RSU holders in 2016 include a special cash dividend of $1.90 per share that was declared by the Company’s Board of Directors on December 13, 2016. On January 13, 2017, the Company paid $184.3 million of special cash dividends to unitholders of record on December 30, 2016. This special dividend payment was in addition to the $36.4 million of regular dividends also paid on January 13, 2017 to common stockholders, unitholders and RSU holders of record on December 30, 2016. (2) The amount includes the value of the dividend equivalents that will be paid with additional RSUs (see Note 15 “Share-Based Compensation” for additional information). (3) The Series G and Series H Preferred units were redeemed in March 2017 and August 2017, respectively, and the Company did not have any preferred stock outstanding at December 31, 2017. December 31, 2017 December 31, 2016 Outstanding Units: Common units held by the general partner 98,620,333 93,219,439 Common units held by the limited partners 2,077,193 2,381,543 RSUs (1) 1,488,724 1,395,189 Series G Preferred units (2) — 4,000,000 Series H Preferred units (2) — 4,000,000 ______________________ (1) Does not include 665,110 and 659,051 market measure-based RSUs because not all the necessary performance conditions have been met as of December 31, 2017 and 2016 , respectively. Refer to Note 15 “Share-Based Compensation” for additional information. (2) The Series G and Series H Preferred units were redeemed in March 2017 and August 2017, respectively.

Share-Based Compensation

Share-Based Compensation	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation	Share-Based Compensation Stockholder Approved Share-Based Incentive Compensation Plan As of December 31, 2017 , we maintained one share-based incentive compensation plan, the Kilroy Realty 2006 Incentive Award Plan, as amended (the “2006 Plan”). The Company has a currently effective registration statement registering 9.2 million shares of our common stock for possible issuance under our 2006 Incentive Award Plan. As of December 31, 2017 , approximately 1.9 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 other performance and market conditions (as defined below) for awards still in a performance period. The Executive Compensation Committee ( the “Compensation Committee”) of the Company's Board of Directors may grant the following share-based awards to eligible individuals, as provided under the 2006 Plan: incentive stock options, nonqualified stock options, restricted stock (nonvested shares), stock appreciation rights, performance shares, performance stock units, dividend equivalents, stock payments, deferred stock, restricted stock units (“RSUs”), profit interest units, performance bonus awards, performance-based awards and other incentive awards. For each award granted under our share-based incentive compensation programs, the Operating Partnership simultaneously issues to the Company a number of common units equal to the number of shares of common stock ultimately paid by the Company in respect of such awards. Stock Award Deferral Program We have a Stock Award Deferral Program (the “RSU Program”) under the 2006 Plan. Under the RSU Program, participants may defer receipt of awards of nonvested shares that may be granted by electing to receive an equivalent number of RSUs in lieu of such nonvested shares, or defer payment of RSU awards. Each RSU represents the right to receive one share of our common stock in the future and is subject to the same vesting conditions that would have applied if the award had been issued in nonvested shares. RSUs carry with them the right to receive dividend equivalents such that participants receive additional RSUs at the time dividends are paid equal to the value of the dividend earned on the shares underlying the participant’s RSUs. The dividend equivalents earned vest based on terms specified under the related RSU award agreement. Shares issued upon settlement of vested RSUs, including RSUs paid on dividend equivalents, are distributed in a single lump sum distribution upon the earlier of (1) the date specified by the participant when the election is made or (2) occurrence of certain other events specified under the RSU program. Share-Based Compensation Programs The Compensation Committee has historically awarded nonvested shares and RSUs under the share-based compensation programs described below. These share-based awards were valued based on the quoted closing share price of the Company’s common stock on the NYSE on the applicable grant date. The Compensation Committee grants annual long-term equity awards as an incentive for the year in which the awards are granted and subsequent years. Executive Officer and Key Employee Share-Based Compensation Programs The Compensation Committee has annually approved compensation programs that include the potential issuance of share-based awards to our executive officers and other key employees as part of their annual and long-term incentive compensation. The share-based awards are generally issued in the first quarter after the end of our prior fiscal year. The share-based awards generally have a service vesting period, which has historically ranged from one to five years, depending on the type of award. Non-Employee Board Member Share-Based Compensation Program The Board of Directors awards nonvested shares or nonvested RSUs to non-employee board members on an annual basis as part of such board members’ annual compensation and to newly elected non-employee board members in accordance with our Board of Directors compensation program. The share-based awards are generally issued in the second quarter, and the individual share awards vest in equal annual installments over the applicable service vesting period, which will be one year for the annual non-employee board awards and four years for the awards relating to newly elected non-employee board members. 2017, 2016 and 2015 Share-Based Compensation Grants In February 2017 , the Compensation Committee of the Company’s Board of Directors awarded 229,976 RSUs to certain officers of the Company under the 2006 Plan, which included 130,956 RSUs (at the target level of performance) that are subject to time-based, market-measure based and performance-based vesting requirements (the “2017 Performance-Based RSUs”) and 99,020 RSUs that are subject to time-based vesting requirements (the “2017 Time-Based RSUs”). Additionally, during 2017, 43,081 RSUs were granted to the board of directors and certain members of management subject to time vesting requirements. On January 28, 2016 , the Compensation Committee of the Company’s Board of Directors awarded 294,821 RSUs to certain officers of the Company under the 2006 Plan, which included 168,077 RSUs (at the target level of performance) that are subject to time-based, market-measure based and performance-based vesting requirements (the “2016 Performance-Based RSUs”) and 126,744 RSUs that are subject to time-based vesting requirements (“2016 Time-Based RSUs”). Additionally, during 2016, 47,003 RSUs were granted to the board of directors and certain members of management subject to time vesting requirements. On January 27, 2015 , the Compensation Committee of the Company’s Board of Directors awarded 212,468 RSUs to certain officers of the Company under the 2006 Plan, which included 127,657 RSUs (at the target level of performance), that are subject to time-based, market-measure based and performance-based vesting requirements (the “2015 Performance-Based RSUs”) and 84,811 RSUs, that are subject to time-based vesting requirements (“2015 Time-Based RSUs”). 2017, 2016 and 2015 Performance-Based RSU Grants The 2017 Performance-Based RSUs are scheduled to cliff vest at the end of a three -year period based upon the achievement of pre-defined FFO per share goals for the year ended December 31, 2017 (the “2017 FFO Performance Condition”) and also based upon either the average FAD per share growth or the Company’s average debt to EBITDA ratio (together, the “Other 2017 Performance Conditions”) or the relative total stockholder return versus a comparative group of companies that consist of companies in the SNL US REIT Office Index (the “2017 Market Condition”) for the three -year period ending December 31, 2019. The 2017 FFO Performance Condition was achieved at a weighted average of approximately 131% of target for the 2017 Performance-Based RSUs. The number of 2017 Performance-Based RSUs ultimately earned could fluctuate based upon the levels of achievement for the Other 2017 Performance Conditions and the 2017 Market Condition. The 2016 Performance-Based RSUs are also scheduled to cliff vest at the end of a three -year service period based upon the achievement of pre-defined FFO per share goals for the year ended December 31, 2016 (the “2016 FFO Performance Condition”) and also upon the average annual relative total stockholder return versus a comparative group of companies that consist of companies in the SNL US REIT Office Index (the “2016 Market Condition”) for the three -year period ending December 31, 2018. The 2016 FFO Performance Condition was achieved at approximately 144% of target for the 2016 Performance-Based RSUs. The number of 2016 Performance-Based RSUs ultimately earned could fluctuate based upon the levels of achievement for the 2016 Market Condition. The 2015 Performance-Based RSUs cliff vested at the end of the three -year service period based upon the achievement of pre-defined FFO per share goals for the year ended December 31, 2015 (the “2015 FFO Performance Condition”) and also upon the average annual relative total shareholder return versus a comparative group of companies that consist of companies in the SNL US REIT Office Index (the “2015 Market Condition”) for the three-year period ending December 31, 2017. Based upon the combined results of the final 2015 FFO Performance Condition and final 2015 Market Condition, the 2015 Performance-Based RSUs achieved 150% of their target level of performance. As of December 31, 2017 , the estimated number of RSUs earned for the 2017 and 2016 Performance-Based RSUs and the actual number of RSUs earned for the 2015 Performance-Based RSUs was as follows: 2017 Performance-Based RSUs 2016 Performance-Based RSUs 2015 Performance-Based RSUs Service vesting period February 24, 2017 - January, 2020 January 28, 2016 - January, 2019 January 27, 2015 - January, 2018 Target RSUs granted 130,956 168,077 127,657 Estimated RSUs earned (1) 170,994 241,438 185,510 Date of valuation February 24, 2017 January 28, 2016 January 27, 2015 _______________ (1) Estimated RSUs earned for the 2017 Performance-Based RSUs are based on the actual achievement of the 2017 FFO Performance Condition and assumes target level achievement of the 2017 Market Condition and Other Performance Conditions. Estimated RSUs earned for the 2016 Performance-Based RSUs are based on the actual achievement of the 2016 FFO Performance Condition and assumes target level achievement of the 2016 Market Condition. The 2015 Performance-Based RSUs earned are based on actual performance of the 2015 FFO Performance Condition and the 2015 Market Condition. Each Performance-Based RSU represents the right to receive one share of our common stock in the future, subject to, and as modified by, the Company’s level of achievement of the applicable performance and market conditions. The fair values of the 2017 Performance-Based RSUs, 2016 Performance-Based RSUs and 2015 Performance-Based RSUs were $10.3 million at February 24, 2017 , $9.6 million at January 28, 2016 and $10.1 million at January 27, 2015 , respectively. The fair values for the awards with market conditions were calculated using a Monte Carlo simulation pricing model based on the assumptions in the table below. The determination of the fair value of the 2017, 2016 and 2015 Performance-Based RSUs takes into consideration the likelihood of achievement of the 2017, 2016 and 2015 Performance Conditions and the 2017, 2016 and 2015 Market Conditions, respectively, as discussed above. As of December 31, 2017 , the number of 2017 Performance-Based RSUs estimated to be earned based on the Company's estimate of the performance conditions measured against the applicable goals was 170,994 , and the compensation cost recorded to date for this program was based on that estimate. For the portion of the 2017 Performance-Based RSUs subject to the 2017 Market Condition, for the year ended December 31, 2017 , we recorded compensation expense based upon the $80.89 fair value per share at February 24, 2017 . Compensation expense will be variable for the portion of the 2017 Performance-Based RSUs subject to the Other 2017 Performance Conditions, based upon the outcome of those conditions. For the years ended December 31, 2017 and 2016 , we recorded compensation expense for the 2016 Performance-Based RSUs based upon the $57.08 fair value per share at January 28, 2016 multiplied by the 241,438 RSUs, which is net of forfeitures, estimated to be earned at December 31, 2016 . For the years ended December 31, 2017 , 2016 and 2015 , we recorded compensation expense for the 2015 Performance-Based RSUs based upon $78.55 fair value per share at January 27, 2015 multiplied by the 185,510 RSUs, which is net of forfeitures, estimated to be earned at December 31, 2015. Compensation expense for the Performance-Based RSUs is recorded on a straight-line basis over the respective three-year periods. The following table summarizes the assumptions utilized in the Monte Carlo simulation pricing models: 2017 Award Fair Value Assumptions 2016 Award Fair Value Assumptions 2015 Award Fair Value Assumptions Valuation date February 24, 2017 January 28, 2016 January 27, 2015 Fair value per share on valuation date $80.89 $57.08 $75.34 Expected share price volatility 21.00% 26.00% 20.00% Risk-free interest rate 1.39% 1.13% 0.92% Expected life 2.8 years 2.9 years 2.9 years The computation of expected volatility was based on a blend of the historical volatility of our shares of common stock over approximately five years, as this is expected to be most consistent with future volatility and equates to a time period twice as long as the approximate two and a half year remaining performance period of the RSUs and implied volatility data based on the observed pricing of six month publicly-traded options on shares of our common stock. The risk-free interest rate was based on the yield curve on zero-coupon U.S. Treasury STRIP securities in effect at February 24, 2017 , January 28, 2016 and January 27, 2015 . 2017, 2016 and 2015 Time-Based RSU Grants The 2017, 2016 and 2015 Time-Based RSUs (collectively, the “Time-Based RSUs”) are scheduled to vest in equal installments over the periods listed below. Compensation expense for the Time-Based RSUs will be recognized on a straight-line basis from the grant date through the continued service vesting periods. Each Time-Based RSU represents the right to receive one share of our common stock in the future, subject to continued employment through the applicable vesting date. The total fair value of the Time-Based RSUs is based on the Company's closing share price on the NYSE on the respective fair valuation dates as detailed in the table below: 2017 Time-Based RSU Grant (1) 2016 Time-Based RSU Grant 2015 Time-Based RSU Grant Service vesting period February 2017 - January 5, 2020 January 28, 2016 - January 5, 2019 January 27, 2015 - January 5, 2018 Fair value on valuation date (in millions) $ 7.5 $ 7.1 $ 6.4 Fair value per share $ 73.30 $ 56.23 $ 75.34 Date of fair valuation February 2017 January 28, 2016 January 27, 2015 _______________ (1) The 2017 Time-Based RSUs consist of 41,119 RSUs granted on February 3, 2017 at a fair value per share of $73.30 and 57,901 RSUs granted on February 24, 2017 at a fair value per share of $77.16 . Summary of Performance and Market-Measure Based RSUs A summary of our performance and market-measure based RSU activity from January 1, 2017 through December 31, 2017 is presented below: Nonvested RSUs Vested RSUs Total RSUs Amount Weighted-Average (1) Outstanding at January 1, 2017 659,051 $ 64.95 — 659,051 Granted 170,994 78.97 — 170,994 Vested (188,048 ) 64.93 188,048 — Settled (2) (136,191 ) (136,191 ) Issuance of dividend equivalents (3) 23,539 73.00 6,943 30,482 Forfeited (426 ) 78.55 (3,128 ) (3,554 ) Outstanding as of December 31, 2017 (4) 665,110 $ 68.83 55,672 720,782 _______________ (1) Represents the grant-date fair value for all awards, excluding the 2014 Performance-Based RSU Grant, which was re-measured upon stockholder approval of the amended 2006 Plan on May 22, 2014, as an insufficient number of shares were available to settle these RSUs upon initial grant on January 29, 2014. (2) Represents vested RSUs that were settled in shares of the Company’s common stock. Total shares settled include 72,938 shares that were tendered in accordance with the terms of the 2006 Plan to satisfy minimum statutory tax withholding requirements related to the RSUs settled. We accept the return of RSUs at the current quoted closing share price of the Company’s common stock to satisfy tax obligations. (3) Represents the issuance of dividend equivalents earned on the underlying RSUs. The dividend equivalents vest based on terms specified under the related RSU award agreement. (4) Outstanding RSUs as of December 31, 2017 represent the actual achievement of the FFO performance conditions and assumes target levels for the market and other performance conditions. The number of restricted stock units ultimately earned is subject to change based upon actual performance over the three-year vesting period. Dividend equivalents earned will vest along with the underlying award and are also subject to changes based on the number of RSUs ultimately earned for each underlying award. A summary of our performance and market-measure based RSU activity for years ended December 31, 2017 , 2016 and 2015 is presented below: RSUs Granted RSUs Vested Years ended December 31, Non-Vested RSUs Granted (1) Weighted-Average Fair Value Per Share (2) Vested RSUs Total Vest-Date Fair Value (in thousands) 2017 170,994 $ 78.97 (194,991 ) $ 14,270 2016 258,393 57.36 (36,914 ) 2,788 2015 191,483 79.25 — — _______________ (1) Non-vested RSUs granted during the years ended December 31, 2017 and 2016 are based on the actual achievement of the FFO performance conditions and assumes target level achievement for the market and other performance conditions. Non-vested RSUs granted during the year ended December 31, 2015 are based on the final performance of both the 2015 FFO performance and market conditions, and are non-vested as of December 31, 2017 as they are subject to the Compensation Committee’s confirmation of final performance. (2) Represents the grant-date fair value for all awards, excluding the 2014 Performance-Based RSU Grant, which was re-measured upon stockholder approval of the amended 2006 Plan on May 22, 2014, as an insufficient number of shares were available to settle these RSUs upon initial grant on January 29, 2014. Summary of Time-Based RSUs A summary of our time-based RSU activity from January 1, 2017 through December 31, 2017 is presented below: Nonvested RSUs Vested RSUs Total RSUs Amount Weighted Average Fair Value (1) Outstanding at January 1, 2017 366,439 $ 59.07 1,028,750 1,395,189 Granted 142,101 74.91 — 142,101 Vested (172,731 ) 57.77 172,731 — Settled (2) (171,093 ) (171,093 ) Issuance of dividend equivalents (3) 8,601 73.00 55,364 63,965 Transferred to restricted stock (4) (10,610 ) 60.16 — (10,610 ) Forfeited (2,254 ) 63.27 — (2,254 ) Canceled (5) (4,824 ) (4,824 ) Outstanding as of December 31, 2017 331,546 $ 66.83 1,080,928 1,412,474 _______________ (1) Represents the grant-date fair value for all awards, excluding the 2014 Performance-Based RSU Grant, which was re-measured upon stockholder approval of the amended 2006 Plan on May 22, 2014, as an insufficient number of shares were available to settle these RSUs upon initial grant on January 29, 2014. (2) Represents vested RSUs that were settled in shares of the Company’s common stock. Total shares settled include 77,866 shares that were tendered in accordance with the terms of the 2006 Plan to satisfy minimum statutory tax withholding requirements related to the RSUs settled. We accept the return of RSUs at the current quoted closing share price of the Company’s common stock to satisfy tax obligations. (3) Represents the issuance of dividend equivalents earned on the underlying RSUs. The dividend equivalents vest based on terms specified under the related RSU award agreement. (4) During January 2017, RSUs were transferred to restricted stock based on the elected distribution date. (5) For shares vested but not yet settled, we accept the return of RSUs at the current quoted closing share price of the Company’s common stock to satisfy minimum statutory tax-withholding requirements related to either the settlement or vesting of RSUs in accordance with the terms of the 2006 Plan. A summary of our time-based RSU activity for the years ended December 31, 2017 , 2016 and 2015 is presented below: RSUs Granted RSUs Vested Year ended December 31, Non-Vested RSUs Issued Weighted-Average Grant Date Fair Value Per Share Vested RSUs Total Vest-Date Fair Value (1) (in thousands) 2017 142,101 $ 74.91 (228,095 ) $ 16,735 2016 173,747 58.29 (130,784 ) 8,438 2015 98,802 74.49 (107,541 ) 7,528 _______________ (1) Total fair value of RSUs vested was calculated based on the quoted closing share price of the Company’s common stock on the NYSE on the day of vesting. Excludes the issuance of dividend equivalents earned on the underlying RSUs. The dividend equivalents vest based on terms specified under the related RSU award agreement. Summary of Nonvested Restricted Stock A summary of our nonvested restricted stock activity from January 1, 2017 through December 31, 2017 is presented below: Nonvested Weighted-Average Outstanding at January 1, 2017 36,535 $ 47.93 Transferred from time-based RSUs 10,610 60.16 Vested (1) (24,261 ) 46.39 Outstanding as of December 31, 2017 22,884 $ 55.23 _______________ (1) The total shares vested includes 10,792 shares that were tendered in accordance with the terms of the 2006 Plan to satisfy minimum statutory tax withholding requirements related to the restricted shares that have vested. We accept the return of shares at the current quoted closing share price of the Company’s common stock to satisfy tax withholding obligations. A summary of our nonvested and vested restricted stock activity for years ended December 31, 2017 , 2016 and 2015 is presented below: Shares Granted Shares Vested Years ended December 31, Nonvested Shares Issued Weighted-Average Grant Date Fair Value Per Share Vested Shares Total Fair Value at Vest Date (1) (in thousands) 2017 — $ — (24,261 ) $ 1,781 2016 — — (24,262 ) 1,527 2015 — — (24,264 ) 1,725 _______________ (1) Total fair value of shares vested was calculated based on the quoted closing share price of the Company’s common stock on the NYSE on the date of vesting. Summary of Stock Options On February 22, 2012, the Compensation Committee of the Company granted non-qualified stock options to certain key members of our senior management team, including our Executive Officers, to purchase an aggregate 1,550,000 shares of the Company’s common stock (the “February 2012” Grant) at an exercise price per share equal to $42.61 , the closing price of the Company’s common stock on the grant date. The options will vest ratably in annual installments over a five year period, subject to continued employment through the applicable vesting date. The term of each option is ten years from the date of the grant. Dividends will not be paid on vested or unvested options. The options were granted pursuant to the 2006 Plan. The fair value of each stock option granted is estimated on the date of grant using the Black-Scholes option pricing model based on the following assumptions for the February 2012 Grant. February 2012 Option Grant Fair value of options granted per share $9.20 Expected stock price volatility 33.00% Risk-free interest rate 1.35% Dividend yield 3.80% Expected life of option 6.5 years The computation of expected volatility is based on a blend of the historical volatility of our shares of common stock over a time period longer than the expected life of the option 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 the grant date. The expected dividend yield is estimated by examining the average of the historical dividend yield levels over the expected life of the option and the current dividend yield as of the grant date. The expected life of the options is calculated as the average of the vesting term and the contractual term. During the years ended December 31, 2017 , 2016 and 2015 , 261,000 , 267,000 and 298,000 stock options vested, respectively, with a total fair value of $2.4 million , $2.5 million and $2.7 million , respectively. A summary of our stock option activity related to the February 2012 grant from January 1, 2017 through December 31, 2017 is presented below: Number of Options Exercise Price Intrinsic Value (in millions) (1) Outstanding at December 31, 2016 314,500 $ 42.61 $ 9.6 Exercised (285,000 ) 42.61 8.8 Forfeited (3,000 ) 42.61 0.1 Outstanding at December 31, 2017 (2) 26,500 $ 42.61 $ 0.8 Options exercisable at December 31, 2017 (3) 26,500 $ 42.61 $ 0.8 _______________ (1) The intrinsic value of a stock option is the amount by which the fair value of the underlying stock exceeds the exercise price of an option. The fair value of the underlying stock was determined by using the closing share price on the NYSE on the date of exercise, forfeiture or respective period end. (2) As of December 31, 2017 , the average remaining life of stock options outstanding was 4.1 years. (3) As of December 31, 2017 , the average remaining life of stock options exercisable was approximately 4.1 years. In accordance with the provisions of the 2006 Plan, we allow shares of our common stock to be withheld to satisfy the payment of exercise price and/or minimum statutory tax withholding obligations due upon the exercise of stock options. The value of the shares withheld is calculated based on the closing market price of our common stock on the NYSE on the day prior to the exercise date. During the year ended December 31, 2017 , 15,270 shares were withheld on stock option exercises with an aggregate value of $1.2 million . During the year ended December 31, 2016 , 25,680 shares were withheld on stock option exercises with an aggregate value of $1.8 million . During the year ended December 31, 2015 , 62,072 shares were withheld on stock option exercises with an aggregate value of $3.9 million . Share-Based Compensation Cost Recorded During the Period The total compensation cost for all share-based compensation programs was $26.3 million , $26.6 million and $18.9 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. Of the total share-based compensation costs, $7.3 million , $5.6 million and $3.3 million was capitalized as part of real estate assets and deferred leasing costs for the years ended December 31, 2017 , 2016 and 2015 , respectively. As of December 31, 2017 , there was approximately $27.2 million of total unrecognized compensation cost related to nonvested incentive awards granted under share-based compensation arrangements that is expected to be recognized over a weighted-average period of 1.9 years. The remaining compensation cost related to these nonvested incentive awards had been recognized in periods prior to December 31, 2017 . The $27.2 million of unrecognized compensation costs does not reflect the future compensation cost related to share-based awards that were granted subsequent to December 31, 2017 .

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Employee Benefit Plans	Employee Benefit Plans 401(k) Plan We have a retirement savings plan designed to qualify under Section 401(k) of the Code (the “401(k) Plan”). Our employees are eligible to participate in the 401(k) Plan on the first day of the month after three months of service. The 401(k) Plan allows eligible employees (“401(k) Participants”) to defer up to 60% of their eligible compensation on a pre-tax basis, subject to certain maximum amounts allowed by the Code. The 401(k) Plan provides for a matching contribution by the Company in an amount equal to 50 cents of each one dollar of participant contributions up to a maximum of 10% of the 401(k) Participant’s annual salary. 401(k) Participants vest immediately in the amounts contributed by us. For each of the years ended December 31, 2017 , 2016 , and 2015 , we contributed $1.3 million , $1.2 million and $1.1 million , respectively, to the 401(k) Plan. Deferred Compensation Plan In 2007, we adopted the Deferred Compensation Plan, under which directors and certain management employees may defer receipt of their compensation, including up to 70% of their salaries and up to 100% of their director fees and bonuses, as applicable. In addition, employee participants will receive mandatory Company contributions to their Deferred Compensation Plan accounts equal to 10% of their gross monthly salaries, without regard to whether such employees elect to defer salary or bonus compensation under the Deferred Compensation Plan. Our board of directors may, but has no obligation to, approve additional discretionary contributions by the Company to Participant accounts. We hold the Deferred Compensation Plan assets in a limited rabbi trust, which is subject to the claims of our creditors in the event of bankruptcy or insolvency. See Note 19 “Fair Value Measurements and Disclosures” for further discussion of our Deferred Compensation Plan assets as of December 31, 2017 and 2016 . Our liability of $20.6 million and $14.7 million under the Deferred Compensation Plan was fully funded as of December 31, 2017 and 2016 , respectively.

Future Minimum Rent

Future Minimum Rent	12 Months Ended
	Dec. 31, 2017
Leases [Abstract]
Future Minimum Rent	Future Minimum Rent We have operating leases with tenants that expire at various dates through 2037 and are either subject to scheduled fixed increases or adjustments in rent based on the Consumer Price Index. Generally, the leases grant tenants renewal options. Leases also provide for additional rents based on certain operating expenses. Future contractual minimum rent under operating leases as of December 31, 2017 for future periods is summarized as follows: Year Ending (in thousands) 2018 $ 555,393 2019 546,587 2020 525,637 2021 497,566 2022 476,146 Thereafter 2,569,163 Total (1) $ 5,170,492 ______________ (1) Excludes residential leases and leases with a term of one year or less.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies General As of December 31, 2017 , we had commitments of approximately $696.1 million , excluding our ground lease commitments, for contracts and executed leases directly related to our operating and development properties. Ground Leases The following table summarizes our properties that are held subject to long-term noncancellable ground lease obligations and the respective contractual expiration dates: Property Contractual Expiration Date (1) 601 108th Ave NE, Bellevue, WA November 2093 701, 801 and 837 N. 34th Street, Seattle, WA (2) December 2041 1701 Page Mill Road and 3150 Porter Drive, Palo Alto, CA December 2067 Kilroy Airport Center Phases I, II, and III, Long Beach, CA July 2084 ____________________ (1) Reflects the contractual expiration date prior to the impact of any extension or purchase options held by the Company. (2) The Company has three 10 -year and one 45 -year extension options for this ground lease, which if exercised would extend the expiration date to December 2116. The minimum commitment under our ground leases as of December 31, 2017 for five years and thereafter is as follows: Year Ending (in thousands) 2018 $ 4,957 2019 4,957 2020 4,957 2021 4,957 2022 4,957 Thereafter 226,633 Total (1)(2)(3)(4)(5) $ 251,418 ________________________ (1) Excludes contingent future rent payments based on gross income or adjusted gross income and reflects the minimum ground lease obligations before the impact of ground lease extension options. (2) One of our ground lease obligations is subject to a fair market value adjustment every five years ; however, the lease includes ground rent subprotection and infrastructure rent credits which currently limit our annual rental obligations to $1.0 million . The contractual obligations for that ground lease included above assumes the lesser of $1.0 million or annual lease rental obligation in effect as of December 31, 2017 . (3) One of our ground lease obligations includes a component which is based on the percentage of gross income that exceeds the minimum ground rent. The minimum rent is subject to increases every five years based on 50% of the average annual percentage rent for the previous five years. The contractual obligations for that lease included above assume the current annual ground lease obligation in effect at December 31, 2017 for the remainder of the lease term since we cannot predict future adjustments. (4) One of our ground lease obligations is subject to a fair market value adjustment every five years based on a combination of CPI adjustments and third-party appraisals limited to maximum increases annually. The contractual obligations for that lease included above assume the current annual ground lease obligation in effect at December 31, 2017 for the remainder of the lease term since we cannot predict future adjustments. (5) One of our ground lease obligations includes a component which is based on the percentage of adjusted gross income that exceeds the minimum ground rent. The minimum rent is subject to increases every 10 years by an amount equal to 60% of the average annual percentage rent for the previous three years. The contractual obligations for this lease included above assume the current annual ground lease obligation in effect at December 31, 2017 for the remainder of the lease term since we cannot predict future adjustments. 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 December 31, 2017 and 2016 , we had accrued environmental remediation liabilities of approximately $28.3 million and $25.1 million , respectively, recorded on our consolidated balance sheets in connection with certain of our in-process and future development projects. The accrued environmental remediation liabilities represent the costs we estimate we will incur when we commence development at various development acquisition sites. These estimates, which we developed with the assistance of third party experts, consist primarily of the removal of contaminated soil and other related costs since we are required to dispose of any existing contaminated soil when we develop new office properties as these sites. We record estimated environmental remediation obligations for acquired properties at the acquisition date when we are aware of such costs and when such costs are probable and can be reasonably estimated. Costs incurred in connection with the development related environmental remediation liabilities are recorded as an increase to the cost of the development project. These accruals are adjusted as an increase or decrease to the development project costs and as an increase or decrease to the accrued environmental remediation liability if we obtain further information or circumstances change. The environmental remediation obligations recorded at December 31, 2017 and 2016 were not discounted to their present value since we expect to complete the remediation activities in the next one to five years in connection with development activities at the various sites. 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. Other than the accrued environmental liabilities discussed above, we are not aware of any unasserted claims and assessments with respect to an environmental liability that we believe would require additional disclosure or the recording of an additional loss contingency. Litigation We and our properties are subject to litigation arising in the ordinary course of business. To our knowledge, neither we nor any of our properties are presently subject to any litigation or threat of litigation which, if determined unfavorably to us, would have a material adverse effect on our cash flow, financial condition, or results of operations. Insurance We maintain commercial general liability, auto liability, employers’ liability, umbrella/excess liability, special form property, difference in conditions including earthquake and flood, environmental, rental loss, and terrorism insurance covering all of our properties. Management believes the policy specifications and insured limits are reasonable given the relative risk of loss, the cost of the coverage, and industry practice. We do not carry insurance for generally uninsurable losses such as loss from governmental action, nuclear hazard, and war and military action. Policies are subject to various terms, conditions, and exclusions and some policies may involve large deductibles or co-payments. Property Damage Settlement During the year ended December 31, 2016 , we settled an outstanding property damage matter and received cash proceeds totaling $5.0 million , which is included in other property income on our consolidated statements of operations.

Fair Value Measurements and Dis

Fair Value Measurements and Disclosures	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements and Disclosures	Fair Value Measurements and Disclosures Assets and Liabilities Reported at Fair Value The only assets we record at fair value on our consolidated financial statements are the marketable securities related to our Deferred Compensation Plan (see Note 16 “Employee Benefit Plans” for additional information). The following table sets forth the fair value of our marketable securities as of December 31, 2017 and 2016 : Fair Value (Level 1) (1) 2017 2016 Description (in thousands) Marketable securities (2) $ 20,674 $ 14,773 _______________ (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 gains (losses) 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 gain (loss) on marketable securities recorded during the years ended December 31, 2017 , 2016 and 2015 : December 31, 2017 2016 2015 Description (in thousands) Net gain (loss) on marketable securities $ 3,023 $ 1,130 $ (269 ) Financial Instruments Disclosed at Fair Value The following table sets forth the carrying value and the fair value of our other financial instruments as of December 31, 2017 and 2016 : December 31, 2017 2016 Carrying Value Fair Value (1) Carrying Value Fair Value (1) (in thousands) Liabilities Secured debt, net $ 340,800 $ 346,858 $ 472,772 $ 469,234 Unsecured debt, net 2,006,263 2,077,199 1,847,351 1,900,487 _______________ (1) Fair value calculated using Level II inputs, which are based on model-derived valuations in which significant inputs and significant value drivers are observable in active markets.

Net Income Available to Common

Net Income Available to Common Stockholders Per Share of the Company	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Net Income Available to Common Stockholders Per Share of the Company	Net Income Available to Common Stockholders Per Share of the Company The following table reconciles the numerator and denominator in computing the Company’s basic and diluted per-share computations for net income available to common stockholders for the years ended December 31, 2017 , 2016 and 2015 : Year Ended December 31, 2017 2016 2015 (in thousands, except unit and per unit amounts) Numerator: Net income attributable to Kilroy Realty Corporation $ 164,612 $ 293,788 $ 234,081 Total preferred dividends (13,363 ) (13,250 ) (13,250 ) Allocation to participating securities (1) (1,975 ) (3,839 ) (1,634 ) Numerator for basic and diluted net income available to common stockholders $ 149,274 $ 276,699 $ 219,197 Denominator: Basic weighted average vested shares outstanding 98,113,561 92,342,483 89,854,096 Effect of dilutive securities – contingently issuable shares and stock options 613,770 680,551 541,679 Diluted weighted average vested shares and common stock equivalents outstanding 98,727,331 93,023,034 90,395,775 Basic earnings per share: Net income available to common stockholders per share $ 1.52 $ 3.00 $ 2.44 Diluted earnings per share: Net income available to common stockholders per share $ 1.51 $ 2.97 $ 2.42 ________________________ (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 years ended December 31, 2017 , 2016 , and 2015 . Certain market measure-based RSUs are not included in dilutive securities as of December 31, 2017 , 2016 , and 2015 as not all performance metrics had been met by the end of the applicable reporting periods. See Note 15 “Share-Based Compensation” for additional information regarding the stock options and other share-based compensation.

Net Income Available to Commo34

Net Income Available to Common Unitholders Per Unit of the Operating Partnership	12 Months Ended
	Dec. 31, 2017
Kilroy Realty, L.P. [Member]
Net Income Available To Common Unitholders [Line Items]
Net Income Available to Common Unitholders per Unit of the Operating Partnership	Net Income Available to Common Unitholders Per Unit of the Operating Partnership The following table reconciles the numerator and denominator in computing the Operating Partnership’s basic and diluted per-unit computations for net income available to common unitholders for the years ended December 31, 2017 , 2016 and 2015 : Year Ended December 31, 2017 2016 2015 (in thousands, except unit and per unit amounts) Numerator: Net income attributable to Kilroy Realty, L.P. $ 167,440 $ 300,063 $ 238,137 Total preferred distributions (13,363 ) (13,250 ) (13,250 ) Allocation to participating securities (1) (1,975 ) (3,839 ) (1,634 ) Numerator for basic and diluted net income available to common unitholders $ 152,102 $ 282,974 $ 223,253 Denominator: Basic weighted average vested units outstanding 100,246,567 94,771,688 91,645,578 Effect of dilutive securities - contingently issuable shares and stock options 613,770 680,551 541,679 Diluted weighted average vested units and common unit equivalents outstanding 100,860,337 95,452,239 92,187,257 Basic earnings per unit: Net income available to common unitholders per unit $ 1.52 $ 2.99 $ 2.44 Diluted earnings per unit: Net income available to common unitholders per unit $ 1.51 $ 2.96 $ 2.42 ________________________ (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 years ended December 31, 2017 , 2016 , and 2015 . Certain market measure-based RSUs are not included in dilutive securities as of December 31, 2017 and 2016 as not all performance metrics had been met by the end of the applicable reporting periods. See Note 15 “Share-Based Compensation” for additional information regarding the stock options and other share-based compensation.

Supplemental Cash Flow Informat

Supplemental Cash Flow Information of the Company	12 Months Ended
	Dec. 31, 2017
Supplemental Cash Flow Elements [Abstract]
Supplemental Cash Flow Information of the Company	Supplemental Cash Flow Information of the Company Supplemental cash flow information follows (in thousands): Year Ended December 31, 2017 2016 2015 SUPPLEMENTAL CASH FLOWS INFORMATION: Cash paid for interest, net of capitalized interest of $44,757, $47,675, and $50,923 as of December 31, 2017, 2016 and 2015, respectively $ 67,336 $ 54,295 $ 54,747 NON-CASH INVESTING TRANSACTIONS: Accrual for expenditures for operating properties and development and redevelopment properties $ 116,089 $ 62,589 $ 109,715 Tenant improvements funded directly by tenants $ 15,314 $ 18,050 $ 13,387 Assumption of other assets and liabilities in connection with operating and development property acquisitions, net (Note 3) $ 1,443 $ 5,863 $ 6,254 Accrual for receivable related to development properties $ — $ 1,350 $ — Release of holdback funds to third party $ — $ — $ 9,279 NON-CASH FINANCING TRANSACTIONS: Accrual of dividends and distributions payable to common stockholders and common unitholders (Notes 13 and 27) $ 43,448 $ 220,650 $ 33,336 Accrual of dividends and distributions payable to preferred stockholders and preferred unitholders (Note 13) $ — $ 1,656 $ 1,656 Issuance of common units of the Operating Partnership in connection with an acquisition $ — $ 48,033 $ — Secured debt assumed by buyers in connection with land disposition (Note 4) $ — $ 2,322 $ — Exchange of common units of the Operating Partnership into shares of the Company’s common stock $ 10,939 $ 8,893 $ 1,223 The following is a reconciliation of our cash and cash equivalents and restricted cash at the beginning and end of the years ended December 31, 2017 , 2016 and 2015 . Year Ended December 31, 2017 2016 2015 RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH: Cash and cash equivalents at beginning of period $ 193,418 $ 56,508 $ 23,781 Restricted cash at beginning of period 56,711 696 75,185 Cash and cash equivalents and restricted cash at beginning of period $ 250,129 $ 57,204 $ 98,966 Cash and cash equivalents at end of period $ 57,649 $ 193,418 $ 56,508 Restricted cash at end of period 9,149 56,711 696 Cash and cash equivalents and restricted cash at end of period $ 66,798 $ 250,129 $ 57,204 Supplemental Cash Flow Information of the Operating Partnership: Supplemental cash flow information follows (in thousands): Year Ended December 31, 2017 2016 2015 SUPPLEMENTAL CASH FLOWS INFORMATION: Cash paid for interest, net of capitalized interest of $44,757, $47,675, and $50,923 as of December 31, 2017, 2016 and 2015, respectively $ 67,336 $ 54,295 $ 54,747 NON-CASH INVESTING TRANSACTIONS: Accrual for expenditures for operating properties and development and redevelopment properties $ 116,089 $ 62,589 $ 109,715 Tenant improvements funded directly by tenants $ 15,314 $ 18,050 $ 13,387 Assumption of other assets and liabilities in connection with operating and development property acquisitions, net (Note 3) $ 1,443 $ 5,863 $ 6,254 Accrual for receivable related to development properties $ — $ 1,350 $ — Release of holdback funds to third party $ — $ — $ 9,279 NON-CASH FINANCING TRANSACTIONS: Accrual of dividends and distributions payable to common stockholders and common $ 43,448 $ 220,650 $ 33,336 Accrual of dividends and distributions payable to preferred stockholders and preferred unitholders (Note 14) $ — $ 1,656 $ 1,656 Issuance of common units in connection with a development property acquisition (Note 3) $ — $ 48,033 $ — Secured debt assumed by buyers in connection with land disposition (Note 4) $ — $ 2,322 $ — The following is a reconciliation of our cash and cash equivalents and restricted cash at the beginning and end of the years ended December 31, 2017 , 2016 and 2015 . Year Ended December 31, 2017 2016 2015 RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH: Cash and cash equivalents at beginning of period $ 193,418 $ 56,508 $ 23,781 Restricted cash at beginning of period 56,711 696 75,185 Cash and cash equivalents and restricted cash at beginning of period $ 250,129 $ 57,204 $ 98,966 Cash and cash equivalents at end of period $ 57,649 $ 193,418 $ 56,508 Restricted cash at end of period 9,149 56,711 696 Cash and cash equivalents and restricted cash at end of period $ 66,798 $ 250,129 $ 57,204

Supplemental Cash Flow Inform36

Supplemental Cash Flow Information of the Operating Partnership	12 Months Ended
	Dec. 31, 2017
Supplemental Cash Flow Elements [Abstract]
Supplemental Cash Flow Information of the Operating Partnership	Supplemental Cash Flow Information of the Company Supplemental cash flow information follows (in thousands): Year Ended December 31, 2017 2016 2015 SUPPLEMENTAL CASH FLOWS INFORMATION: Cash paid for interest, net of capitalized interest of $44,757, $47,675, and $50,923 as of December 31, 2017, 2016 and 2015, respectively $ 67,336 $ 54,295 $ 54,747 NON-CASH INVESTING TRANSACTIONS: Accrual for expenditures for operating properties and development and redevelopment properties $ 116,089 $ 62,589 $ 109,715 Tenant improvements funded directly by tenants $ 15,314 $ 18,050 $ 13,387 Assumption of other assets and liabilities in connection with operating and development property acquisitions, net (Note 3) $ 1,443 $ 5,863 $ 6,254 Accrual for receivable related to development properties $ — $ 1,350 $ — Release of holdback funds to third party $ — $ — $ 9,279 NON-CASH FINANCING TRANSACTIONS: Accrual of dividends and distributions payable to common stockholders and common unitholders (Notes 13 and 27) $ 43,448 $ 220,650 $ 33,336 Accrual of dividends and distributions payable to preferred stockholders and preferred unitholders (Note 13) $ — $ 1,656 $ 1,656 Issuance of common units of the Operating Partnership in connection with an acquisition $ — $ 48,033 $ — Secured debt assumed by buyers in connection with land disposition (Note 4) $ — $ 2,322 $ — Exchange of common units of the Operating Partnership into shares of the Company’s common stock $ 10,939 $ 8,893 $ 1,223 The following is a reconciliation of our cash and cash equivalents and restricted cash at the beginning and end of the years ended December 31, 2017 , 2016 and 2015 . Year Ended December 31, 2017 2016 2015 RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH: Cash and cash equivalents at beginning of period $ 193,418 $ 56,508 $ 23,781 Restricted cash at beginning of period 56,711 696 75,185 Cash and cash equivalents and restricted cash at beginning of period $ 250,129 $ 57,204 $ 98,966 Cash and cash equivalents at end of period $ 57,649 $ 193,418 $ 56,508 Restricted cash at end of period 9,149 56,711 696 Cash and cash equivalents and restricted cash at end of period $ 66,798 $ 250,129 $ 57,204 Supplemental Cash Flow Information of the Operating Partnership: Supplemental cash flow information follows (in thousands): Year Ended December 31, 2017 2016 2015 SUPPLEMENTAL CASH FLOWS INFORMATION: Cash paid for interest, net of capitalized interest of $44,757, $47,675, and $50,923 as of December 31, 2017, 2016 and 2015, respectively $ 67,336 $ 54,295 $ 54,747 NON-CASH INVESTING TRANSACTIONS: Accrual for expenditures for operating properties and development and redevelopment properties $ 116,089 $ 62,589 $ 109,715 Tenant improvements funded directly by tenants $ 15,314 $ 18,050 $ 13,387 Assumption of other assets and liabilities in connection with operating and development property acquisitions, net (Note 3) $ 1,443 $ 5,863 $ 6,254 Accrual for receivable related to development properties $ — $ 1,350 $ — Release of holdback funds to third party $ — $ — $ 9,279 NON-CASH FINANCING TRANSACTIONS: Accrual of dividends and distributions payable to common stockholders and common $ 43,448 $ 220,650 $ 33,336 Accrual of dividends and distributions payable to preferred stockholders and preferred unitholders (Note 14) $ — $ 1,656 $ 1,656 Issuance of common units in connection with a development property acquisition (Note 3) $ — $ 48,033 $ — Secured debt assumed by buyers in connection with land disposition (Note 4) $ — $ 2,322 $ — The following is a reconciliation of our cash and cash equivalents and restricted cash at the beginning and end of the years ended December 31, 2017 , 2016 and 2015 . Year Ended December 31, 2017 2016 2015 RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH: Cash and cash equivalents at beginning of period $ 193,418 $ 56,508 $ 23,781 Restricted cash at beginning of period 56,711 696 75,185 Cash and cash equivalents and restricted cash at beginning of period $ 250,129 $ 57,204 $ 98,966 Cash and cash equivalents at end of period $ 57,649 $ 193,418 $ 56,508 Restricted cash at end of period 9,149 56,711 696 Cash and cash equivalents and restricted cash at end of period $ 66,798 $ 250,129 $ 57,204

Tax Treatment of Distributions

Tax Treatment of Distributions	12 Months Ended
	Dec. 31, 2017
Tax Treatment of Distributions [Abstract]
Tax Treatment of Distributions	Tax Treatment of Distributions The following table reconciles the dividends declared per share of common stock to the dividends paid per share of common stock during the years ended December 31, 2017 , 2016 and 2015 as follows: Year Ended December 31, Dividends 2017 2016 2015 Dividends declared per share of common stock $ 1.650 $ 3.375 $ 1.400 Less: Dividends declared in the current year and paid in the following year (0.425 ) (2.275 ) (0.350 ) Add: Dividends declared in the prior year and paid in the current year (1) 2.275 0.350 0.350 Dividends paid per share of common stock $ 3.500 $ 1.450 $ 1.400 _________________ (1) The fourth quarter 2016 dividend of $2.275 per share of common stock consists of a special cash dividend of $1.90 per share of common stock and a regular quarterly cash dividend of $0.375 per share of common stock. The $1.90 per share special distribution is treated as paid in two tax years for income tax purposes: $1.587 is treated as paid on December 31, 2016 and $0.313 is treated as paid on January 13, 2017. The $0.375 per share regular quarterly distribution is considered a 2017 dividend distribution for income tax purposes. The unaudited income tax treatment for the dividends to common stockholders reportable for the years ended December 31, 2017 , 2016 and 2015 as identified in the table above was as follows: Year Ended December 31, Shares of Common Stock 2017 2016 2015 Ordinary income $ 1.356 70.87 % $ 1.500 49.40 % $ 0.992 70.86 % Qualified dividend 0.002 0.11 0.002 0.06 0.002 0.13 Return of capital 0.344 18.00 — — — — Capital gains (1) — — 1.212 39.89 0.051 3.65 Unrecaptured section 1250 gains 0.211 11.02 0.323 10.65 0.355 25.36 $ 1.913 100.00 % $ 3.037 100.00 % $ 1.400 100.00 % _________________ (1) Capital gains are comprised entirely of 20% rate gains. The 6.875% Series G Cumulative Redeemable Preferred Stock was issued in March 2012 and redeemed in March 2017. The unaudited income tax treatment for the dividends to Series G preferred stockholders reportable for the years ended December 31, 2017 , 2016 , and 2015 was as follows: Year Ended December 31, Preferred Shares 2017 2016 2015 Ordinary income $ 0.371 86.43 % $ 0.848 49.31 % $ 1.218 70.86 % Qualified dividend 0.001 0.14 0.001 0.06 0.002 0.13 Capital gains (1) — — 0.687 39.97 0.063 3.65 Unrecaptured section 1250 gains 0.058 13.43 0.183 10.66 0.436 25.36 $ 0.430 100.00 % $ 1.719 100.00 % $ 1.719 100.00 % __________________ (1) Capital gains are comprised entirely of 20% rate gains. The 6.375% Series H Cumulative Redeemable Preferred Stock was issued in August 2012 and redeemed in August 2017. The unaudited income tax treatment for the dividends to Series H preferred stockholders reportable for the years ended December 31, 2017 , 2016 , and 2015 was as follows: Year Ended December 31, Preferred Shares 2017 2016 2015 Ordinary income $ 1.033 86.43 % $ 0.786 49.31 % $ 1.129 70.86 % Qualified dividend 0.002 0.14 0.001 0.06 0.002 0.13 Capital gains (1) — — 0.637 39.97 0.059 3.65 Unrecaptured section 1250 gains 0.160 13.43 0.17 10.66 0.404 25.36 $ 1.195 100.00 % $ 1.594 100.00 % $ 1.594 100.00 % __________________ (1) Capital gains are comprised entirely of 20% rate gains.

Quarterly Financial Information

Quarterly Financial Information of the Company (Unaudited)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information of the Company (Unaudited)	Quarterly Financial Information of the Company (Unaudited) Summarized quarterly financial data for the years ended December 31, 2017 and 2016 was as follows: 2017 Quarter Ended (1) March 31, June 30, September 30, December 31, (in thousands, except per share amounts) Revenues $ 179,308 $ 180,598 $ 181,534 $ 177,561 Net income 37,281 35,306 75,488 32,540 Net income attributable to Kilroy Realty Corporation 33,525 31,448 71,110 28,529 Total preferred dividends and distributions (7,196 ) (1,615 ) (4,552 ) — Net income available to common stockholders 26,329 29,833 66,558 28,529 Net income available to common stockholders per share – basic 0.27 0.30 0.67 0.28 Net income available to common stockholders per share – diluted 0.26 0.30 0.67 0.28 2016 Quarter Ended (1) March 31, June 30, September 30, December 31, (in thousands, except per share amounts) Revenues $ 145,446 $ 160,133 $ 168,348 $ 168,645 Net income 178,113 33,892 56,375 35,418 Net income attributable to Kilroy Realty Corporation 174,308 32,847 53,895 32,738 Preferred dividends and distributions (3,313 ) (3,312 ) (3,313 ) (3,312 ) Net income available to common stockholders 170,995 29,535 50,582 29,426 Net income available to common stockholders per share – basic 1.85 0.32 0.54 0.29 Net income available to common stockholders per share – diluted 1.84 0.31 0.54 0.29 ____________________ (1) The summation of the quarterly financial data may not equal the annual number reported on the consolidated statements of operations due to rounding. For the year ended December 31, 2016 , the summation of the quarterly net income available to common stockholders per share does not equal the annual number reported on the consolidated statements of operations due to the Company’s repurchase of common stock and its at-the-market stock offering programs that occurred during the year.

Quarterly Financial Informati39

Quarterly Financial Information of the Operating Partnership (Unaudited)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information of the Operating Partnership (Unaudited)	Quarterly Financial Information of the Company (Unaudited) Summarized quarterly financial data for the years ended December 31, 2017 and 2016 was as follows: 2017 Quarter Ended (1) March 31, June 30, September 30, December 31, (in thousands, except per share amounts) Revenues $ 179,308 $ 180,598 $ 181,534 $ 177,561 Net income 37,281 35,306 75,488 32,540 Net income attributable to Kilroy Realty Corporation 33,525 31,448 71,110 28,529 Total preferred dividends and distributions (7,196 ) (1,615 ) (4,552 ) — Net income available to common stockholders 26,329 29,833 66,558 28,529 Net income available to common stockholders per share – basic 0.27 0.30 0.67 0.28 Net income available to common stockholders per share – diluted 0.26 0.30 0.67 0.28 2016 Quarter Ended (1) March 31, June 30, September 30, December 31, (in thousands, except per share amounts) Revenues $ 145,446 $ 160,133 $ 168,348 $ 168,645 Net income 178,113 33,892 56,375 35,418 Net income attributable to Kilroy Realty Corporation 174,308 32,847 53,895 32,738 Preferred dividends and distributions (3,313 ) (3,312 ) (3,313 ) (3,312 ) Net income available to common stockholders 170,995 29,535 50,582 29,426 Net income available to common stockholders per share – basic 1.85 0.32 0.54 0.29 Net income available to common stockholders per share – diluted 1.84 0.31 0.54 0.29 ____________________ (1) The summation of the quarterly financial data may not equal the annual number reported on the consolidated statements of operations due to rounding. For the year ended December 31, 2016 , the summation of the quarterly net income available to common stockholders per share does not equal the annual number reported on the consolidated statements of operations due to the Company’s repurchase of common stock and its at-the-market stock offering programs that occurred during the year.
Kilroy Realty, L.P. [Member]
Quarterly Financial Information of the Operating Partnership (Unaudited)	Quarterly Financial Information of the Operating Partnership (Unaudited) Summarized quarterly financial data for the years ended December 31, 2017 and 2016 was as follows: 2017 Quarter Ended (1) March 31, June 30, September 30, December 31, (in thousands, except per unit amounts) Revenues $ 179,308 $ 180,598 $ 181,534 $ 177,561 Net income 37,281 35,306 75,488 32,540 Net income attributable to the Operating Partnership 34,054 31,971 72,402 29,013 Total preferred distributions (7,196 ) (1,615 ) (4,552 ) — Net income available to common unitholders 26,858 30,356 67,850 29,013 Net income available to common unitholders per unit – basic 0.26 0.30 0.67 0.28 Net income available to common unitholders per unit – diluted 0.26 0.30 0.67 0.28 2016 Quarter Ended (1) March 31, June 30, September 30, December 31, (in thousands, except per unit amounts) Revenues $ 145,446 $ 160,133 $ 168,348 $ 168,645 Net income 178,113 33,892 56,375 35,418 Net income attributable to the Operating Partnership 177,833 33,590 55,254 33,386 Preferred distributions (3,313 ) (3,312 ) (3,313 ) (3,312 ) Net income available to common unitholders 174,520 30,278 51,941 30,074 Net income available to common unitholders per unit – basic 1.85 0.31 0.54 0.29 Net income available to common unitholders per unit – diluted 1.84 0.31 0.54 0.29 ___________________ (1) The summation of the quarterly financial data may not equal the annual number reported on the consolidated statements of operations due to rounding. For the year ended December 31, 2016 , the summation of the quarterly net income available to common stockholders per share does not equal the annual number reported on the consolidated statements of operations due to the issuance of common units in connection with an acquisition, the Company’s repurchase of common stock and the its at-the-market stock offering programs that occurred during the year.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On January 12, 2018 , $43.4 million of dividends were paid out to common stockholders, common unitholders and RSU holders of record on December 29, 2017 . In January 2018, the Operating Partnership borrowed $75.0 million on the unsecured term loan facility. On January 29, 2018, the Executive Compensation Committee granted 56,015 RSUs to key employees under the 2006 Plan. The compensation cost related to the RSUs is expected to be recognized over a period of three years. On January 31, 2018, the Company completed the acquisition of three, two-story lab buildings encompassing 146,000 square feet for approximately $111.0 million in the Oyster Point submarket of South San Francisco.

Schedule II Valuation and Quali

Schedule II Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2017
Valuation and Qualifying Accounts [Abstract]
Schedule II - Valuation and Qualifying Accounts	Balance at Beginning of Period Charged to Costs and Expenses Recoveries (Deductions) Balance at End of Period (1) Allowance for Uncollectible Tenant Receivables for the year ended December 31, 2017 – Allowance for uncollectible tenant receivables $ 1,712 $ 1,517 $ (920 ) $ 2,309 2016 – Allowance for uncollectible tenant receivables 2,080 — (368 ) 1,712 2015 – Allowance for uncollectible tenant receivables 1,999 303 (222 ) 2,080 Allowance for Deferred Rent Receivables for the year ended December 31, 2017 – Allowance for deferred rent $ 1,524 $ 1,752 $ (38 ) $ 3,238 2016 – Allowance for deferred rent 1,882 — (358 ) 1,524 2015 – Allowance for deferred rent 1,989 242 (349 ) 1,882

Schedule III - Real Estate and

Schedule III - Real Estate and Accumulated Depreciation	12 Months Ended
	Dec. 31, 2017
SEC Schedule III, Real Estate and Accumulated Depreciation Disclosure [Abstract]
Schedule III - Real Estate and Accumulated Depreciation	The following table reconciles the historical cost of total real estate held for investment from January 1, 2015 to December 31, 2017 : Year Ended December 31, 2017 2016 2015 (in thousands) Total real estate held for investment, beginning of year $ 7,060,754 $ 6,328,146 $ 6,057,932 Additions during period: Acquisitions 19,829 460,957 139,123 Improvements, etc. 533,939 386,836 536,411 Total additions during period 553,768 847,793 675,534 Deductions during period: Cost of real estate sold (191,610 ) (68,200 ) (231,984 ) Properties held for sale — (13,193 ) (160,074 ) Other (5,135 ) (33,792 ) (13,262 ) Total deductions during period (196,745 ) (115,185 ) (405,320 ) Total real estate held for investment, end of year $ 7,417,777 $ 7,060,754 $ 6,328,146 The following table reconciles the accumulated depreciation from January 1, 2015 to December 31, 2017 : Year Ended December 31, 2017 2016 2015 (in thousands) Accumulated depreciation, beginning of year $ 1,139,853 $ 994,241 $ 947,664 Additions during period: Depreciation of real estate 190,515 171,983 159,524 Total additions during period 190,515 171,983 159,524 Deductions during period: Write-offs due to sale (66,206 ) (22,471 ) (66,603 ) Properties held for sale — (3,900 ) (46,191 ) Other — — (153 ) Total deductions during period (66,206 ) (26,371 ) (112,947 ) Accumulated depreciation, end of year $ 1,264,162 $ 1,139,853 $ 994,241

Basis of Presentation and Sig43

Basis of Presentation and Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Basis of presentation and significant accounting policies [Line Items]
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.
Partially Owned Entities and Variable Interest Entities	Effective January 1, 2016, the Company adopted FASB ASU No. 2015-02 (“ASU 2015-02”), which amended certain guidance with respect to the evaluation of Variable Interest Entities (“VIEs”) and when a reporting entity is required to consolidate certain legal entities. Specifically, the amendments: (i) modify the evaluation of whether limited partnerships and similar legal entities are VIEs or voting interest entities, (ii) eliminate the presumption that a general partner should consolidate a limited partnership, (iii) affect the consolidation analysis of reporting entities that are involved with VIEs, and (iv) provide a scope exception for certain entities. Under this guidance, effective January 1, 2016, the Operating Partnership was determined to be a VIE of the Company as the Operating Partnership is a limited partnership in which the common limited partners do not have substantive kick-out rights or participating rights. However, given that the Company was deemed to be the primary beneficiary of the Operating Partnership because the Company has the ability to control the activities that most significantly impact the Operating Partnership’s economic performance, the adoption of this new guidance and the conclusion that the Operating Partnership was a VIE did not have any impact on our consolidated financial statements since the conclusion to consolidate the Operating Partnership still applied. The Operating Partnership was the only new VIE identified as part of the adoption of the guidance as of January 1, 2016. At December 31, 2017 the consolidated financial statements of the Company included two VIEs in addition to the Operating Partnership: 100 First LLC and 303 Second LLC. At December 31, 2017 , the Company and the Operating Partnership were determined to be the primary beneficiaries of these two VIEs since we had the ability to control the activities that most significantly impact each of the VIEs’ economic performance. As of December 31, 2017 , the two VIEs’ total assets, liabilities and noncontrolling interests included on our consolidated balance sheet were 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. 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, 2016 , the consolidated financial statements of the Company included three VIEs in addition to the Operating Partnership: 100 First LLC, 303 Second LLC and entity established during the fourth quarter of 2016 to facilitate a transaction intended to qualify as a like-kind exchange pursuant to Section 1031 of the Code (“Section 1031 Exchange”). In January 2017, the Section 1031 Exchange was successfully completed and the entity established for the 1031 Exchange was no longer a VIE. At December 31, 2016 , the impact of consolidating the VIEs increased the Company’s total assets, liabilities and noncontrolling interests on our consolidated balance sheet by approximately $654.3 million (of which $588.6 million related to real estate held for investment on our consolidated balance sheet), approximately $166.1 million and approximately $124.3 million , respectively. The consolidated financial statements of the Operating Partnership included the same three VIEs at December 31, 2016 . Our accounting policy is to consolidate entities in which we have a controlling financial interest and significant decision making control over the entity's operations. In determining whether we have a controlling financial interest in a partially owned entity and the requirement to consolidate the accounts of that entity, we consider factors such as ownership interest, board representation, management representation, size of our investment (including loans), authority to control decisions, and contractual and substantive participating rights of the members. In addition to evaluating control rights, we consolidate entities in which the other members have no substantive kick-out rights to remove the Company as the managing member. Entities in which the equity investors do not have sufficient equity at risk to finance their endeavors without additional financial support or the holders of the equity investment at risk do not have a controlling financial interest are VIEs. We evaluate whether an entity is a VIE and whether we are the primary beneficiary. We are deemed to be the primary beneficiary of a VIE when we have the power to direct the activities of the VIE that most significantly impact the VIEs’ economic performance and the obligation to absorb losses or receive benefits that could potentially be significant to the VIE. If the requirements for consolidation are not met, the Company would account for investments under the equity method of accounting if we have the ability to exercise significant influence over the entity. Equity method investments would be initially recorded at cost and subsequently adjusted for our share of net income or loss and cash contributions and distributions each period. The Company did not have any equity method investments at December 31, 2017 or December 31, 2016 .
Acquisitions	Acquisitions Subsequent to our adoption of ASU No. 2017-01 on January 1, 2017, which was adopted on a prospective basis, acquisitions of operating properties and development and redevelopment opportunities generally no longer meet the definition of a business and are accounted for as asset acquisitions. For these asset acquisitions, we record the acquired tangible and intangible assets and assumed liabilities based on each asset’s and liability’s relative fair value at the acquisition date of the total purchase price plus any capitalized acquisition costs. We record the acquired tangible and intangible assets and assumed liabilities of acquisitions of operating properties and development and redevelopment opportunities that meet the accounting criteria to be accounted for as business combinations at fair value at the acquisition date. The acquired assets and assumed liabilities for an acquisition generally include but are not limited to (i) land and improvements, buildings and improvements, undeveloped land and construction in progress and (ii) identified tangible and intangible assets and liabilities associated with in-place leases, including tenant improvements, leasing costs, value of above-market and below-market operating leases and ground leases, acquired in-place lease values and tenant relationships, if any. Any debt assumed and equity (including common units of the Operating Partnership) issued in connection with a property acquisition is recorded at fair value on the date of acquisition. The fair value of land and improvements is derived from comparable sales of land and improvements within the same submarket and/or region. The fair value of buildings and improvements, tenant improvements and leasing costs considers the value of the property as if it was vacant as well as current replacement costs and other relevant market rate information. The fair value of the above-market or below-market component of an acquired in-place operating lease is based upon the present value (calculated using a market discount rate) of the difference between (i) the contractual rents to be paid pursuant to the lease over its remaining non-cancellable lease term and (ii) our estimate of the rents that would be paid using fair market rental rates and rent escalations at the date of acquisition measured over the remaining non-cancellable term of the lease for above-market operating leases and the initial non-cancellable term plus the term of any below-market fixed rate renewal options, if applicable, for below-market operating leases. Our below-market operating leases generally do not include fixed rate or below-market renewal options. The amounts recorded for above-market operating leases are included in deferred leasing costs and acquisition-related intangible assets, net on the balance sheet and are amortized on a straight-line basis as a reduction of rental income over the remaining term of the applicable leases. The amounts recorded for below-market operating leases are included in deferred revenue and acquisition-related intangible liabilities, net on the balance sheet and are amortized on a straight-line basis as an increase to rental income over the remaining term of the applicable leases plus the term of any below-market fixed rate renewal options, if applicable. The amortization of the below-market ground lease obligation is recorded as an increase to ground lease expense in the consolidated statements of operations for the periods presented. The amortization of the above-market ground lease obligation is recorded as a decrease to ground lease expense in the consolidations statements of operations for the periods presented. The fair value of acquired in-place leases is derived based on our assessment of lost revenue and costs incurred for the period required to lease the “assumed vacant” property to the occupancy level when purchased. The amount recorded for acquired in-place leases is included in deferred leasing costs and acquisition-related intangible assets, net on the balance sheet and amortized as an increase to depreciation and amortization expense over the remaining term of the applicable leases. Fully amortized intangible assets are written off each quarter. Subsequent to our adoption of “ASU 2017-01” on January 1, 2017, transaction costs associated with our acquisitions are capitalized as part of the purchase price of the acquisition. Prior to our adoption of “ASU 2017-01,” costs associated with all operating property acquisitions and those development and redevelopment acquisitions that met the criteria to be accounted for as business combinations were expensed as incurred and costs associated with development acquisitions accounted for as asset acquisitions were capitalized as part of the cost of the asset.
Operating Properties, Cost Capitalization, and Depreciations and Amortization of Buildings and Improvements	Operating Properties Operating properties are generally carried at historical cost less accumulated depreciation. Properties held for sale are reported at the lower of the carrying value or the fair value less estimated cost to sell. The cost of operating properties includes the purchase price or development costs of the properties. Costs incurred for the renovation and betterment of the operating properties are capitalized to our investment in that property. Maintenance and repairs are charged to expense as incurred. When evaluating properties to be held and used for potential impairment, we first evaluate whether there are any indicators of impairment for any of our properties. If any impairment indicators are present for a specific property, we then perform an undiscounted cash flow analysis and compare the net carrying amount of the property to the property’s estimated undiscounted future cash flow over the anticipated holding period. If the estimated undiscounted future cash flow is less than the net carrying amount of the property, we then perform an impairment loss calculation to determine if the fair value of the property is less than the net carrying value of the property. Our impairment loss calculation compares the net carrying amount of the property to the property’s estimated fair value, which may be based on estimated discounted future cash flow calculations or third-party valuations or appraisals. We would recognize an impairment loss if the asset’s net carrying amount exceeds the asset’s estimated fair value. If we were to recognize an impairment loss, the estimated fair value of the asset (less costs to sell for assets held for sale) would become its new cost basis. For a depreciable long-lived asset, the new cost basis would be depreciated (amortized) over the remaining useful life of that asset. Cost Capitalization All costs clearly associated with the development, redevelopment and construction of a property are capitalized as project costs, including internal compensation costs. In addition, the following costs are capitalized as project costs during periods in which activities necessary to prepare development and redevelopment properties for their intended use are in progress: pre-construction costs essential to the development of the property, interest, real estate taxes and insurance. • For office development and redevelopment properties that are pre-leased, we cease capitalization when revenue recognition commences, which is upon substantial completion of tenant improvements deemed to be the Company's asset for accounting purposes. • For office development and redevelopment properties that are not pre-leased, we may not immediately build out the tenant improvements. Therefore, we cease capitalization when revenue recognition commences upon substantial completion of the tenant improvements deemed to be the Company's asset for accounting purposes, but in any event, no later than one year after the cessation of major construction activities. We also cease capitalization on a development or redevelopment property when activities necessary to prepare the property for its intended use have been suspended. • For office development or redevelopment properties with multiple tenants and staged leasing, we cease capitalization and begin depreciation on the portion of the development or redevelopment property for which revenue recognition has commenced. • For residential development properties, we cease capitalization when the property is substantially complete and available for occupancy. Once major construction activity has ceased and the development or redevelopment property is in the lease-up phase, the costs capitalized to construction in progress are transferred to land and improvements, buildings and improvements, and deferred leasing costs on our consolidated balance sheets as the historical cost of the property. Depreciation and Amortization of Buildings and Improvements The costs of buildings and improvements and tenant improvements are depreciated using the straight-line method of accounting over the estimated useful lives set forth in the table below.
Discontinued Operations and Properties Held for Sale	Real Estate Assets Held for Sale, Dispositions and Discontinued Operations A real estate asset is classified as held for sale when certain criteria are met, including but not limited to the availability of the asset for immediate sale, the existence of an active program to locate a buyer and the probable sale or transfer of the asset within one year. If such criteria are met, we present the applicable assets and liabilities related to the real estate asset held for sale, if material, separately on the balance sheet and we would cease to record depreciation and amortization expense. Real estate assets held for sale are reported at the lower of their carrying value or their estimated fair value less the estimated costs to sell. As of December 31, 2017 , we did not have any properties classified as held for sale. As of December 31, 2016 , we classified one operating property located in San Diego, California as held for sale. Effective January 1, 2015, the Company adopted FASB ASU No. 2014-08 (“ASU 2014-08”), which changed the criteria for reporting discontinued operations while enhancing disclosures in this area. Under the guidance, only property disposals representing a strategic shift that has (or will have) a major effect on an entity’s operations and financial results, such as a major line of business, a major geographical area or a major equity investment, are required to be presented as discontinued operations. If we were to determine that the property disposition represents a strategic shift, the revenues, expenses and net gain (loss) on dispositions of the property would be recorded in discontinued operations for all periods presented through the date of the applicable disposition. The Company adopted and applied the new guidance on a prospective basis as required by ASU 2014-08. In accordance with this guidance, the operations of eleven , six and ten properties sold during the years ended December 31, 2017 , December 31, 2016 and December 31, 2015 , respectively, are presented in continuing operations as they did not represent a strategic shift in the Company’s operations and financial results. The net gains (losses) on dispositions of non-depreciable real estate property, including land, are reported in the consolidated statements of operations as gains (losses) on sale of land within continuing operations in the period the land is sold
Revenue Recognition, Tenant Reimbursements and Other Property Income	Revenue Recognition We recognize revenue from rent, tenant reimbursements, parking and other revenue once all of the following criteria are met: (i) the agreement has been fully executed and delivered, (ii) services have been rendered, (iii) the amount is fixed or determinable and (iv) the collectability of the amount is reasonably assured. Minimum annual rental revenues are recognized in rental revenues on a straight-line basis over the non-cancellable term of the related lease. Rental revenue recognition commences when the tenant takes possession or controls the physical use of the leased space. In order for the tenant to take possession, the leased space must be substantially complete and ready for its intended use. In order to determine whether the leased space is substantially ready for its intended use, we begin by determining whether the Company or the tenant owns the tenant improvements. When we conclude that the Company is the owner of tenant improvements, rental revenue recognition begins when the tenant takes possession of the finished space, which is generally when Company owned tenant improvements are substantially complete. In certain instances, when we conclude that the Company is not the owner (the tenant is the owner) of tenant improvements, rental revenue recognition begins when the tenant takes possession of or controls the space. When we conclude that the Company is the owner of tenant improvements, we record the cost to construct the tenant improvements, including costs paid for or reimbursed by the tenants, as a capital asset. For these tenant improvements, we record the amount funded by or reimbursed by the tenants as deferred revenue, which is amortized on a straight-line basis as additional rental income over the term of the related lease. When we conclude that the tenant is the owner of tenant improvements for accounting purposes, we record our contribution towards those improvements as a lease incentive, which is included in deferred leasing costs and acquisition-related intangible assets, net on our consolidated balance sheets and amortized as a reduction to rental income on a straight-line basis over the term of the lease. For residential properties, we commence revenue recognition upon occupancy of the units by the tenants. Residential rental revenue is recognized on a straight-line basis over the term of the related lease, net of any concessions. Tenant Reimbursements Reimbursements from tenants, consisting of amounts due from tenants for common area maintenance, real estate taxes and other recoverable costs, are recognized as revenue in the period the recoverable costs are incurred. Tenant reimbursements are recognized and recorded on a gross basis, as we are generally the primary obligor with respect to purchasing goods and services from third-party suppliers, have discretion in selecting the supplier, and have credit risk. Other Property Income Other property income primarily includes amounts recorded in connection with lease terminations, tenant bankruptcy settlement payments, broken deal income and property damage settlement related payments. Lease termination fees are amortized over the remaining lease term, if applicable. If there is no remaining lease term, they are recognized when received and realized. Other property income also includes miscellaneous income from tenants, such as fees related to the restoration of leased premises to their original condition and fees for late rental payments.
Allowances for Uncollectible Tenant and Deferred Rent Receivables	Allowances for Uncollectible Tenant and Deferred Rent Receivables We carry our current and deferred rent receivables net of allowances for uncollectible amounts. Our determination of the adequacy of these allowances is based primarily upon evaluations of individual receivables, current economic conditions, and other relevant factors. The allowances are increased or decreased through the provision for bad debts on our consolidated statements of operations.
Cash and Cash Equivalents	Cash and Cash Equivalents We consider all highly-liquid investments with original maturities of three months or less to be cash equivalents
Restricted Cash	Restricted Cash Restricted cash consists of cash proceeds from dispositions that are temporarily held at qualified intermediaries for purposes of facilitating potential Section 1031 Exchanges and cash held in escrow related to acquisition and disposition holdbacks. Restricted cash also includes cash held as collateral to provide credit enhancement for the Operating Partnership’s mortgage debt, including cash reserves for capital expenditures, tenant improvements and property taxes. As of December 31, 2017 , we did not have any restricted cash held at qualified intermediaries for the purpose of facilitating Section 1031 Exchanges. As of December 31, 2016 , we had $48.4 million restricted cash held at qualified intermediaries for the purpose of facilitating Section 1031 Exchanges. In January 2017, the Section 1031 Exchange was completed and the cash was released from the qualified intermediary.
Marketable Securities	Marketable Securities / Deferred Compensation Plan Marketable securities reported in our consolidated balance sheets represent the assets held in connection with the Kilroy Realty Corporation 2007 Deferred Compensation Plan (the “Deferred Compensation Plan”) (see Note 16 “Employee Benefit Plans” for additional information). The Deferred Compensation Plan assets are held in a limited rabbi trust and invested in various mutual and money market funds. As a result, the marketable securities are treated as trading securities for financial reporting purposes and are adjusted to fair value at the end of each accounting period, with the corresponding gains and losses recorded in interest income and other net investment gains.
Deferred Compensation Plan	At the time eligible management employees (“Participants”) defer compensation or earn mandatory Company contributions, or if we were to make a discretionary contribution, we record compensation cost and a corresponding deferred compensation plan liability, which is included in accounts payable, accrued expenses, and other liabilities on our consolidated balance sheets. This liability is adjusted to fair value at the end of each accounting period based on the performance of the benchmark funds selected by each Participant, and the impact of adjusting the liability to fair value is recorded as an increase or decrease to compensation cost. The impact of adjusting the deferred compensation plan liability to fair value and the changes in the value of the marketable securities held in connection with the Deferred Compensation Plan generally offset and therefore do not significantly impact net income.
Deferred Leasing Costs	Deferred Leasing Costs Costs incurred in connection with successful property leasing are capitalized as deferred leasing costs and classified as investing activities in the statement of cash flows. Deferred leasing costs consist primarily of leasing commissions and also include certain internal payroll costs and lease incentives, which are amortized using the straight-line method of accounting over the lives of the leases which generally range from one to 20 years. We reevaluate the remaining useful lives of leasing costs as the creditworthiness of our tenants and economic and market conditions change. If we determine that the estimated remaining life of a lease has changed, we adjust the amortization period accordingly. Fully amortized deferred leasing costs are written off each quarter.
Deferred Financing Costs, Debt Discounts and Premiums, Exchangeable Debt Instruments, and Gain and Losses on Early Extinguishment of Debt	Deferred Financing Costs Financing costs related to the origination or assumption of long-term debt are deferred and generally amortized using the straight-line method of accounting, which approximates the effective interest method, over the contractual terms of the applicable financings. Fully amortized deferred financing costs are written off when the corresponding financing is repaid. Debt Discounts and Premiums Original issuance debt discounts and discounts/premiums related to recording debt acquired in connection with operating property acquisitions at fair value are generally amortized and accreted on a straight-line basis, which approximates the effective interest method. Discounts are recorded as additional interest expense from date of issuance or acquisition through the contractual maturity date of the related debt. Premiums are recorded as a reduction to interest expense from the date of issuance or acquisition through the contractual maturity date of the related debt.
Noncontrolling Interest and Partnership Interests	Preferred Partnership Interests on the Operating Partnership’s Consolidated Balance Sheets Preferred partnership interests of the Operating Partnership as of December 31, 2016 represented the then issued and outstanding 4,000,000 6.875% Series G Cumulative Redeemable Preferred Units (“Series G Preferred Units”) and the 4,000,000 6.375% Series H Cumulative Redeemable Preferred Units (“Series H Preferred Units”). As of December 31, 2016 , the Series G and Series H Preferred Units were presented in the permanent equity section of the Operating Partnership’s consolidated balance sheets given that the Series G and Series H Preferred Units could only be redeemed at our option. The Company was the holder of both the Series G and Series H Preferred Units and for each Series G and Series H Preferred Unit the Company had an equivalent number of shares of the Company’s 6.875% Series G Cumulative Redeemable Preferred Stock (“Series G Preferred Stock”) and shares of the Company’s 6.375% Series H Cumulative Redeemable Preferred Stock (“Series H Preferred Stock”) publicly issued and outstanding. The Company redeemed all 4,000,000 shares of the Series G Preferred Stock and all 4,000,000 shares of the Series H Preferred Stock on March 30, 2017 and August 15, 2017 , respectively, resulting in the Operating Partnership redeeming the Series G and Series H Preferred Units on the same dates (see Note 14 “Preferred and Common Units of the Operating Partnership”). Noncontrolling Interests - Common Units of the Operating Partnership in the Company's Consolidated Financial Statements Common units of the Operating Partnership within noncontrolling interests in the Company’s consolidated financial statements represent the common limited partnership interests in the Operating Partnership not held by the Company (“noncontrolling common units”). Noncontrolling common units are presented in the equity section of the Company’s consolidated balance sheets and are reported at their proportionate share of the net assets of the Operating Partnership. Noncontrolling interests with redemption provisions that permit the issuer to settle in either cash or shares of common stock must be further evaluated to determine whether equity or temporary equity classification on the balance sheet is appropriate. Since the common units contain such a provision, we evaluated the accounting guidance and determined that the common units qualify for equity presentation in the Company’s consolidated financial statements. Net income attributable to noncontrolling common units is allocated based on their relative ownership percentage of the Operating Partnership during the reported period. The noncontrolling interest ownership percentage is determined by dividing the number of noncontrolling common units by the total number of common units outstanding. The issuance or redemption of additional shares of common stock or common units results in changes to the noncontrolling interest percentage as well as the total net assets of the Company. As a result, all equity transactions result in an allocation between equity and the noncontrolling interest in the Company’s consolidated balance sheets and statements of equity to account for the changes in the noncontrolling interest ownership percentage as well as the change in total net assets of the Company. Noncontrolling Interests in Consolidated Property Partnerships Noncontrolling interests in consolidated property partnerships represent the equity interests held by unrelated third parties in our three consolidated property partnerships (see Note 11 “Noncontrolling Interests on the Company’s Consolidated Financial Statements” and see Note 12 “Noncontrolling Interests on the Operating Partnership’s Consolidated Financial Statements”). Noncontrolling interests in consolidated property partnerships are not redeemable and are presented as permanent equity in the Company's consolidated balance sheets. We account for the noncontrolling interests in consolidated property partnerships using the hypothetical liquidation at book value (“HLBV”) method to attribute the earnings or losses of the consolidated property partnerships between the controlling and noncontrolling interests. Under the HLBV method, the amounts reported as noncontrolling interests in consolidated property partnerships in the consolidated balance sheets represent the amounts the noncontrolling interests would hypothetically receive at each balance sheet reporting date under the liquidation provisions of the governing agreements assuming the net assets of the consolidated property partnerships were liquidated at recorded amounts and distributed between the controlling and noncontrolling interests in accordance with the governing documents. The net income attributable to noncontrolling interests in consolidated property partnerships in the consolidated statements of operations is associated with the increase or decrease in the noncontrolling interest holders’ contractual claims on the respective entities’ balance sheets assuming a hypothetical liquidation at the end of that reporting period when compared with their claims on the respective entities’ balance sheets assuming a hypothetical liquidation at the beginning of that reporting period, after removing any contributions or distributions.
Equity Offerings	Equity Offerings Underwriting commissions and offering costs incurred in connection with common equity offerings and our at-the-market stock offering program (see Note 13 “Stockholders’ Equity of the Company”) are reflected as a reduction of additional paid-in capital. Issuance costs incurred in connection with preferred equity offerings are reflected as a reduction of the carrying value of the preferred equity. The Company records preferred stock issuance costs as a non-cash preferred equity distribution at the time we notify the holders of preferred stock or units of our intent to redeem such shares or units. Refer to Notes 13 “Stockholders’ Equity of the Company” and 14 “Partners’ Capital of the Operating Partnership” for details related to the redemption of the Series G and Series H Preferred Stock. The net proceeds from any equity offering of the Company are generally contributed to the Operating Partnership in exchange for a number of common or preferred units equivalent to the number of shares of common or preferred stock issued and are reflected in the Operating Partnership’s consolidated financial statements as an increase in partners’ capital.
Share-based Incentive Compensation Accounting	Share-based Incentive Compensation Accounting Compensation cost for all share-based awards, including options, requires measurement at estimated fair value on the grant date. Compensation cost is recognized on a straight-line basis over the service vesting period, which represents the requisite service period. The grant date fair value of market measure-based share-based compensation plans are calculated using a Monte Carlo simulation pricing model. The grant date fair value of stock option grants is calculated using the Black-Scholes valuation model. Equity awards settled in cash are valued at the fair value of our common stock on the period end date through the settlement date. Equity awards settled in cash are remeasured at each reporting period and are recognized as a liability in the consolidated balance sheet during the vesting period until settlement. Forfeitures of all share-based awards are recognized when they occur as forfeitures generally are not common or expected and have not historically been significant. For share-based awards in which the performance period precedes the grant date, we recognize compensation cost over the requisite service period, which includes both the performance and service vesting periods, using the accelerated attribution expense method. The requisite service period begins on the date the Executive Compensation Committee authorizes the award and adopts any relevant performance measures. For share-based awards with performance-based measures, the total estimated compensation cost is based on our most recent estimate of the probable achievement of the pre-established specific corporate performance measures. These estimates are based on our latest internal forecasts for each performance measure. For share-based awards with market measures, the total estimated compensation cost is based on the fair value of the award at the grant date. For share-based awards with performance-based measures and market measures, the total estimated compensation cost is based on the fair value per share at the grant date multiplied by our most recent estimate of the number of shares to be earned based on the probable achievement of the pre-established corporate performance measures based on our latest internal forecasts. In accordance with the provisions of our share-based incentive compensation plan, we accept the return of shares of Company common stock, at the current quoted market price, from employees to satisfy minimum statutory tax-withholding requirements related to shares that vested during the period. For share-based awards granted by the Company, the Operating Partnership issues a number of common units equal to the number of shares of common stock ultimately granted by the Company in respect of such awards.
Basic and Diluted Net Income (Loss)	Basic and Diluted Net Income Available to Common Stockholders per Share Basic net income available to common stockholders per share is computed by dividing net income available to common stockholders, after preferred distributions and the allocation of income to participating securities, by the weighted-average number of shares of common stock outstanding for the period. Diluted net income available to common stockholders per share is computed by dividing net income available for common stockholders, after preferred distributions and the allocation of income to participating securities, by the sum of the weighted-average number of shares of common stock outstanding for the period plus the assumed exercise of all dilutive securities. The impact of the outstanding common units is considered in the calculation of diluted net income available to common stockholders per share. The common units are not reflected in the diluted net income available to common stockholders per share calculation because the exchange of common units into common stock is on a one for one basis, and the common units are allocated net income on a per share basis equal to the common stock (see Note 20 “Net Income Available to Common Stockholders Per Share of the Company”). Accordingly, any exchange would not have any effect on diluted net income (loss) available to common stockholders per share. Nonvested share-based payment awards (including nonvested restricted stock units (“RSUs”), vested market-measure RSUs and vested dividend equivalents issued to holders of RSUs) containing nonforfeitable rights to dividends or dividend equivalents are accounted for as participating securities and included in the computation of basic and diluted net income available to common stockholders per share pursuant to the two-class method. The dilutive effect of stock options is reflected in the weighted average diluted outstanding shares calculation by application of the treasury stock method. The dilutive effect of the outstanding nonvested shares of common stock (“nonvested shares”) and RSUs that have not yet been granted but are contingently issuable under the share-based compensation programs is reflected in the weighted average diluted shares calculation by application of the treasury stock method at the beginning of the quarterly period in which all necessary conditions have been satisfied.
Fair Value Measurements	Fair Value Measurements The fair values of our financial assets and liabilities are disclosed in Note 19, “Fair Value Measurements and Disclosures,” to our consolidated financial statements. The only financial assets recorded at fair value on a recurring basis in our consolidated financial statements are our marketable securities. We elected not to apply the fair value option for any of our eligible financial instruments or other items. We determine the estimated fair value of financial assets and liabilities utilizing a hierarchy of valuation techniques based on whether the inputs to a fair value measurement are considered to be observable or unobservable in a marketplace. Observable inputs reflect market data obtained from independent sources, while unobservable inputs reflect our market assumptions. This hierarchy requires the use of observable market data when available. The following is the fair value hierarchy: • Level 1 – quoted prices for identical instruments in active markets; • Level 2 – quoted prices for similar instruments in active markets; quoted prices for identical or similar instruments in markets that are not active and model-derived valuations in which significant inputs and significant value drivers are observable in active markets; and • Level 3 – fair value measurements derived from valuation techniques in which one or more significant inputs or significant value drivers are unobservable. We determine the fair value for the marketable securities using quoted prices in active markets for identical assets. Our other financial instruments, which are only disclosed at fair value, are comprised of secured debt, unsecured senior notes, unsecured line of credit and unsecured term loan facility. We generally determine the fair value of our secured debt, unsecured debt, and unsecured line of credit by performing discounted cash flow analyses using an appropriate market discount rate. We calculate the market rate by obtaining period-end treasury rates for maturities that correspond to the maturities of our fixed-rate debt and then adding an appropriate credit spread based on information obtained from third-party financial institutions. These credit spreads take into account factors, including but not limited to, our credit profile, the tenure of the debt, amortization period, whether the debt is secured or unsecured, and the loan-to-value ratio of the debt to the collateral. These calculations are significantly affected by the assumptions used, including the discount rate, credit spreads and estimates of future cash flow. We calculate the market rate of our unsecured line of credit, unsecured term loan facility, and unsecured term loan by obtaining the period-end London Interbank Offered Rate (“LIBOR”) and then adding an appropriate credit spread based on our credit ratings, and the amended terms of our unsecured line of credit, unsecured term loan facility, and unsecured term loan agreement. We determine the fair value of each of our publicly traded unsecured senior notes based on their quoted trading price at the end of the reporting period, if such prices are available. Carrying amounts of our cash and cash equivalents, restricted cash and accounts payable approximate fair value due to their short-term maturities.
Income Taxes	Income Taxes We have elected to be taxed as a REIT under Sections 856 through 860 of the Code. To qualify as a REIT, we must distribute annually at least 90% of our adjusted taxable income, as defined in the Code, to our stockholders and satisfy certain other organizational and operating requirements. We generally will not be subject to federal income taxes if we distribute 100% of our taxable income for each year to our stockholders. If we fail to qualify as a REIT in any taxable year, we will be subject to federal income taxes (including any applicable alternative minimum tax) on our taxable income at regular corporate rates and we may not be able to qualify as a REIT for four subsequent taxable years. Even if we qualify for taxation as a REIT, we may be subject to certain state and local taxes on our income and property and to federal income taxes and excise taxes on our undistributed taxable income. We believe that we have met all of the REIT distribution and technical requirements for the years ended December 31, 2017 , 2016 and 2015 , and we were not subject to any federal income taxes (see Note 24 “Tax Treatment of Distributions” for additional information). We intend to continue to adhere to these requirements and maintain the Company’s REIT status. Accordingly, no provision for income taxes has been made in the accompanying financial statements. In addition, any taxable income from our taxable REIT subsidiary, which was formed in 2002, is subject to federal, state, and local income taxes. For the years ended December 31, 2017 , 2016 and 2015 the taxable REIT subsidiary had de minimis taxable income.
Uncertain Tax Positions	Uncertain Tax Positions We include favorable tax positions in the calculation of tax liabilities if it is more likely than not that our adopted tax position will prevail if challenged by tax authorities. We evaluated the potential impact of identified uncertain tax positions for all tax years still subject to audit under state and federal income tax law and concluded that we did not have any unrecognized tax benefits or any additional tax liabilities as of December 31, 2017 or 2016 . As of December 31, 2017 , the years still subject to audit are 2013 through 2017 under the California state income tax law and 2014 through 2017 under the federal income tax law.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reported periods. Actual results could differ from those estimates.
Segment	Segments We currently operate in one operating segment, our office properties segment.
Concentration of Credit Risk	Concentration of Credit Risk All of our properties and development and redevelopment projects are owned and all of our business is currently conducted in the state of California with the exception of the ownership and operation of twelve office properties and one development project under construction located in the state of Washington. The ability of tenants to honor the terms of their leases is dependent upon the economic, regulatory, and social factors affecting the communities in which our tenants operate. As of December 31, 2017 , our 15 largest tenants represented approximately 40.3% of total annualized base rental revenues, of which 5.0% was attributable to our largest tenant. We have deposited cash with financial institutions that is insured by the Federal Deposit Insurance Corporation (“FDIC”) up to $250,000 per institution. As of December 31, 2017 and 2016 , we had cash accounts in excess of FDIC insured limits.
Recent Accounting Pronouncements	Accounting Pronouncements Adopted January 1, 2018 Revenue From Contracts with Customers Effective January 1, 2018, we adopted 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. In connection with our long term project on this standard, 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 only sales of real estate and certain of our multi-tenant parking arrangements fall under the scope of Topic 606. Specifically, we evaluated the impact of the guidance on timing of gain recognition for dispositions and concluded there was no impact to our consolidated financial statements given the simplicity of the Company’s historical disposition transactions and no pending sales of real estate as of December 31, 2017. In addition, we also evaluated the impact of the guidance on the timing and pattern of revenue recognition for certain of our multi-tenant parking arrangements that fall under the scope of Topic 606 and determined there was no change in the timing or pattern of revenue recognition for such arrangements as compared to current accounting practice. Therefore we have concluded that adoption of the new revenue recognition guidance did not have an impact on our consolidated financial statements or notes to our consolidated financial statements. Other Pronouncements Adopted January 1, 2018 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 “Revenue From Contracts with Customers” 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 Accounting Standards Codification Subtopic 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. 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. The standard requires 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 standard requires 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 assets are the marketable securities related to our deferred compensation plan which are recorded as trading securities which are reported at fair value and marked to market through earnings each reporting period. Accounting Pronouncements Effective January 1, 2019 Leases 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 and early adoption is permitted. In January 2018, the FASB released an exposure draft to ASU No. 2016-02 that if issued in its current form 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 not be required to separate nonlease components from the associated lease components if certain conditions are met. 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 and the proposed exposure draft on our consolidated financial statements. For leases where we are the lessor, we currently believe that we would be able to elect the practical expedient proposed in the exposure draft and would not be required to separately bifurcate and report common area maintenance revenue for operating leases on our consolidated statements of operations. We also currently believe that such leases would be accounted for in a similar method to existing standards with the underlying leased asset being reported and recognized as a real estate asset. 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 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 December 31, 2017 , our future undiscounted minimum rental payments under these leases totaled $251.4 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 a financing type lease, 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. We currently expect to adopt ASU 2016-02 using the practical expedients proposed in the standard and the proposed exposure draft if issued in final form. Accounting Pronouncements Effective 2020 and Beyond 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.
Kilroy Realty, L.P. [Member]
Basis of presentation and significant accounting policies [Line Items]
Noncontrolling Interest and Partnership Interests	Common Partnership Interests on the Operating Partnership’s Consolidated Balance Sheets The common units held by the Company and the noncontrolling common units held by the common limited partners are both presented in the permanent equity section of the Operating Partnership’s consolidated balance sheets in partners’ capital. The redemption rights of the noncontrolling common units permit us to settle the redemption obligation in either cash or shares of the Company’s common stock at our option (see Note 11 “Noncontrolling Interests on the Company’s Consolidated Financial Statements” for additional information). Noncontrolling Interests on the Operating Partnership’s Consolidated Financial Statements Noncontrolling interests in the Operating Partnership’s consolidated financial statements include the noncontrolling interest in property partnerships (see Note 12 “Noncontrolling Interests on the Operating Partnership’s Consolidated Financial Statements”) and the Company’s 1.0% general partnership interest in the Finance Partnership. The 1.0% general partnership interest in the Finance Partnership noncontrolling interest is presented in the permanent equity section of the Operating Partnership’s consolidated balance sheets given that these interests are not convertible or redeemable into any other ownership interest of the Company or the Operating Partnership.
Basic and Diluted Net Income (Loss)	Basic and Diluted Net Income Available to Common Unitholders per Unit Basic net income available to common unitholders per unit is computed by dividing net income available to common unitholders, after preferred distributions and the allocation of income to participating securities, by the weighted-average number of vested common units outstanding for the period. Diluted net income available to common unitholders per unit is computed by dividing net income available to common unitholders, after preferred distributions and the allocation of income to participating securities, by the sum of the weighted-average number of common units outstanding for the period plus the assumed exercise of all dilutive securities. The dilutive effect of stock options, outstanding nonvested shares, RSUs, and awards containing nonforfeitable rights to dividend equivalents are reflected in diluted net income available to common unitholders per unit in the same manner as noted above for net income available to common stockholders per share.

Organization and Ownership (Tab

Organization and Ownership (Tables)	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of real estate properties	Our stabilized portfolio of operating properties was comprised of the following properties at December 31, 2017 : Number of Buildings Rentable Square Feet (unaudited) Number of Tenants Percentage Occupied (unaudited) Percentage Leased (unaudited) Stabilized Office Properties 101 13,720,597 511 95.2 % 96.9 % Number of Number of Units 2017 Average Occupancy Stabilized Residential Property 1 200 70.2 % Number of Properties/Projects Estimated Rentable Square Feet (unaudited) Development projects under construction (1)(2) 4 1,800,000 _______________ (1) Estimated rentable square feet upon completion. (2) Includes 86,000 square feet of Production, Distribution, and Repair (“PDR”) space. Development projects under construction also include 96,000 square feet of retail space and 237 residential units at One Paseo - Phase I in addition to the estimated office rentable square feet noted above.

Basis of Presentation and Sig45

Basis of Presentation and Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2017
Basis of Presentation and Significant Accounting Policies [Abstract]
Buildings, improvements, and tenant improvements depreciation	Asset Description Depreciable Lives Buildings and improvements 25 – 40 years Tenant improvements 1 – 20 years (1) ________________________ (1) Tenant improvements are amortized over the shorter of the lease term or the estimated useful life.

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Schedule of Acquisitions	During the year ended December 31, 2016 we acquired the seven operating properties listed below in three transactions with unrelated third parties. Property Date of Acquisition Number of Buildings Rentable Square Feet (unaudited) Occupancy as of December 31, 2016 (unaudited) Purchase Price (in millions) (1) 2016 Acquisitions 1290-1300 Terra Bella Avenue, Mountain View, CA (2) June 8, 2016 1 114,175 100.0% $ 55.4 8560-8590 West Sunset Blvd., West Hollywood, CA (3) December 7, 2016 4 178,699 87.5% 209.2 1701 Page Mill Rd. and 3150 Porter Dr., Palo Alto, CA (4) December 19, 2016 2 165,585 100.0% 130.0 Total (5) 7 458,459 $ 394.6 ________________________ (1) Excludes acquisition-related costs and non-lease related accrued liabilities assumed. Includes assumed unpaid leasing commissions and tenant improvements. (2) In connection with this acquisition, the Company assumed $0.2 million in accrued liabilities that are not included in the purchase price above. (3) This acquisition encompasses a 10-story office tower, three retail buildings, a four-level subterranean parking structure and three billboards. In connection with this acquisition, the Company assumed $0.1 million in accrued liabilities that are not included in the purchase price above. (4) In connection with this acquisition, the Company entered into a long-term ground lease expiring in December 2067. (5) The results of operations for the properties acquired during 2016 contributed $5.2 million and $1.7 million to revenue and net income from continuing operations, respectively, for the year ended December 31, 2016 .
Schedule of estimated fair values of the assets acquired and liabilities assumed	The following table summarizes the estimated fair values of the assets acquired and liabilities assumed at the respective acquisition dates for our 2016 operating property acquisitions: Acquisitions Total 2016 Acquisitions (1) Assets (in thousands) Land and improvements $ 120,110 Buildings and improvements (2) 259,301 Deferred leasing costs and acquisition-related intangible assets (3) 33,529 Total assets acquired 412,940 Liabilities Accounts payable, accrued expenses and other liabilities 1,122 Deferred revenue and acquisition-related intangible liabilities (4) 18,050 Total liabilities assumed 19,172 Net assets and liabilities acquired $ 393,768 _______________ (1) The purchase price of the three acquisitions completed during the year ended December 31, 2016 were individually less than 5% and in aggregate less than 10% of the Company’s total assets as of December 31, 2015 . (2) Represents buildings, building improvements and tenant improvements. (3) Represents in-place leases (approximately $27.1 million with a weighted average amortization period of 3.9 years), above-market leases (approximately $0.6 million with weighted average amortization period of 15.8 years) and leasing commissions (approximately $5.8 million with a weighted average amortization period of 5.1 years). (4) Represents below-market leases (approximately $18.1 million with a weighted average amortization period of 8.4 years)

Dispositions and Real Estate 47

Dispositions and Real Estate Assets Held for Sale (Tables)	12 Months Ended
	Dec. 31, 2017
Discontinued Operations and Disposal Groups [Abstract]
Schedule of operating property dispositions	The following table summarizes the operating properties sold during the years ended December 31, 2017 , 2016 and 2015 : Location Month of Disposition Number of Buildings Rentable Square Feet (unaudited) Sales Price (in millions) (1) 2017 Dispositions 5717 Pacific Center Boulevard, San Diego, CA (2) January 1 67,995 $ 12.1 Sorrento Mesa and Mission Valley Properties (3) September 10 675,143 174.5 Total 2017 Dispositions 11 743,138 $ 186.6 2016 Dispositions Torrey Santa Fe Properties (4) January 4 465,812 $ 262.3 4930, 4939 & 4955 Directors Place, San Diego, CA (5) July 2 136,908 49.0 Total 2016 Dispositions 6 602,720 $ 311.3 2015 Dispositions 15050 NE 36th Street, Redmond, WA April 1 122,103 $ 51.2 San Diego Properties - Tranches 1 and 2 (6) April/July 9 924,291 258.0 Total 2015 Dispositions 10 1,046,394 $ 309.2 __________________ (1) Represents gross sales price before the impact of broker commissions and closing costs. (2) This property was classified as held for sale at December 31, 2016 . (3) The Sorrento Mesa and Mission Valley Properties includes the following properties: 10390, 10394, 10398, 10421, 10445 and 10455 Pacific Center Court, 2355, 2365, 2375 and 2385 Northside Drive and Pacific Corporate Center - Lot 8, a 5.0 acre undeveloped land parcel. We recognized a gain on sale of land of $0.4 million related to the sale of Pacific Corporate Center - Lot 8 during the year ended December 31, 2017. (4) The Torrey Santa Fe Properties include the following properties: 7525, 7535, 7545 and 7555 Torrey Santa Fe. These properties were classified as held for sale at December 31, 2015 . (5) Includes two operating properties totaling 136,908 rentable square feet and a 7.0 acre undeveloped land parcel. (6) The San Diego Properties - Tranche 1 includes the following properties: 10770 Wateridge Circle, 6200 and 6220 Greenwich Drive. The San Diego Properties - Tranche 2 includes the following properties: 6260, 6290, 6310, 6340, 6350 Sequence Drive and 4921 Directors Place.
Schedule of operating properties and land held for sale	The major classes of assets and liabilities of the property held for sale as of December 31, 2016 were as follows: December 31, 2016 Real estate assets and other assets held for sale (in thousands) Land and improvements $ 2,693 Buildings and improvements 10,500 Total real estate held for sale 13,193 Accumulated depreciation and amortization (3,900 ) Total real estate held for sale, net 9,293 Prepaid expenses and other assets, net 124 Real estate and other assets held for sale, net $ 9,417 Liabilities of real estate assets held for sale Accounts payable, accrued expenses and other liabilities $ 56 Liabilities of real estate assets held for sale $ 56 We did not have any properties classified as held for sale as of December 31, 2017 . As of December 31, 2016 , the property listed below was classified as held for sale. Properties Submarket Property Type Number of Buildings Rentable Square Feet (unaudited) 2016 Held for Sale 5717 Pacific Center Drive (1) Sorrento Mesa Office 1 67,995 __________________ (1) In January 2017, the Company completed the sale of this property for a total sales price of $12.1 million as indicated on the table above.
Schedule of land dispositions	The following table summarizes the land dispositions completed during the years ended December 31, 2016 and 2015 : Properties Submarket Month of Disposition Gross Site Acreage (unaudited) Sales Price (1) (in millions) 2016 Land Dispositions Carlsbad Oaks - Lot 7 (2) Carlsbad January 7.6 $ 4.5 Carlsbad Oaks - Lots 4 & 5 Carlsbad June 11.2 6.0 Carlsbad Oaks - Lot 8 Carlsbad June 13.2 8.9 Total 2016 Land Dispositions (3)(4) 32.0 $ 19.4 2015 Land Disposition 17150 Von Karman (4) Irvine January 8.5 $ 26.0 __________________ (1) Represents gross sales price before the impact of commissions and closing costs. (2) This land parcel was classified as held for sale as of December 31, 2015. (3) In connection with these land dispositions, $2.3 million of secured debt was assumed by the buyers. (4) The 2016 land dispositions resulted in a net loss on sales of $0.3 million and the 2015 land disposition resulted in gain on sale of $17.3 million .

Deferred Leasing Costs and Ac48

Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, net (Tables)	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Summary of identified deferred leasing costs and acquisition-related intangible assets	The following table summarizes our deferred leasing costs and acquisition-related intangible assets (acquired value of leasing costs, above-market operating leases, in-place leases and below-market ground lease obligation) and intangible liabilities (acquired value of below-market operating leases and above-market ground lease obligation) as of December 31, 2017 and 2016 : December 31, 2017 December 31, 2016 (in thousands) Deferred Leasing Costs and Acquisition-related Intangible Assets, net: Deferred leasing costs $ 248,598 $ 239,958 Accumulated amortization (101,917 ) (89,633 ) Deferred leasing costs, net 146,681 150,325 Above-market operating leases 4,199 10,304 Accumulated amortization (3,068 ) (6,933 ) Above-market operating leases, net 1,131 3,371 In-place leases 82,097 94,813 Accumulated amortization (46,625 ) (40,593 ) In-place leases, net 35,472 54,220 Below-market ground lease obligation 490 490 Accumulated amortization (46 ) (38 ) Below-market ground lease obligation, net 444 452 Total deferred leasing costs and acquisition-related intangible assets, net $ 183,728 $ 208,368 Acquisition-related Intangible Liabilities, net: (1) Below-market operating leases $ 65,440 $ 69,472 Accumulated amortization (40,495 ) (33,689 ) Below-market operating leases, net 24,945 35,783 Above-market ground lease obligation 6,320 6,320 Accumulated amortization (626 ) (525 ) Above-market ground lease obligation, net 5,694 5,795 Total acquisition-related intangible liabilities, net $ 30,639 $ 41,578 _______________ (1) Included in deferred revenue and acquisition-related intangible liabilities, net in the consolidated balance sheets.
Amortization for the period related to deferred leasing costs and acquisition-related intangibles	The following table sets forth amortization related to deferred leasing costs and acquisition-related intangibles for the years ended December 31, 2017 , 2016 and 2015 . Year Ended December 31, 2017 2016 2015 (in thousands) Deferred leasing costs (1) $ 31,675 $ 28,639 $ 27,866 Above-market operating leases (2) 2,240 1,509 2,532 In-place leases (1) 18,650 11,676 14,622 Below-market ground lease obligation (3) 8 8 8 Below-market operating leases (4) (10,768 ) (8,674 ) (10,980 ) Above-market ground lease obligation (5) (101 ) (101 ) (101 ) Total $ 41,704 $ 33,057 $ 33,947 _______________ (1) The amortization of deferred leasing costs and in-place leases is recorded to depreciation and amortization expense and the amortization of lease incentives is recorded as a reduction to rental income in the consolidated statements of operations for the periods presented. (2) The amortization of above-market operating leases is recorded as a decrease to rental income in the consolidated statements of operations for the periods presented. (3) The amortization of the below-market ground lease obligation is recorded as an increase to ground lease expense in the consolidated statements of operations for the periods presented. (4) The amortization of below-market operating leases is recorded as an increase to rental income in the consolidated statements of operations for the periods presented. (5) The amortization of the above-market ground lease obligation is recorded as a decrease to ground lease expense in the consolidated statements of operations for the periods presented.
Estimated annual amortization related to deferred leasing costs and acquisition-related intangibles	The following table sets forth the estimated annual amortization expense related to deferred leasing costs and acquisition-related intangibles as of December 31, 2017 for future periods: Year Deferred Leasing Costs Above-Market Operating Leases (1) In-Place Leases Below-Market Ground Lease Obligation (2) Below-Market Operating Leases (3) Above-Market Ground Lease Obligation (4) (in thousands) 2018 $ 30,033 $ 395 $ 13,286 $ 8 $ (9,456 ) $ (101 ) 2019 25,501 207 8,850 8 (6,854 ) (101 ) 2020 20,085 53 5,610 8 (3,942 ) (101 ) 2021 16,048 53 2,508 8 (1,253 ) (101 ) 2022 13,332 40 1,708 8 (790 ) (101 ) Thereafter 41,682 383 3,510 404 (2,650 ) (5,189 ) Total $ 146,681 $ 1,131 $ 35,472 $ 444 $ (24,945 ) $ (5,694 ) _______________ (1) Represents estimated annual amortization related to above-market operating leases. Amounts will be recorded as a decrease to rental income in the consolidated statements of operations. (2) Represents estimated annual amortization related to below-market ground lease obligations. Amounts will be recorded as an increase to ground lease expense in the consolidated statements of operations. (3) Represents estimated annual amortization related to below-market operating leases. Amounts will be recorded as an increase to rental income in the consolidated statements of operations. (4) Represents estimated annual amortization related to above-market ground lease obligations. Amounts will be recorded as a decrease to ground lease expense in the consolidated statements of operations.

Receivables (Tables)

Receivables (Tables)	12 Months Ended
	Dec. 31, 2017
Receivables [Abstract]
Current Receivables, net	Current receivables, net is primarily comprised of contractual rents and other lease-related obligations due from tenants. The balance consisted of the following as of December 31, 2017 and 2016 : December 31, 2017 December 31, 2016 (in thousands) Current receivables $ 19,235 $ 15,172 Allowance for uncollectible tenant receivables (2,309 ) (1,712 ) Current receivables, net $ 16,926 $ 13,460
Deferred Rent Receivables, net	Deferred rent receivables, net consisted of the following as of December 31, 2017 and 2016 : December 31, 2017 December 31, 2016 (in thousands) Deferred rent receivables $ 249,629 $ 220,501 Allowance for deferred rent receivables (3,238 ) (1,524 ) Deferred rent receivables, net $ 246,391 $ 218,977

Prepaid Expenses and Other As50

Prepaid Expenses and Other Assets, Net (Tables)	12 Months Ended
	Dec. 31, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid expenses and other assets, net	Prepaid expenses and other assets, net consisted of the following at December 31, 2017 and 2016 : December 31, 2017 December 31, 2016 (in thousands) Furniture, fixtures and other long-lived assets, net $ 39,686 $ 40,395 Notes receivable (1) 19,912 19,439 Prepaid expenses & acquisition deposits 55,108 10,774 Total Prepaid Expenses and Other Assets, Net $ 114,706 $ 70,608 _______________ (1) Our notes receivables are held by two unrelated third parties. Approximately $15.1 million of our notes receivable balance was secured by real estate as of December 31, 2017 and 2016 .

Secured and Unsecured Debt of51

Secured and Unsecured Debt of the Operating Partnership (Tables) - Kilroy Realty, L.P. [Member]	12 Months Ended
	Dec. 31, 2017
Debt Instrument [Line Items]
Schedule of unsecured revolving credit facility	The following table summarizes the balance and terms of our unsecured revolving credit facility as of December 31, 2017 and 2016 : December 31, 2017 December 31, 2016 (in thousands) Outstanding borrowings $ — $ — Remaining borrowing capacity 750,000 600,000 Total borrowing capacity (1) $ 750,000 $ 600,000 Interest rate (2) 2.56 % 1.82 % Facility fee-annual rate (3) 0.200% Maturity date July 2022 July 2019 _______________ (1) As of December 31, 2017 , 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. As of December 31, 2016 , we had the option to borrow, subject to bank approval and obtaining commitments for any additional borrowing capacity, up to an additional $311.0 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% and LIBOR plus 1.050% as of December 31, 2017 and December 31, 2016 , respectively. (3) Our facility fee is paid on a quarterly basis and is calculated based on the total borrowing capacity. In addition to the facility fee, we incurred debt origination and legal costs. As of December 31, 2017 and 2016 , $6.0 million and $3.3 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 respective maturity date of our unsecured revolving credit facility,
Schedule of term loan facility	The following table summarizes the balance and terms of our unsecured term loan facility as of December 31, 2017 and 2016 : December 31, 2017 December 31, 2016 (in thousands) Outstanding borrowings (1) $ — $ 150,000 Remaining borrowing capacity 150,000 — Total borrowing capacity (2) $ 150,000 $ 150,000 Interest rate (3) 2.66 % 1.85 % Undrawn facility fee-annual rate (4) 0.200 % — % Maturity date July 2022 July 2019 _______________ (1) In July 2017, the unsecured term loan facility was paid down and the Facility was amended to include a 12-month delayed draw option (subject to a specified reduction in commitments unless 50% drawn within six months) on the unsecured term loan facility. The Company may draw on the unsecured term loan facility through July 2018, at which time the outstanding balance will become the balance of the unsecured term loan facility and no additional draws may be made. In January 2018, the Company borrowed $75.0 million under the unsecured term loan facility. (2) As of December 31, 2017 and December 31, 2016 , $1.2 million and $0.7 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% and LIBOR plus 1.150% as of December 31, 2017 and December 31, 2016 , respectively. (4) In July 2017, the Facility was amended to include a facility fee on the remaining borrowing capacity of the unsecured term loan facility, which is paid on a monthly basis.
Stated debt maturities and scheduled amortization payments, excluding debt discounts	The following table summarizes the stated debt maturities and scheduled amortization payments as of December 31, 2017 : Year (in thousands) 2018 $ 3,584 2019 76,309 2020 255,137 2021 5,342 2022 5,554 Thereafter 2,018,469 Total aggregate principal value (1) $ 2,364,395 ________________________ (1) Includes gross principal balance of outstanding debt before the effect of the following at December 31, 2017 : $13.6 million of unamortized deferred financing costs for the unsecured senior notes and secured debt, $6.3 million of unamortized discounts for the unsecured senior notes and $2.6 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 years ended December 31, 2017 , 2016 and 2015 . The interest expense capitalized was recorded as a cost of development and increased the carrying value of undeveloped land and construction in progress. Year Ended December 31, 2017 2016 2015 (in thousands) Gross interest expense $ 112,577 $ 105,263 $ 109,647 Capitalized interest and deferred financing costs (46,537 ) (49,460 ) (51,965 ) Interest expense $ 66,040 $ 55,803 $ 57,682
Secured debt [Member]
Debt Instrument [Line Items]
Debt balance and significant terms	The following table sets forth the composition of our secured debt as of December 31, 2017 and 2016 : Annual Stated Interest Rate (1) GAAP Effective Rate (1)(2) Maturity Date December 31, Type of Debt 2017 2016 (in thousands) Mortgage note payable 3.57% 3.57% December 2026 $ 170,000 $ 170,000 Mortgage note payable (3) 4.48% 4.48% July 2027 93,081 94,754 Mortgage note payable (3)(4) 6.05% 3.50% June 2019 78,894 82,443 Mortgage note payable (3)(5) 4.27% 4.27% February 2018 — 125,756 Mortgage note payable (6) 7.15% 7.15% May 2017 — 1,215 Total secured debt $ 341,975 $ 474,168 Unamortized Deferred Financing Costs (1,175 ) (1,396 ) Total secured debt, net $ 340,800 $ 472,772 ______________ (1) All interest rates presented are fixed-rate interest rates. (2) Represents the effective interest rate including the amortization of initial issuance discounts/premiums excluding the amortization of deferred financing costs. (3) The secured debt and the related properties that secure the debt are held in a special purpose entity and the properties are not available to satisfy the debts and other obligations of the Company or the Operating Partnership. (4) As of December 31, 2017 and 2016 , the mortgage loan had unamortized debt premiums of $2.6 million and $4.4 million , respectively. (5) This mortgage note payable, held by a consolidated property partnership, was repaid in November 2017 at par. NBREM contributed $54.4 million to fund their proportionate share of the payoff. Refer to Note 11 “Noncontrolling Interests on Company’s Consolidated Financial Statements” for additional information. (6) This mortgage note payable was repaid in February 2017 at par.
Unsecured senior notes [Member]
Debt Instrument [Line Items]
Debt balance and significant terms	The following table summarizes the balance and significant terms of the registered unsecured senior notes issued by the Operating Partnership and outstanding, which are presented net of unamortized discounts of $6.3 million and $6.6 million , as of December 31, 2017 and 2016 , respectively: Net Carrying Amount Issuance date Maturity date Stated coupon rate Effective interest rate (1) 2017 2016 (in thousands) 3.450% Unsecured Senior Notes (2) December 2017 December 2024 3.450% 3.471% $ 425,000 $ — Unamortized discount and deferred financing costs (4,047 ) — Net carrying amount $ 420,953 $ — 3.450% Unsecured Senior Notes (3) February 2017 February 2029 3.450% 3.450% $ 75,000 $ — Unamortized discount and deferred financing costs (475 ) — Net carrying amount $ 74,525 $ — 3.350% Unsecured Senior Notes (3) February 2017 February 2027 3.350% 3.350% $ 175,000 $ — Unamortized discount and deferred financing costs (1,056 ) — Net carrying amount $ 173,944 $ — 4.375% Unsecured Senior Notes (4) September 2015 October 2025 4.375% 4.444% $ 400,000 $ 400,000 Unamortized discount and deferred financing costs (4,292 ) (4,846 ) Net carrying amount $ 395,708 $ 395,154 4.250% Unsecured Senior Notes (5) July 2014 August 2029 4.250% 4.352% $ 400,000 $ 400,000 Unamortized discount and deferred financing costs (6,164 ) (6,696 ) Net carrying amount $ 393,836 $ 393,304 3.800% Unsecured Senior Notes (6) January 2013 January 2023 3.800% 3.804% $ 300,000 $ 300,000 Unamortized discount and deferred financing costs (1,382 ) (1,656 ) Net carrying amount $ 298,618 $ 298,344 4.800% Unsecured Senior Notes (6)(7) July 2011 July 2018 4.800% 4.827% $ — $ 325,000 Unamortized discount and deferred financing costs — (767 ) Net carrying amount $ — $ 324,233 6.625% Unsecured Senior Notes (8) May 2010 June 2020 6.625% 6.744% $ 250,000 $ 250,000 Unamortized discount and deferred financing costs (1,321 ) (1,868 ) Net carrying amount $ 248,679 $ 248,132 Total Unsecured Senior Notes, Net $ 2,006,263 $ 1,659,167 ________________________ (1) Represents the effective interest rate including the amortization of initial issuance discounts, excluding the amortization of deferred financing costs. (2) Interest on these notes is payable semi-annually in arrears on June 15th and December 15th of each year. (3) Interest on these notes is payable semi-annually in arrears on February 17th and August 17th of each year. (4) Interest on these notes is payable semi-annually in arrears on April 1st and October 1st of each year. (5) Interest on these notes is payable semi-annually in arrears on February 15th and August 15th of each year. (6) Interest on these notes is payable semi-annually in arrears on January 15th and July 15th of each year. (7) Certain common limited partners in the Operating Partnership that previously contributed their interests in the property at 6255 W. Sunset Blvd., Los Angeles, California to the Operating Partnership entered into an agreement with the Company. Pursuant to this agreement, such common limited partners will reimburse the Company for a portion of any amounts the Company may be required to pay pursuant to its guarantee of the Operating Partnership's 4.800% Senior Notes due 2018 or that the Company may otherwise become required to pay under applicable law with respect to such notes. These notes were redeemed by the Company in December 2017. (8) Interest on these notes is payable semi-annually in arrears on June 1st and December 1st of each year.

Deferred Revenue and Acquisit52

Deferred Revenue and Acquisition Related Liabilities, net (Tables)	12 Months Ended
	Dec. 31, 2017
Deferred Revenue Disclosure [Abstract]
Deferred revenue and acquisition-related liabilities	Deferred revenue and acquisition-related liabilities, net consisted of the following at December 31, 2017 and 2016 : December 31, 2017 2016 (in thousands) Deferred revenue related to tenant-funded tenant improvements $ 104,260 $ 99,489 Other deferred revenue 10,991 9,293 Acquisition-related intangible liabilities, net (1) 30,639 41,578 Total $ 145,890 $ 150,360 ________________________ (1) See Note 5 “Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, net” for additional information regarding our acquisition-related intangible liabilities.
Estimated amortization of deferred revenue related to tenant-funded improvements	The following is the estimated amortization of deferred revenue related to tenant-funded tenant improvements as of December 31, 2017 for the next five years and thereafter: Year Ending (in thousands) 2018 $ 16,644 2019 14,851 2020 14,062 2021 12,607 2022 11,458 Thereafter 34,638 Total $ 104,260

Stockholders' Equity of the C53

Stockholders' Equity of the Company (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Schedule of common stock sales under the at-the-market offering	The following table sets forth information regarding sales of our common stock under our at-the-market offering programs for the years ended December 31, 2017 , 2016 and 2015 : Year Ended December 31, 2017 2016 2015 (in millions, except share data) Shares of common stock sold during the period 235,077 451,398 1,866,267 Aggregate gross proceeds $ 17.7 $ 32.3 $ 140.1 Aggregate net proceeds after selling commissions $ 17.5 $ 31.9 $ 138.2
Schedule of accrued dividends and distributions	The following tables summarize accrued dividends and distributions for the noted outstanding shares of common stock, preferred stock, and noncontrolling units as of December 31, 2017 and 2016 : December 31, 2017 2016 (1) (in thousands) Dividends and Distributions payable to: Common stockholders $ 41,914 $ 212,074 Noncontrolling common unitholders of the Operating Partnership 883 5,418 RSU holders (2) 651 3,158 Total accrued dividends and distribution to common stockholders and noncontrolling unitholders 43,448 220,650 Preferred stockholders (3) — 1,656 Total accrued dividends and distributions $ 43,448 $ 222,306 ______________________ (1) Dividends and distributions payable to common stockholders, noncontrolling common unitholders of the Operating Partnership and RSU holders in 2016 include a special cash dividend of $1.90 per share that was declared by the Company’s Board of Directors on December 13, 2016. On January 13, 2017, the Company paid $184.3 million of special cash dividends to stockholders of record on December 30, 2016. This special dividend payment was in addition to the $36.4 million of regular dividends also paid on January 13, 2017 to common stockholders, unitholders and RSU holders of record on December 30, 2016. (2) The amount includes the value of the dividend equivalents that will be paid with additional RSUs (see Note 15 “Share-Based Compensation” for additional information). (3) The Series G and Series H Preferred stock were redeemed in March 2017 and August 2017, respectively, and the Company did not have any preferred stock outstanding as of December 31, 2017 .
Schedule of outstanding shares of common stock, preferred stock and noncontrolling units	December 31, 2017 2016 Outstanding Shares and Units: Common stock (1) 98,620,333 93,219,439 Noncontrolling common units 2,077,193 2,381,543 RSUs (2) 1,488,724 1,395,189 Series G Preferred stock (3) — 4,000,000 Series H Preferred stock (3) — 4,000,000 ______________________ (1) The amount includes nonvested shares. (2) The amount includes nonvested RSUs. Does not include 665,110 and 659,051 market measure-based RSUs because not all the necessary performance conditions have been met as of December 31, 2017 and 2016 , respectively. Refer to Note 15 “Share-Based Compensation” for additional information. (3) The Series G and Series H Preferred stock were redeemed in March 2017 and August 2017, respectively.

Preferred and Common Units of t

Preferred and Common Units of the Operating Partnership (Tables)	12 Months Ended
	Dec. 31, 2017
Class of Stock [Line Items]
Schedule of common stock sales under the at-the-market offering	The following table sets forth information regarding sales of our common stock under our at-the-market offering programs for the years ended December 31, 2017 , 2016 and 2015 : Year Ended December 31, 2017 2016 2015 (in millions, except share data) Shares of common stock sold during the period 235,077 451,398 1,866,267 Aggregate gross proceeds $ 17.7 $ 32.3 $ 140.1 Aggregate net proceeds after selling commissions $ 17.5 $ 31.9 $ 138.2
Redeemable noncontrolling interest	The following table sets forth the number of common units held by the Company and the number of common units held by non-affiliated investors and certain of our executive officers and directors in the form of noncontrolling common units as well as the ownership interest held on each respective date: December 31, 2017 December 31, 2016 Company owned common units in the Operating Partnership 98,620,333 93,219,439 Company owned general partnership interest 97.9 % 97.5 % Noncontrolling common units of the Operating Partnership 2,077,193 2,381,543 Ownership interest of noncontrolling interest 2.1 % 2.5 %
Schedule of accrued dividends and distributions	The following tables summarize accrued dividends and distributions for the noted outstanding shares of common stock, preferred stock, and noncontrolling units as of December 31, 2017 and 2016 : December 31, 2017 2016 (1) (in thousands) Dividends and Distributions payable to: Common stockholders $ 41,914 $ 212,074 Noncontrolling common unitholders of the Operating Partnership 883 5,418 RSU holders (2) 651 3,158 Total accrued dividends and distribution to common stockholders and noncontrolling unitholders 43,448 220,650 Preferred stockholders (3) — 1,656 Total accrued dividends and distributions $ 43,448 $ 222,306 ______________________ (1) Dividends and distributions payable to common stockholders, noncontrolling common unitholders of the Operating Partnership and RSU holders in 2016 include a special cash dividend of $1.90 per share that was declared by the Company’s Board of Directors on December 13, 2016. On January 13, 2017, the Company paid $184.3 million of special cash dividends to stockholders of record on December 30, 2016. This special dividend payment was in addition to the $36.4 million of regular dividends also paid on January 13, 2017 to common stockholders, unitholders and RSU holders of record on December 30, 2016. (2) The amount includes the value of the dividend equivalents that will be paid with additional RSUs (see Note 15 “Share-Based Compensation” for additional information). (3) The Series G and Series H Preferred stock were redeemed in March 2017 and August 2017, respectively, and the Company did not have any preferred stock outstanding as of December 31, 2017 .
Schedule of outstanding shares of common stock, preferred stock and noncontrolling units	December 31, 2017 2016 Outstanding Shares and Units: Common stock (1) 98,620,333 93,219,439 Noncontrolling common units 2,077,193 2,381,543 RSUs (2) 1,488,724 1,395,189 Series G Preferred stock (3) — 4,000,000 Series H Preferred stock (3) — 4,000,000 ______________________ (1) The amount includes nonvested shares. (2) The amount includes nonvested RSUs. Does not include 665,110 and 659,051 market measure-based RSUs because not all the necessary performance conditions have been met as of December 31, 2017 and 2016 , respectively. Refer to Note 15 “Share-Based Compensation” for additional information. (3) The Series G and Series H Preferred stock were redeemed in March 2017 and August 2017, respectively.
Kilroy Realty, L.P. [Member]
Class of Stock [Line Items]
Schedule of common stock sales under the at-the-market offering	During the years ended December 31, 2017 , 2016 and 2015 , the Company utilized its at-the-market stock offering programs to issue shares of common stock (see Note 13 “Stockholders’ Equity of the Company” for additional information). The net offering proceeds and property acquired using net offering proceeds were contributed by the Company to the Operating Partnership in exchange for common units for the years ended December 31, 2017 , 2016 and 2015 are as follows: Year Ended December 31, 2017 2016 2015 (in millions, except share and per share data) Shares of common stock contributed by the Company 235,077 451,398 1,866,267 Common units exchanged for shares of common stock by the Company 235,077 451,398 1,866,267 Aggregate gross proceeds $ 17.7 $ 32.3 $ 140.1 Aggregate net proceeds after selling commissions $ 17.5 $ 31.9 $ 138.2
Schedule of accrued dividends and distributions	The following tables summarize accrued distributions for the noted common and preferred units as of December 31, 2017 and 2016 : December 31, 2017 December 31, 2016 (1) (in thousands) Distributions payable to: General partner $ 41,914 $ 212,074 Common limited partners 883 5,418 RSU holders (2) 651 3,158 Total accrued distributions to common unitholders 43,448 220,650 Preferred unitholders (3) — 1,656 Total accrued distributions $ 43,448 $ 222,306 ______________________ (1) Distributions payable to the general partner, noncontrolling common unitholders of the Operating Partnership and RSU holders in 2016 include a special cash dividend of $1.90 per share that was declared by the Company’s Board of Directors on December 13, 2016. On January 13, 2017, the Company paid $184.3 million of special cash dividends to unitholders of record on December 30, 2016. This special dividend payment was in addition to the $36.4 million of regular dividends also paid on January 13, 2017 to common stockholders, unitholders and RSU holders of record on December 30, 2016. (2) The amount includes the value of the dividend equivalents that will be paid with additional RSUs (see Note 15 “Share-Based Compensation” for additional information).
Schedule of outstanding shares of common stock, preferred stock and noncontrolling units	December 31, 2017 December 31, 2016 Outstanding Units: Common units held by the general partner 98,620,333 93,219,439 Common units held by the limited partners 2,077,193 2,381,543 RSUs (1) 1,488,724 1,395,189 Series G Preferred units (2) — 4,000,000 Series H Preferred units (2) — 4,000,000 ______________________ (1) Does not include 665,110 and 659,051 market measure-based RSUs because not all the necessary performance conditions have been met as of December 31, 2017 and 2016 , respectively. Refer to Note 15 “Share-Based Compensation” for additional information. (2) The Series G and Series H Preferred units were redeemed in March 2017 and August 2017, respectively.

Share-Based Compensation (Table

Share-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of Restricted Stock Units Valuation Assumptions	As of December 31, 2017 , the estimated number of RSUs earned for the 2017 and 2016 Performance-Based RSUs and the actual number of RSUs earned for the 2015 Performance-Based RSUs was as follows: 2017 Performance-Based RSUs 2016 Performance-Based RSUs 2015 Performance-Based RSUs Service vesting period February 24, 2017 - January, 2020 January 28, 2016 - January, 2019 January 27, 2015 - January, 2018 Target RSUs granted 130,956 168,077 127,657 Estimated RSUs earned (1) 170,994 241,438 185,510 Date of valuation February 24, 2017 January 28, 2016 January 27, 2015 _______________ (1) Estimated RSUs earned for the 2017 Performance-Based RSUs are based on the actual achievement of the 2017 FFO Performance Condition and assumes target level achievement of the 2017 Market Condition and Other Performance Conditions. Estimated RSUs earned for the 2016 Performance-Based RSUs are based on the actual achievement of the 2016 FFO Performance Condition and assumes target level achievement of the 2016 Market Condition. The 2015 Performance-Based RSUs earned are based on actual performance of the 2015 FFO Performance Condition and the 2015 Market Condition. The total fair value of the Time-Based RSUs is based on the Company's closing share price on the NYSE on the respective fair valuation dates as detailed in the table below: 2017 Time-Based RSU Grant (1) 2016 Time-Based RSU Grant 2015 Time-Based RSU Grant Service vesting period February 2017 - January 5, 2020 January 28, 2016 - January 5, 2019 January 27, 2015 - January 5, 2018 Fair value on valuation date (in millions) $ 7.5 $ 7.1 $ 6.4 Fair value per share $ 73.30 $ 56.23 $ 75.34 Date of fair valuation February 2017 January 28, 2016 January 27, 2015 The following table summarizes the assumptions utilized in the Monte Carlo simulation pricing models: 2017 Award Fair Value Assumptions 2016 Award Fair Value Assumptions 2015 Award Fair Value Assumptions Valuation date February 24, 2017 January 28, 2016 January 27, 2015 Fair value per share on valuation date $80.89 $57.08 $75.34 Expected share price volatility 21.00% 26.00% 20.00% Risk-free interest rate 1.39% 1.13% 0.92% Expected life 2.8 years 2.9 years 2.9 years
Summary of Nonvested Restricted Stock	A summary of our nonvested restricted stock activity from January 1, 2017 through December 31, 2017 is presented below: Nonvested Weighted-Average Outstanding at January 1, 2017 36,535 $ 47.93 Transferred from time-based RSUs 10,610 60.16 Vested (1) (24,261 ) 46.39 Outstanding as of December 31, 2017 22,884 $ 55.23 _______________ (1) The total shares vested includes 10,792 shares that were tendered in accordance with the terms of the 2006 Plan to satisfy minimum statutory tax withholding requirements related to the restricted shares that have vested. We accept the return of shares at the current quoted closing share price of the Company’s common stock to satisfy tax withholding obligations
Summary of Nonvested and Vested Restricted Stock Activity	A summary of our nonvested and vested restricted stock activity for years ended December 31, 2017 , 2016 and 2015 is presented below: Shares Granted Shares Vested Years ended December 31, Nonvested Shares Issued Weighted-Average Grant Date Fair Value Per Share Vested Shares Total Fair Value at Vest Date (1) (in thousands) 2017 — $ — (24,261 ) $ 1,781 2016 — — (24,262 ) 1,527 2015 — — (24,264 ) 1,725 _______________ (1) Total fair value of shares vested was calculated based on the quoted closing share price of the Company’s common stock on the NYSE on the date of vesting.
Schedule of Stock Options Valuation Assumptions	The fair value of each stock option granted is estimated on the date of grant using the Black-Scholes option pricing model based on the following assumptions for the February 2012 Grant. February 2012 Option Grant Fair value of options granted per share $9.20 Expected stock price volatility 33.00% Risk-free interest rate 1.35% Dividend yield 3.80% Expected life of option 6.5 years
Summary of Stock Options Activity	A summary of our stock option activity related to the February 2012 grant from January 1, 2017 through December 31, 2017 is presented below: Number of Options Exercise Price Intrinsic Value (in millions) (1) Outstanding at December 31, 2016 314,500 $ 42.61 $ 9.6 Exercised (285,000 ) 42.61 8.8 Forfeited (3,000 ) 42.61 0.1 Outstanding at December 31, 2017 (2) 26,500 $ 42.61 $ 0.8 Options exercisable at December 31, 2017 (3) 26,500 $ 42.61 $ 0.8 _______________ (1) The intrinsic value of a stock option is the amount by which the fair value of the underlying stock exceeds the exercise price of an option. The fair value of the underlying stock was determined by using the closing share price on the NYSE on the date of exercise, forfeiture or respective period end. (2) As of December 31, 2017 , the average remaining life of stock options outstanding was 4.1 years. (3) As of December 31, 2017 , the average remaining life of stock options exercisable was approximately 4.1 years
Market measure-based Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Summary of Restricted Stock Units Award Activity	A summary of our performance and market-measure based RSU activity for years ended December 31, 2017 , 2016 and 2015 is presented below: RSUs Granted RSUs Vested Years ended December 31, Non-Vested RSUs Granted (1) Weighted-Average Fair Value Per Share (2) Vested RSUs Total Vest-Date Fair Value (in thousands) 2017 170,994 $ 78.97 (194,991 ) $ 14,270 2016 258,393 57.36 (36,914 ) 2,788 2015 191,483 79.25 — — _______________ (1) Non-vested RSUs granted during the years ended December 31, 2017 and 2016 are based on the actual achievement of the FFO performance conditions and assumes target level achievement for the market and other performance conditions. Non-vested RSUs granted during the year ended December 31, 2015 are based on the final performance of both the 2015 FFO performance and market conditions, and are non-vested as of December 31, 2017 as they are subject to the Compensation Committee’s confirmation of final performance. (2) Represents the grant-date fair value for all awards, excluding the 2014 Performance-Based RSU Grant, which was re-measured upon stockholder approval of the amended 2006 Plan on May 22, 2014, as an insufficient number of shares were available to settle these RSUs upon initial grant on January 29, 2014. A summary of our performance and market-measure based RSU activity from January 1, 2017 through December 31, 2017 is presented below: Nonvested RSUs Vested RSUs Total RSUs Amount Weighted-Average (1) Outstanding at January 1, 2017 659,051 $ 64.95 — 659,051 Granted 170,994 78.97 — 170,994 Vested (188,048 ) 64.93 188,048 — Settled (2) (136,191 ) (136,191 ) Issuance of dividend equivalents (3) 23,539 73.00 6,943 30,482 Forfeited (426 ) 78.55 (3,128 ) (3,554 ) Outstanding as of December 31, 2017 (4) 665,110 $ 68.83 55,672 720,782 _______________ (1) Represents the grant-date fair value for all awards, excluding the 2014 Performance-Based RSU Grant, which was re-measured upon stockholder approval of the amended 2006 Plan on May 22, 2014, as an insufficient number of shares were available to settle these RSUs upon initial grant on January 29, 2014. (2) Represents vested RSUs that were settled in shares of the Company’s common stock. Total shares settled include 72,938 shares that were tendered in accordance with the terms of the 2006 Plan to satisfy minimum statutory tax withholding requirements related to the RSUs settled. We accept the return of RSUs at the current quoted closing share price of the Company’s common stock to satisfy tax obligations. (3) Represents the issuance of dividend equivalents earned on the underlying RSUs. The dividend equivalents vest based on terms specified under the related RSU award agreement. (4) Outstanding RSUs as of December 31, 2017 represent the actual achievement of the FFO performance conditions and assumes target levels for the market and other performance conditions. The number of restricted stock units ultimately earned is subject to change based upon actual performance over the three-year vesting period. Dividend equivalents earned will vest along with the underlying award and are also subject to changes based on the number of RSUs ultimately earned for each underlying award.
Time-Based Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Summary of Restricted Stock Units Award Activity	A summary of our time-based RSU activity from January 1, 2017 through December 31, 2017 is presented below: Nonvested RSUs Vested RSUs Total RSUs Amount Weighted Average Fair Value (1) Outstanding at January 1, 2017 366,439 $ 59.07 1,028,750 1,395,189 Granted 142,101 74.91 — 142,101 Vested (172,731 ) 57.77 172,731 — Settled (2) (171,093 ) (171,093 ) Issuance of dividend equivalents (3) 8,601 73.00 55,364 63,965 Transferred to restricted stock (4) (10,610 ) 60.16 — (10,610 ) Forfeited (2,254 ) 63.27 — (2,254 ) Canceled (5) (4,824 ) (4,824 ) Outstanding as of December 31, 2017 331,546 $ 66.83 1,080,928 1,412,474 _______________ (1) Represents the grant-date fair value for all awards, excluding the 2014 Performance-Based RSU Grant, which was re-measured upon stockholder approval of the amended 2006 Plan on May 22, 2014, as an insufficient number of shares were available to settle these RSUs upon initial grant on January 29, 2014. (2) Represents vested RSUs that were settled in shares of the Company’s common stock. Total shares settled include 77,866 shares that were tendered in accordance with the terms of the 2006 Plan to satisfy minimum statutory tax withholding requirements related to the RSUs settled. We accept the return of RSUs at the current quoted closing share price of the Company’s common stock to satisfy tax obligations. (3) Represents the issuance of dividend equivalents earned on the underlying RSUs. The dividend equivalents vest based on terms specified under the related RSU award agreement. (4) During January 2017, RSUs were transferred to restricted stock based on the elected distribution date. (5) For shares vested but not yet settled, we accept the return of RSUs at the current quoted closing share price of the Company’s common stock to satisfy minimum statutory tax-withholding requirements related to either the settlement or vesting of RSUs in accordance with the terms of the 2006 Plan. A summary of our time-based RSU activity for the years ended December 31, 2017 , 2016 and 2015 is presented below: RSUs Granted RSUs Vested Year ended December 31, Non-Vested RSUs Issued Weighted-Average Grant Date Fair Value Per Share Vested RSUs Total Vest-Date Fair Value (1) (in thousands) 2017 142,101 $ 74.91 (228,095 ) $ 16,735 2016 173,747 58.29 (130,784 ) 8,438 2015 98,802 74.49 (107,541 ) 7,528 _______________ (1) Total fair value of RSUs vested was calculated based on the quoted closing share price of the Company’s common stock on the NYSE on the day of vesting. Excludes the issuance of dividend equivalents earned on the underlying RSUs. The dividend equivalents vest based on terms specified under the related RSU award agreement.

Future Minimum Rent (Tables)

Future Minimum Rent (Tables)	12 Months Ended
	Dec. 31, 2017
Leases [Abstract]
Future contractual minimum rent under operating lease	Future contractual minimum rent under operating leases as of December 31, 2017 for future periods is summarized as follows: Year Ending (in thousands) 2018 $ 555,393 2019 546,587 2020 525,637 2021 497,566 2022 476,146 Thereafter 2,569,163 Total (1) $ 5,170,492 The minimum commitment under our ground leases as of December 31, 2017 for five years and thereafter is as follows: Year Ending (in thousands) 2018 $ 4,957 2019 4,957 2020 4,957 2021 4,957 2022 4,957 Thereafter 226,633 Total (1)(2)(3)(4)(5) $ 251,418 ________________________ (1) Excludes contingent future rent payments based on gross income or adjusted gross income and reflects the minimum ground lease obligations before the impact of ground lease extension options. (2) One of our ground lease obligations is subject to a fair market value adjustment every five years ; however, the lease includes ground rent subprotection and infrastructure rent credits which currently limit our annual rental obligations to $1.0 million . The contractual obligations for that ground lease included above assumes the lesser of $1.0 million or annual lease rental obligation in effect as of December 31, 2017 . (3) One of our ground lease obligations includes a component which is based on the percentage of gross income that exceeds the minimum ground rent. The minimum rent is subject to increases every five years based on 50% of the average annual percentage rent for the previous five years. The contractual obligations for that lease included above assume the current annual ground lease obligation in effect at December 31, 2017 for the remainder of the lease term since we cannot predict future adjustments. (4) One of our ground lease obligations is subject to a fair market value adjustment every five years based on a combination of CPI adjustments and third-party appraisals limited to maximum increases annually. The contractual obligations for that lease included above assume the current annual ground lease obligation in effect at December 31, 2017 for the remainder of the lease term since we cannot predict future adjustments. (5) One of our ground lease obligations includes a component which is based on the percentage of adjusted gross income that exceeds the minimum ground rent. The minimum rent is subject to increases every 10 years by an amount equal to 60% of the average annual percentage rent for the previous three years.

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Schedule of contractual expiration dates for ground leases	The following table summarizes our properties that are held subject to long-term noncancellable ground lease obligations and the respective contractual expiration dates: Property Contractual Expiration Date (1) 601 108th Ave NE, Bellevue, WA November 2093 701, 801 and 837 N. 34th Street, Seattle, WA (2) December 2041 1701 Page Mill Road and 3150 Porter Drive, Palo Alto, CA December 2067 Kilroy Airport Center Phases I, II, and III, Long Beach, CA July 2084 ____________________ (1) Reflects the contractual expiration date prior to the impact of any extension or purchase options held by the Company. (2) The Company has three 10 -year and one 45 -year extension options for this ground lease, which if exercised would extend the expiration date to December 2116.
Schedule of future minimum rental repayments for ground leases	Future contractual minimum rent under operating leases as of December 31, 2017 for future periods is summarized as follows: Year Ending (in thousands) 2018 $ 555,393 2019 546,587 2020 525,637 2021 497,566 2022 476,146 Thereafter 2,569,163 Total (1) $ 5,170,492 The minimum commitment under our ground leases as of December 31, 2017 for five years and thereafter is as follows: Year Ending (in thousands) 2018 $ 4,957 2019 4,957 2020 4,957 2021 4,957 2022 4,957 Thereafter 226,633 Total (1)(2)(3)(4)(5) $ 251,418 ________________________ (1) Excludes contingent future rent payments based on gross income or adjusted gross income and reflects the minimum ground lease obligations before the impact of ground lease extension options. (2) One of our ground lease obligations is subject to a fair market value adjustment every five years ; however, the lease includes ground rent subprotection and infrastructure rent credits which currently limit our annual rental obligations to $1.0 million . The contractual obligations for that ground lease included above assumes the lesser of $1.0 million or annual lease rental obligation in effect as of December 31, 2017 . (3) One of our ground lease obligations includes a component which is based on the percentage of gross income that exceeds the minimum ground rent. The minimum rent is subject to increases every five years based on 50% of the average annual percentage rent for the previous five years. The contractual obligations for that lease included above assume the current annual ground lease obligation in effect at December 31, 2017 for the remainder of the lease term since we cannot predict future adjustments. (4) One of our ground lease obligations is subject to a fair market value adjustment every five years based on a combination of CPI adjustments and third-party appraisals limited to maximum increases annually. The contractual obligations for that lease included above assume the current annual ground lease obligation in effect at December 31, 2017 for the remainder of the lease term since we cannot predict future adjustments. (5) One of our ground lease obligations includes a component which is based on the percentage of adjusted gross income that exceeds the minimum ground rent. The minimum rent is subject to increases every 10 years by an amount equal to 60% of the average annual percentage rent for the previous three years.

Fair Value Measurements and D58

Fair Value Measurements and Disclosures (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair value of the company's marketable securities	The following table sets forth the fair value of our marketable securities as of December 31, 2017 and 2016 : Fair Value (Level 1) (1) 2017 2016 Description (in thousands) Marketable securities (2) $ 20,674 $ 14,773 _______________ (1) Based on quoted prices in active markets for identical securities. (2) The marketable securities are held in a limited rabbi trust .
Net gain (loss) on marketable securities	The following table sets forth the net gain (loss) on marketable securities recorded during the years ended December 31, 2017 , 2016 and 2015 : December 31, 2017 2016 2015 Description (in thousands) Net gain (loss) on marketable securities $ 3,023 $ 1,130 $ (269 )
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 December 31, 2017 and 2016 : December 31, 2017 2016 Carrying Value Fair Value (1) Carrying Value Fair Value (1) (in thousands) Liabilities Secured debt, net $ 340,800 $ 346,858 $ 472,772 $ 469,234 Unsecured debt, net 2,006,263 2,077,199 1,847,351 1,900,487 _______________ (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 Commo59

Net Income Available to Common Stockholders Per Share of the Company (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Net income available to common stockholders	The following table reconciles the numerator and denominator in computing the Company’s basic and diluted per-share computations for net income available to common stockholders for the years ended December 31, 2017 , 2016 and 2015 : Year Ended December 31, 2017 2016 2015 (in thousands, except unit and per unit amounts) Numerator: Net income attributable to Kilroy Realty Corporation $ 164,612 $ 293,788 $ 234,081 Total preferred dividends (13,363 ) (13,250 ) (13,250 ) Allocation to participating securities (1) (1,975 ) (3,839 ) (1,634 ) Numerator for basic and diluted net income available to common stockholders $ 149,274 $ 276,699 $ 219,197 Denominator: Basic weighted average vested shares outstanding 98,113,561 92,342,483 89,854,096 Effect of dilutive securities – contingently issuable shares and stock options 613,770 680,551 541,679 Diluted weighted average vested shares and common stock equivalents outstanding 98,727,331 93,023,034 90,395,775 Basic earnings per share: Net income available to common stockholders per share $ 1.52 $ 3.00 $ 2.44 Diluted earnings per share: Net income available to common stockholders per share $ 1.51 $ 2.97 $ 2.42 ________________________ (1) Participating securities include nonvested shares, certain time-based RSUs and vested market measure-based RSUs.

Net Income Available to Commo60

Net Income Available to Common Unitholders Per Unit of the Operating Partnership (Tables)	12 Months Ended
	Dec. 31, 2017
Net Income Available To Common Unitholders [Line Items]
Net income available to common unitholders	The following table reconciles the numerator and denominator in computing the Company’s basic and diluted per-share computations for net income available to common stockholders for the years ended December 31, 2017 , 2016 and 2015 : Year Ended December 31, 2017 2016 2015 (in thousands, except unit and per unit amounts) Numerator: Net income attributable to Kilroy Realty Corporation $ 164,612 $ 293,788 $ 234,081 Total preferred dividends (13,363 ) (13,250 ) (13,250 ) Allocation to participating securities (1) (1,975 ) (3,839 ) (1,634 ) Numerator for basic and diluted net income available to common stockholders $ 149,274 $ 276,699 $ 219,197 Denominator: Basic weighted average vested shares outstanding 98,113,561 92,342,483 89,854,096 Effect of dilutive securities – contingently issuable shares and stock options 613,770 680,551 541,679 Diluted weighted average vested shares and common stock equivalents outstanding 98,727,331 93,023,034 90,395,775 Basic earnings per share: Net income available to common stockholders per share $ 1.52 $ 3.00 $ 2.44 Diluted earnings per share: Net income available to common stockholders per share $ 1.51 $ 2.97 $ 2.42 ________________________ (1) Participating securities include nonvested shares, certain time-based RSUs and vested market measure-based RSUs.
Kilroy Realty, L.P. [Member]
Net Income Available To Common Unitholders [Line Items]
Net income available to common unitholders	The following table reconciles the numerator and denominator in computing the Operating Partnership’s basic and diluted per-unit computations for net income available to common unitholders for the years ended December 31, 2017 , 2016 and 2015 : Year Ended December 31, 2017 2016 2015 (in thousands, except unit and per unit amounts) Numerator: Net income attributable to Kilroy Realty, L.P. $ 167,440 $ 300,063 $ 238,137 Total preferred distributions (13,363 ) (13,250 ) (13,250 ) Allocation to participating securities (1) (1,975 ) (3,839 ) (1,634 ) Numerator for basic and diluted net income available to common unitholders $ 152,102 $ 282,974 $ 223,253 Denominator: Basic weighted average vested units outstanding 100,246,567 94,771,688 91,645,578 Effect of dilutive securities - contingently issuable shares and stock options 613,770 680,551 541,679 Diluted weighted average vested units and common unit equivalents outstanding 100,860,337 95,452,239 92,187,257 Basic earnings per unit: Net income available to common unitholders per unit $ 1.52 $ 2.99 $ 2.44 Diluted earnings per unit: Net income available to common unitholders per unit $ 1.51 $ 2.96 $ 2.42 ________________________ (1) Participating securities include nonvested shares, certain time-based RSUs and vested market measure-based RSUs.

Supplemental Cash Flow Inform61

Supplemental Cash Flow Information of the Company (Tables)	12 Months Ended
	Dec. 31, 2017
Supplemental Cash Flow Elements [Abstract]
Schedule of supplemental cash flows, company	Supplemental cash flow information follows (in thousands): Year Ended December 31, 2017 2016 2015 SUPPLEMENTAL CASH FLOWS INFORMATION: Cash paid for interest, net of capitalized interest of $44,757, $47,675, and $50,923 as of December 31, 2017, 2016 and 2015, respectively $ 67,336 $ 54,295 $ 54,747 NON-CASH INVESTING TRANSACTIONS: Accrual for expenditures for operating properties and development and redevelopment properties $ 116,089 $ 62,589 $ 109,715 Tenant improvements funded directly by tenants $ 15,314 $ 18,050 $ 13,387 Assumption of other assets and liabilities in connection with operating and development property acquisitions, net (Note 3) $ 1,443 $ 5,863 $ 6,254 Accrual for receivable related to development properties $ — $ 1,350 $ — Release of holdback funds to third party $ — $ — $ 9,279 NON-CASH FINANCING TRANSACTIONS: Accrual of dividends and distributions payable to common stockholders and common unitholders (Notes 13 and 27) $ 43,448 $ 220,650 $ 33,336 Accrual of dividends and distributions payable to preferred stockholders and preferred unitholders (Note 13) $ — $ 1,656 $ 1,656 Issuance of common units of the Operating Partnership in connection with an acquisition $ — $ 48,033 $ — Secured debt assumed by buyers in connection with land disposition (Note 4) $ — $ 2,322 $ — Exchange of common units of the Operating Partnership into shares of the Company’s common stock $ 10,939 $ 8,893 $ 1,223 Supplemental cash flow information follows (in thousands): Year Ended December 31, 2017 2016 2015 SUPPLEMENTAL CASH FLOWS INFORMATION: Cash paid for interest, net of capitalized interest of $44,757, $47,675, and $50,923 as of December 31, 2017, 2016 and 2015, respectively $ 67,336 $ 54,295 $ 54,747 NON-CASH INVESTING TRANSACTIONS: Accrual for expenditures for operating properties and development and redevelopment properties $ 116,089 $ 62,589 $ 109,715 Tenant improvements funded directly by tenants $ 15,314 $ 18,050 $ 13,387 Assumption of other assets and liabilities in connection with operating and development property acquisitions, net (Note 3) $ 1,443 $ 5,863 $ 6,254 Accrual for receivable related to development properties $ — $ 1,350 $ — Release of holdback funds to third party $ — $ — $ 9,279 NON-CASH FINANCING TRANSACTIONS: Accrual of dividends and distributions payable to common stockholders and common $ 43,448 $ 220,650 $ 33,336 Accrual of dividends and distributions payable to preferred stockholders and preferred unitholders (Note 14) $ — $ 1,656 $ 1,656 Issuance of common units in connection with a development property acquisition (Note 3) $ — $ 48,033 $ — Secured debt assumed by buyers in connection with land disposition (Note 4) $ — $ 2,322 $ —
Reconciliation of cash and cash equivalents and restricted cash	The following is a reconciliation of our cash and cash equivalents and restricted cash at the beginning and end of the years ended December 31, 2017 , 2016 and 2015 . Year Ended December 31, 2017 2016 2015 RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH: Cash and cash equivalents at beginning of period $ 193,418 $ 56,508 $ 23,781 Restricted cash at beginning of period 56,711 696 75,185 Cash and cash equivalents and restricted cash at beginning of period $ 250,129 $ 57,204 $ 98,966 Cash and cash equivalents at end of period $ 57,649 $ 193,418 $ 56,508 Restricted cash at end of period 9,149 56,711 696 Cash and cash equivalents and restricted cash at end of period $ 66,798 $ 250,129 $ 57,204

Supplemental Cash Flow Elements

Supplemental Cash Flow Elements (Tables)	12 Months Ended
	Dec. 31, 2017
Supplemental Cash Flow Elements [Abstract]
Schedule of supplemental cash flows, operating unit	Supplemental cash flow information follows (in thousands): Year Ended December 31, 2017 2016 2015 SUPPLEMENTAL CASH FLOWS INFORMATION: Cash paid for interest, net of capitalized interest of $44,757, $47,675, and $50,923 as of December 31, 2017, 2016 and 2015, respectively $ 67,336 $ 54,295 $ 54,747 NON-CASH INVESTING TRANSACTIONS: Accrual for expenditures for operating properties and development and redevelopment properties $ 116,089 $ 62,589 $ 109,715 Tenant improvements funded directly by tenants $ 15,314 $ 18,050 $ 13,387 Assumption of other assets and liabilities in connection with operating and development property acquisitions, net (Note 3) $ 1,443 $ 5,863 $ 6,254 Accrual for receivable related to development properties $ — $ 1,350 $ — Release of holdback funds to third party $ — $ — $ 9,279 NON-CASH FINANCING TRANSACTIONS: Accrual of dividends and distributions payable to common stockholders and common unitholders (Notes 13 and 27) $ 43,448 $ 220,650 $ 33,336 Accrual of dividends and distributions payable to preferred stockholders and preferred unitholders (Note 13) $ — $ 1,656 $ 1,656 Issuance of common units of the Operating Partnership in connection with an acquisition $ — $ 48,033 $ — Secured debt assumed by buyers in connection with land disposition (Note 4) $ — $ 2,322 $ — Exchange of common units of the Operating Partnership into shares of the Company’s common stock $ 10,939 $ 8,893 $ 1,223 Supplemental cash flow information follows (in thousands): Year Ended December 31, 2017 2016 2015 SUPPLEMENTAL CASH FLOWS INFORMATION: Cash paid for interest, net of capitalized interest of $44,757, $47,675, and $50,923 as of December 31, 2017, 2016 and 2015, respectively $ 67,336 $ 54,295 $ 54,747 NON-CASH INVESTING TRANSACTIONS: Accrual for expenditures for operating properties and development and redevelopment properties $ 116,089 $ 62,589 $ 109,715 Tenant improvements funded directly by tenants $ 15,314 $ 18,050 $ 13,387 Assumption of other assets and liabilities in connection with operating and development property acquisitions, net (Note 3) $ 1,443 $ 5,863 $ 6,254 Accrual for receivable related to development properties $ — $ 1,350 $ — Release of holdback funds to third party $ — $ — $ 9,279 NON-CASH FINANCING TRANSACTIONS: Accrual of dividends and distributions payable to common stockholders and common $ 43,448 $ 220,650 $ 33,336 Accrual of dividends and distributions payable to preferred stockholders and preferred unitholders (Note 14) $ — $ 1,656 $ 1,656 Issuance of common units in connection with a development property acquisition (Note 3) $ — $ 48,033 $ — Secured debt assumed by buyers in connection with land disposition (Note 4) $ — $ 2,322 $ —

Tax Treatment of Distributions

Tax Treatment of Distributions (Tables)	12 Months Ended
	Dec. 31, 2017
Class of Stock [Line Items]
Reconciliation of dividends declared to dividends paid	The following table reconciles the dividends declared per share of common stock to the dividends paid per share of common stock during the years ended December 31, 2017 , 2016 and 2015 as follows: Year Ended December 31, Dividends 2017 2016 2015 Dividends declared per share of common stock $ 1.650 $ 3.375 $ 1.400 Less: Dividends declared in the current year and paid in the following year (0.425 ) (2.275 ) (0.350 ) Add: Dividends declared in the prior year and paid in the current year (1) 2.275 0.350 0.350 Dividends paid per share of common stock $ 3.500 $ 1.450 $ 1.400 _________________ (1) The fourth quarter 2016 dividend of $2.275 per share of common stock consists of a special cash dividend of $1.90 per share of common stock and a regular quarterly cash dividend of $0.375 per share of common stock. The $1.90 per share special distribution is treated as paid in two tax years for income tax purposes: $1.587 is treated as paid on December 31, 2016 and $0.313 is treated as paid on January 13, 2017. The $0.375 per share regular quarterly distribution is considered a 2017 dividend distribution for income tax purposes.
Common stock [Member]
Class of Stock [Line Items]
Reconciliation of dividends declared to dividends paid	The unaudited income tax treatment for the dividends to common stockholders reportable for the years ended December 31, 2017 , 2016 and 2015 as identified in the table above was as follows: Year Ended December 31, Shares of Common Stock 2017 2016 2015 Ordinary income $ 1.356 70.87 % $ 1.500 49.40 % $ 0.992 70.86 % Qualified dividend 0.002 0.11 0.002 0.06 0.002 0.13 Return of capital 0.344 18.00 — — — — Capital gains (1) — — 1.212 39.89 0.051 3.65 Unrecaptured section 1250 gains 0.211 11.02 0.323 10.65 0.355 25.36 $ 1.913 100.00 % $ 3.037 100.00 % $ 1.400 100.00 % _________________ (1) Capital gains are comprised entirely of 20% rate gains.
Series G Preferred Stock [Member]
Class of Stock [Line Items]
Reconciliation of dividends declared to dividends paid	The 6.875% Series G Cumulative Redeemable Preferred Stock was issued in March 2012 and redeemed in March 2017. The unaudited income tax treatment for the dividends to Series G preferred stockholders reportable for the years ended December 31, 2017 , 2016 , and 2015 was as follows: Year Ended December 31, Preferred Shares 2017 2016 2015 Ordinary income $ 0.371 86.43 % $ 0.848 49.31 % $ 1.218 70.86 % Qualified dividend 0.001 0.14 0.001 0.06 0.002 0.13 Capital gains (1) — — 0.687 39.97 0.063 3.65 Unrecaptured section 1250 gains 0.058 13.43 0.183 10.66 0.436 25.36 $ 0.430 100.00 % $ 1.719 100.00 % $ 1.719 100.00 % __________________ (1) Capital gains are comprised entirely of 20% rate gains.
Series H Preferred Stock [Member]
Class of Stock [Line Items]
Reconciliation of dividends declared to dividends paid	The 6.375% Series H Cumulative Redeemable Preferred Stock was issued in August 2012 and redeemed in August 2017. The unaudited income tax treatment for the dividends to Series H preferred stockholders reportable for the years ended December 31, 2017 , 2016 , and 2015 was as follows: Year Ended December 31, Preferred Shares 2017 2016 2015 Ordinary income $ 1.033 86.43 % $ 0.786 49.31 % $ 1.129 70.86 % Qualified dividend 0.002 0.14 0.001 0.06 0.002 0.13 Capital gains (1) — — 0.637 39.97 0.059 3.65 Unrecaptured section 1250 gains 0.160 13.43 0.17 10.66 0.404 25.36 $ 1.195 100.00 % $ 1.594 100.00 % $ 1.594 100.00 % __________________ (1) Capital gains are comprised entirely of 20% rate gains.

Quarterly Financial Informati64

Quarterly Financial Information of the Company (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Schedule of summarized quarterly financial data	Summarized quarterly financial data for the years ended December 31, 2017 and 2016 was as follows: 2017 Quarter Ended (1) March 31, June 30, September 30, December 31, (in thousands, except per share amounts) Revenues $ 179,308 $ 180,598 $ 181,534 $ 177,561 Net income 37,281 35,306 75,488 32,540 Net income attributable to Kilroy Realty Corporation 33,525 31,448 71,110 28,529 Total preferred dividends and distributions (7,196 ) (1,615 ) (4,552 ) — Net income available to common stockholders 26,329 29,833 66,558 28,529 Net income available to common stockholders per share – basic 0.27 0.30 0.67 0.28 Net income available to common stockholders per share – diluted 0.26 0.30 0.67 0.28 2016 Quarter Ended (1) March 31, June 30, September 30, December 31, (in thousands, except per share amounts) Revenues $ 145,446 $ 160,133 $ 168,348 $ 168,645 Net income 178,113 33,892 56,375 35,418 Net income attributable to Kilroy Realty Corporation 174,308 32,847 53,895 32,738 Preferred dividends and distributions (3,313 ) (3,312 ) (3,313 ) (3,312 ) Net income available to common stockholders 170,995 29,535 50,582 29,426 Net income available to common stockholders per share – basic 1.85 0.32 0.54 0.29 Net income available to common stockholders per share – diluted 1.84 0.31 0.54 0.29 ____________________ (1) The summation of the quarterly financial data may not equal the annual number reported on the consolidated statements of operations due to rounding. For the year ended December 31, 2016 , the summation of the quarterly net income available to common stockholders per share does not equal the annual number reported on the consolidated statements of operations due to the Company’s repurchase of common stock and its at-the-market stock offering programs that occurred during the year.

Quarterly Financial Informati65

Quarterly Financial Information of the Operating Partnership (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2017
Schedule of summarized quarterly financial data	Summarized quarterly financial data for the years ended December 31, 2017 and 2016 was as follows: 2017 Quarter Ended (1) March 31, June 30, September 30, December 31, (in thousands, except per share amounts) Revenues $ 179,308 $ 180,598 $ 181,534 $ 177,561 Net income 37,281 35,306 75,488 32,540 Net income attributable to Kilroy Realty Corporation 33,525 31,448 71,110 28,529 Total preferred dividends and distributions (7,196 ) (1,615 ) (4,552 ) — Net income available to common stockholders 26,329 29,833 66,558 28,529 Net income available to common stockholders per share – basic 0.27 0.30 0.67 0.28 Net income available to common stockholders per share – diluted 0.26 0.30 0.67 0.28 2016 Quarter Ended (1) March 31, June 30, September 30, December 31, (in thousands, except per share amounts) Revenues $ 145,446 $ 160,133 $ 168,348 $ 168,645 Net income 178,113 33,892 56,375 35,418 Net income attributable to Kilroy Realty Corporation 174,308 32,847 53,895 32,738 Preferred dividends and distributions (3,313 ) (3,312 ) (3,313 ) (3,312 ) Net income available to common stockholders 170,995 29,535 50,582 29,426 Net income available to common stockholders per share – basic 1.85 0.32 0.54 0.29 Net income available to common stockholders per share – diluted 1.84 0.31 0.54 0.29 ____________________ (1) The summation of the quarterly financial data may not equal the annual number reported on the consolidated statements of operations due to rounding. For the year ended December 31, 2016 , the summation of the quarterly net income available to common stockholders per share does not equal the annual number reported on the consolidated statements of operations due to the Company’s repurchase of common stock and its at-the-market stock offering programs that occurred during the year.
Kilroy Realty, L.P. [Member]
Schedule of summarized quarterly financial data	Summarized quarterly financial data for the years ended December 31, 2017 and 2016 was as follows: 2017 Quarter Ended (1) March 31, June 30, September 30, December 31, (in thousands, except per unit amounts) Revenues $ 179,308 $ 180,598 $ 181,534 $ 177,561 Net income 37,281 35,306 75,488 32,540 Net income attributable to the Operating Partnership 34,054 31,971 72,402 29,013 Total preferred distributions (7,196 ) (1,615 ) (4,552 ) — Net income available to common unitholders 26,858 30,356 67,850 29,013 Net income available to common unitholders per unit – basic 0.26 0.30 0.67 0.28 Net income available to common unitholders per unit – diluted 0.26 0.30 0.67 0.28 2016 Quarter Ended (1) March 31, June 30, September 30, December 31, (in thousands, except per unit amounts) Revenues $ 145,446 $ 160,133 $ 168,348 $ 168,645 Net income 178,113 33,892 56,375 35,418 Net income attributable to the Operating Partnership 177,833 33,590 55,254 33,386 Preferred distributions (3,313 ) (3,312 ) (3,313 ) (3,312 ) Net income available to common unitholders 174,520 30,278 51,941 30,074 Net income available to common unitholders per unit – basic 1.85 0.31 0.54 0.29 Net income available to common unitholders per unit – diluted 1.84 0.31 0.54 0.29 ___________________ (1) The summation of the quarterly financial data may not equal the annual number reported on the consolidated statements of operations due to rounding. For the year ended December 31, 2016 , the summation of the quarterly net income available to common stockholders per share does not equal the annual number reported on the consolidated statements of operations due to the issuance of common units in connection with an acquisition, the Company’s repurchase of common stock and the its at-the-market stock offering programs that occurred during the year

Organization and Ownership (Det

Organization and Ownership (Details) - Dec. 31, 2017	Total	ft²	number_of_residential_units	project	tenant	building	property
Real Estate Properties [Line Items]
Rentable Square Feet (unaudited)		13,720,597
Office properties [Member]
Real Estate Properties [Line Items]
Number of buildings						101	4
Rentable Square Feet (unaudited)		13,720,597
Number of Tenants | tenant					511
Percentage Occupied (unaudited)	95.20%
Percentage Leased (unaudited)	96.90%
Stabilized residential properties [Member]
Real Estate Properties [Line Items]
Number of buildings | building						1
Percentage Occupied (unaudited)	70.20%
Number of units in real estate property | building						200
Development properties [Member]
Real Estate Properties [Line Items]
Number of buildings				4			3
Rentable Square Feet (unaudited)		1,800,000
Number of residential units | number_of_residential_units			237
Retail site [Member] | Development properties [Member]
Real Estate Properties [Line Items]
Rentable Square Feet (unaudited)		96,000
Retail site [Member] | Production, Distribution and Repair (PDR) [Member]
Real Estate Properties [Line Items]
Rentable Square Feet (unaudited)		86,000

Organization and Ownership (D67

Organization and Ownership (Details Textuals)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017ft²	Dec. 31, 2017project	Dec. 31, 2017building	Dec. 31, 2017a	Dec. 31, 2017property	Mar. 31, 2017ft²	Dec. 31, 2016
Real Estate Properties [Line Items]
Stabilized occupancy	95.00%
Rentable Square Feet (unaudited)		13,720,597
Percentage of general partnership interest owned by the company in the Operating Partnership	97.90%							97.50%
Ownership interest of noncontrolling interest	2.10%							2.50%
Kilroy Realty, L.P. [Member]
Real Estate Properties [Line Items]
Percentage of limited partnership interest owned by Operating Partnership	99.00%
101 First LLC and 303 Second LLC [Member]
Real Estate Properties [Line Items]
Percentage of general partnership interest owned by the company in the Operating Partnership	56.00%
Redwood LLC [Member]
Real Estate Properties [Line Items]
Percentage of general partnership interest owned by the company in the Operating Partnership	93.00%
Kilroy Realty Finance, Inc. [Member]
Real Estate Properties [Line Items]
Percentage of general partnership interest owned by wholly-owned subsidiary of the Company	1.00%
Washington [Member]
Real Estate Properties [Line Items]
Number of buildings | property						12
Washington - land parcel [Member]
Real Estate Properties [Line Items]
Number of buildings | building				1
Development properties [Member]
Real Estate Properties [Line Items]
Rentable Square Feet (unaudited)		1,800,000
Number of buildings			4			3
Development properties [Member] | Hollywood, California [Member]
Real Estate Properties [Line Items]
Rentable Square Feet (unaudited)							365,359
Development sites [Member]
Real Estate Properties [Line Items]
Number of buildings | project			6
Office properties [Member]
Real Estate Properties [Line Items]
Rentable Square Feet (unaudited)		13,720,597
Number of buildings				101		4
Area of land | a					48
Properties and Development Projects [Member]
Real Estate Properties [Line Items]
Property Ownership Percentage	100.00%

Basis of Presentation and Sig68

Basis of Presentation and Significant Accounting Policies (Details)	Aug. 15, 2017	Mar. 30, 2017	Jan. 31, 2015USD ($)	Mar. 31, 2012	Sep. 30, 2017	Dec. 31, 2017USD ($)tenantbuildingVIEpropertyshares	Dec. 31, 2016USD ($)buildingVIEpropertyshares	Dec. 31, 2015USD ($)property
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Net cash provided by (used in) investing activities						$ (359,102,000)	$ (579,420,000)	$ (337,241,000)
Increase (decrease) in restricted cash			$ (59,200,000)				56,000,000	(65,200,000)
Restricted cash						$ 0	$ 48,400,000
Number of VIEs | VIE						2	3
VIE asset amount						$ 426,500,000	$ 654,300,000
VIE, carrying amount, liabilities						27,300,000	166,100,000
Noncontrolling interest in consolidated subsidiary						181,575,000	130,732,000
Acquisition-related expenses						0	1,902,000	497,000
Depreciation of real estate						190,515,000	171,983,000	159,524,000
Initial premium on outstanding amount of secured debt						2,600,000
Original issuance costs of redeemed preferred units (Note 14)						$ 7,589,000	0	0
REIT annual taxable income distribution requirement percentage						90.00%
Company annual taxable income distribution						100.00%
Cash, FDIC insured amount						$ 250,000
Operating leases, future minimum payments receivable						251,400,000	5,170,492,000
Real estate investment [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
VIE asset amount						$ 382,100,000	588,600,000
VIE, carrying amount, liabilities							124,300,000
Properties held for sale [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of buildings | building						0
Minimum [Member] | Building and building improvements [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Property depreciable lives					25 years
Minimum [Member] | Leasehold improvements [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Property depreciable lives					1 year
Maximum [Member] | Building and building improvements [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Property depreciable lives					40 years
Maximum [Member] | Leasehold improvements [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Property depreciable lives					20 years
Lease Agreements [Member] | Minimum [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Finite-lived intangible asset, useful life						1 year
Lease Agreements [Member] | Maximum [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Finite-lived intangible asset, useful life						20 years
Kilroy Realty, L.P. [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Net cash provided by (used in) investing activities						$ (359,102,000)	(579,420,000)	(337,241,000)
Acquisition-related expenses						0	1,902,000	497,000
Original issuance costs of redeemed preferred units (Note 14)						7,589,000	0	0
100 First LLC & 303 Second LLC [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Noncontrolling interest in consolidated subsidiary						$ 175,400,000	124,300,000
Kilroy Realty Finance, Inc. [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Percentage of general partnership interest owned by wholly-owned subsidiary of the Company						1.00%
Secured debt [Member] | Kilroy Realty, L.P. [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Initial premium on outstanding amount of secured debt						$ 2,600,000
Unsecured debt [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Unamortized discount (premium), net						$ 6,300,000	$ 6,600,000
Series G Preferred Stock [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Preferred units, issued | shares						0	4,000,000
Preferred stock dividend rate (percentage)		6.875%		6.875%		0.00%	6.875%
Series H Preferred Stock [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Preferred units, issued | shares						0	4,000,000
Preferred stock dividend rate (percentage)	6.375%					0.00%	6.375%
Washington [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of buildings | property						12
Scenario, Previously Reported [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Net cash provided by (used in) investing activities							$ 635,400,000	$ 262,800,000
Customer Concentration Risk [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of tenants | tenant						15
Concentration risk, percentage						40.30%
Sales Revenue, Net [Member] | Customer Concentration Risk [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Concentration risk, percentage						5.00%
5717 Pacific Center Boulevard, San Diego, CA [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of buildings | property						1
5717 Pacific Center Boulevard, San Diego, CA [Member] | Properties held for sale [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of buildings | building							1
5717 Pacific Center Boulevard, San Diego, CA and Sorrento Mesa and Mission Valley Portfolio [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of buildings | property						11
Torrey Santa Fe Properties & 4930, 4939 & 4955 Directors Place, San Diego, CA [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of buildings | property							6
15050 NE 36th Street, Redmond, WA & San Diego Properties - Tranches 1 and 2 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of buildings | property								10
Accounting Standards Update 2016-18 [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Increase in Restricted Cash								$ 9,200,000

Acquisitions - 2016 Acquisition

Acquisitions - 2016 Acquisitions (Details) $ in Thousands	Dec. 19, 2016USD ($)ft²building	Dec. 07, 2016USD ($)ft²building	Jun. 08, 2016USD ($)ft²building	Dec. 31, 2016USD ($)ft²buildingproperty	Dec. 31, 2017ft²property
Business Acquisition [Line Items]
Number of operating properties acquired | property				7	0
Rentable Square Feet (unaudited) | ft²					13,720,597
Accounts payable, accrued expenses and other liabilities				$ 1,122
Revenue contributed from 2016 acquired properties				5,200
Net income contributed from 2016 acquired properties				$ 1,700
1290-1300 Terra Bella Avenue, Mountain View, CA [Member]
Business Acquisition [Line Items]
Number of Buildings | building			1
Rentable Square Feet (unaudited) | ft²			114,175
Occupancy as of December 31, 2016 (unaudited)				100.00%
Purchase Price (in millions) (1)			$ 55,400
Accounts payable, accrued expenses and other liabilities			$ 200
8560-8590 West Sunset Blvd., West Hollywood, CA [Member]
Business Acquisition [Line Items]
Number of Buildings | building		4
Rentable Square Feet (unaudited) | ft²		178,699
Occupancy as of December 31, 2016 (unaudited)				87.50%
Purchase Price (in millions) (1)		$ 209,200
Accounts payable, accrued expenses and other liabilities		$ 100
1701 Page Mill Rd. and 3150 Porter Dr., Palo Alto, CA [Member]
Business Acquisition [Line Items]
Number of Buildings | building	2
Rentable Square Feet (unaudited) | ft²	165,585
Occupancy as of December 31, 2016 (unaudited)				100.00%
Purchase Price (in millions) (1)	$ 130,000
Series of individually immaterial business acquisitions [Member]
Business Acquisition [Line Items]
Number of Buildings | building				7
Rentable Square Feet (unaudited) | ft²				458,459
Purchase Price (in millions) (1)				$ 394,600

Acquisitions - Estimated Fair V

Acquisitions - Estimated Fair Values (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)
Business Acquisition [Line Items]
Land and improvements	$ 120,110
Buildings and improvements (2)	259,301
Deferred leasing costs and acquisition-related intangible assets (3)	33,529
Total assets acquired	412,940
Accounts payable, accrued expenses and other liabilities	1,122
Deferred revenue and acquisition-related intangible liabilities (4)	18,050
Total liabilities assumed	19,172
Net assets and liabilities acquired	393,768
Below-market leases acquired	$ 18,100
Weighted average amortization period of below-market leases	8 years 4 months 24 days
In-place leases [Member]
Business Acquisition [Line Items]
Deferred leasing costs and acquisition-related intangible assets (3)	$ 27,100
Weighted average amortization period of above-market leases in years	3 years 10 months 24 days
Above market leases [Member]
Business Acquisition [Line Items]
Deferred leasing costs and acquisition-related intangible assets (3)	$ 600
Weighted average amortization period of above-market leases in years	15 years 9 months 18 days
Deferred leasing costs [Member]
Business Acquisition [Line Items]
Deferred leasing costs and acquisition-related intangible assets (3)	$ 5,800
Weighted average amortization period of above-market leases in years	5 years 1 month 6 days

Acquisitions - Development Proj

Acquisitions - Development Project Acquisitions and Acquisition Costs (Details) $ in Thousands	Oct. 10, 2017USD ($)a	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)ashares	Dec. 31, 2015USD ($)
Business Acquisition [Line Items]
Total liabilities assumed			$ 19,172
Acquisition costs, capitalized		$ 4,600	500	$ 1,100
Acquisition-related expenses		$ 0	$ 1,902	$ 497
Little Italy, Sand Diego, California [Member]
Business Acquisition [Line Items]
Area of land | a	1.20
Payments to acquire businesses	$ 19,400
Business acquisition, liabilities incurred	$ 1,400
Brannan St Project [Member]
Business Acquisition [Line Items]
Area of land | a			1.75
Payments to acquire businesses			$ 31,000
Business acquisition, equity interest issued or issuable, number of shares | shares			867,701
Business acquisition, equity interest issued or issuable, value assigned			$ 48,000
Business acquisition, transaction costs			2,400
Total liabilities assumed			$ 4,700

Dispositions and Real Estate 72

Dispositions and Real Estate Assets Held for Sale - Operating Property Dispositions (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)ft²property	Dec. 31, 2016USD ($)ft²aproperty	Dec. 31, 2015USD ($)ft²property
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rentable Square Feet (unaudited) | ft²	13,720,597
Gains on sales of depreciable operating properties | $	$ 39,507	$ 164,302	$ 109,950
5717 Pacific Center Boulevard, San Diego, CA [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of buildings | property	1
Rentable Square Feet (unaudited) | ft²	67,995
Proceeds from sale of property held-for-sale | $	$ 12,100
Sorrento Mesa and Mission Valley Portfolio [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of buildings | property	10
Rentable Square Feet (unaudited) | ft²	675,143
Proceeds from sale of property held-for-sale | $	$ 174,500
5717 Pacific Center Boulevard, San Diego, CA and Sorrento Mesa and Mission Valley Portfolio [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of buildings | property	11
Rentable Square Feet (unaudited) | ft²	743,138
Proceeds from sale of property held-for-sale | $	$ 186,600
Torrey Santa Fe Properties [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of buildings | property		4
Rentable Square Feet (unaudited) | ft²		465,812
Proceeds from sale of property held-for-sale | $		$ 262,300
4930, 4939 & 4955 Directors Place, San Diego, CA [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of buildings | property		2
Rentable Square Feet (unaudited) | ft²		136,908
Proceeds from sale of property held-for-sale | $		$ 49,000
Area of land | a		7
Torrey Santa Fe Properties & 4930, 4939 & 4955 Directors Place, San Diego, CA [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of buildings | property		6
Rentable Square Feet (unaudited) | ft²		602,720
Proceeds from sale of property held-for-sale | $		$ 311,300
15050 N.E. 36th St., Redmond, WA [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of buildings | property			1
Rentable Square Feet (unaudited) | ft²			122,103
Proceeds from sale of property held-for-sale | $			$ 51,200
San Diego Properties Tranches 1 & 2, San Diego, CA [Member] [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of buildings | property			9
Rentable Square Feet (unaudited) | ft²			924,291
Proceeds from sale of property held-for-sale | $			$ 258,000
15050 NE 36th Street, Redmond, WA & San Diego Properties - Tranches 1 and 2 [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of buildings | property			10
Rentable Square Feet (unaudited) | ft²			1,046,394
Proceeds from sale of property held-for-sale | $			$ 309,200

Dispositions and Real Estate 73

Dispositions and Real Estate Assets Held for Sale - Operating Properties Held for Sale (Details) $ in Millions	1 Months Ended
	Jan. 31, 2017USD ($)	Dec. 31, 2017ft²buildingproperty	Dec. 31, 2016ft²building
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rentable Square Feet (unaudited)		13,720,597
5717 Pacific Center Boulevard, San Diego, CA [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of buildings | property		1
Rentable Square Feet (unaudited)		67,995
Properties held for sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of buildings | building		0
Properties held for sale [Member] | 5717 Pacific Center Boulevard, San Diego, CA [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of buildings | building			1
Rentable Square Feet (unaudited)			67,995
Dispositions sales price | $	$ 12.1

Dispositions and Real Estate 74

Dispositions and Real Estate Assets Held for Sale - Operating Properties Held for Sale - Major Classes of Assets (Details) $ in Thousands	Dec. 31, 2016USD ($)
Land and land improvements [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Real estate held-for-sale	$ 2,693
Building and building improvements [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Real estate held-for-sale	10,500
Total real estate held for sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Real estate held-for-sale	13,193
Accumulated depreciation and amortization [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Real estate held-for-sale	3,900
Total real estate held for sale, net [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Real estate held-for-sale	9,293
Prepaid expenses and other current assets [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Real estate held-for-sale	124
Real estate and other assets held for sale, net [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Real estate held-for-sale	9,417
Accounts payable and accrued liabilities [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Real estate held-for-sale	56
Liabilities of real estate assets held for sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Real estate held-for-sale	$ 56

Dispositions and Real Estate 75

Dispositions and Real Estate Assets Held for Sale - Land Dispositions (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)a	Dec. 31, 2016USD ($)a	Dec. 31, 2015USD ($)a
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Secured debt assumed by buyers in connection with land disposition	$ 0	$ 2,322	$ 0
Net gain (loss) on sales of land (Note 4)	$ 449	$ (295)	17,116
Carlsbad Oaks - Lot 7 [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Area of land | a		7.6
Dispositions sales price		$ 4,500
Carlsbad Oaks - Lots 4 & 5 [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Area of land | a		11.2
Dispositions sales price		$ 6,000
Carlsbad Oaks - Lot 8 [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Area of land | a	5	13.2
Dispositions sales price		$ 8,900
Carlsbad Oaks - Lots 7, 4 & 5, 8 [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Area of land | a		32
Dispositions sales price		$ 19,400
Net gain (loss) on sales of land (Note 4)			$ 17,300
Von Karman, Irvine, California [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Area of land | a			8.5
Dispositions sales price			$ 26,000
Kilroy Realty, L.P. [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Secured debt assumed by buyers in connection with land disposition	$ 0	2,322	0
Net gain (loss) on sales of land (Note 4)	$ 449	$ (295)	$ 17,116

Dispositions and Real Estate 76

Dispositions and Real Estate Assets Held for Sale - Restricted Cash Related to Dispositions (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Discontinued Operations and Disposal Groups [Abstract]
Payments of debt extinguishment costs	$ 0
Restricted cash	$ 0	$ 48,400,000

Deferred Leasing Costs and Ac77

Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, net (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, Net
Total deferred leasing costs and acquisition-related intangible assets, net	$ 183,728	$ 208,368
Acquisition-related Intangible Liabilities, Net [Abstract]
Total acquisitions-related intangible liabilities, net	30,639	41,578
Deferred leasing costs [Member]
Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, Net
Finite-lived intangible assets/liabilities, gross	248,598	239,958
Accumulated amortization	(101,917)	(89,633)
Finite-lived intangible assets	146,681	150,325
Above market leases [Member]
Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, Net
Finite-lived intangible assets/liabilities, gross	4,199	10,304
Accumulated amortization	(3,068)	(6,933)
Finite-lived intangible assets	1,131	3,371
In-place leases [Member]
Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, Net
Finite-lived intangible assets/liabilities, gross	82,097	94,813
Accumulated amortization	(46,625)	(40,593)
Finite-lived intangible assets	35,472	54,220
Below-Market Ground Lease Obligation [Member]
Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, Net
Finite-lived intangible assets/liabilities, gross	490	490
Accumulated amortization	(46)	(38)
Finite-lived intangible assets	444	452
Below Market Operating Lease [Member]
Acquisition-related Intangible Liabilities, Net [Abstract]
Acquisition-related intangible liabilities, gross	65,440	69,472
Accumulated amortization	(40,495)	(33,689)
Acquisition-related intangible liabilities, net	24,945	35,783
Above-Market Ground Lease Obligation [Member]
Acquisition-related Intangible Liabilities, Net [Abstract]
Acquisition-related intangible liabilities, gross	6,320	6,320
Accumulated amortization	(626)	(525)
Acquisition-related intangible liabilities, net	$ 5,694	$ 5,795

Deferred Leasing Costs and Ac78

Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, net (Details 1) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Amortization for the period related to deferred leasing costs and acquisition-related intangibles
Amortization for the period related to deferred leasing costs and acquisition-related intangibles	$ 41,704	$ 33,057	$ 33,947
Deferred leasing costs [Member]
Amortization for the period related to deferred leasing costs and acquisition-related intangibles
Amortization for the period related to deferred leasing costs and acquisition-related intangibles	31,675	28,639	27,866
Estimated annual amortization related to acquisition-related intangibles
Finite-lived intangible assets, 2018	30,033
Finite-lived intangible assets, 2019	25,501
Finite-lived intangible assets, 2020	20,085
Finite-lived intangible assets, 2021	16,048
Finite-lived intangible assets, 2022	13,332
Finite-lived intangible assets, thereafter	41,682
Finite-lived intangible assets	146,681	150,325
Above market leases [Member]
Amortization for the period related to deferred leasing costs and acquisition-related intangibles
Amortization for the period related to deferred leasing costs and acquisition-related intangibles	2,240	1,509	2,532
Estimated annual amortization related to acquisition-related intangibles
Finite-lived intangible assets, 2018	395
Finite-lived intangible assets, 2019	207
Finite-lived intangible assets, 2020	53
Finite-lived intangible assets, 2021	53
Finite-lived intangible assets, 2022	40
Finite-lived intangible assets, thereafter	383
Finite-lived intangible assets	1,131	3,371
In-place leases [Member]
Amortization for the period related to deferred leasing costs and acquisition-related intangibles
Amortization for the period related to deferred leasing costs and acquisition-related intangibles	18,650	11,676	14,622
Estimated annual amortization related to acquisition-related intangibles
Finite-lived intangible assets, 2018	13,286
Finite-lived intangible assets, 2019	8,850
Finite-lived intangible assets, 2020	5,610
Finite-lived intangible assets, 2021	2,508
Finite-lived intangible assets, 2022	1,708
Finite-lived intangible assets, thereafter	3,510
Finite-lived intangible assets	35,472	54,220
Below-Market Ground Lease Obligation [Member]
Amortization for the period related to deferred leasing costs and acquisition-related intangibles
Amortization for the period related to deferred leasing costs and acquisition-related intangibles	8	8	8
Estimated annual amortization related to acquisition-related intangibles
Finite-lived intangible assets, 2018	8
Finite-lived intangible assets, 2019	8
Finite-lived intangible assets, 2020	8
Finite-lived intangible assets, 2021	8
Finite-lived intangible assets, 2022	8
Finite-lived intangible assets, thereafter	404
Finite-lived intangible assets	444	452
Below Market Operating Lease [Member]
Amortization for the period related to deferred leasing costs and acquisition-related intangibles
Amortization Of Intangible Liabilities	(10,768)	(8,674)	(10,980)
Estimated annual amortization related to acquisition-related intangibles
Acquisition-related intangible liabilities, 2018	(9,456)
Acquisition-related intangible liabilities, 2019	(6,854)
Acquisition-related intangible liabilities, 2020	(3,942)
Acquisition-related intangible liabilities, 2021	(1,253)
Acquisition-related intangible liabilities, 2022	(790)
Acquisition-related intangible liabilities, thereafter	(2,650)
Acquisition-related intangible liabilities	(24,945)	(35,783)
Above-Market Ground Lease Obligation [Member]
Amortization for the period related to deferred leasing costs and acquisition-related intangibles
Amortization Of Intangible Liabilities	(101)	(101)	$ (101)
Estimated annual amortization related to acquisition-related intangibles
Acquisition-related intangible liabilities, 2018	(101)
Acquisition-related intangible liabilities, 2019	(101)
Acquisition-related intangible liabilities, 2020	(101)
Acquisition-related intangible liabilities, 2021	(101)
Acquisition-related intangible liabilities, 2022	(101)
Acquisition-related intangible liabilities, thereafter	(5,189)
Acquisition-related intangible liabilities	$ (5,694)	$ (5,795)

Receivables (Details)

Receivables (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current Receivables, net
Current receivables	$ 19,235	$ 15,172
Allowance for uncollectible tenant receivables	(2,309)	(1,712)
Current receivables, net	16,926		$ 13,460
Deferred Rent Receivables, net
Deferred rent receivables	249,629	220,501
Allowance for deferred rent receivables	(3,238)	(1,524)
Deferred rent receivables, net	$ 246,391	$ 218,977

Prepaid Expenses and Other As80

Prepaid Expenses and Other Assets, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Furniture, fixtures and other long-lived assets, net	$ 39,686	$ 40,395
Notes receivable (1)	19,912	19,439
Prepaid expenses & acquisition deposits	55,108	10,774
Total Prepaid Expenses and Other Assets, Net	114,706	70,608
Secured debt [Member]
Debt Instrument [Line Items]
Notes receivable (1)	$ 15,100	$ 15,100

Secured and Unsecured Debt of81

Secured and Unsecured Debt of the Company (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Secured debt, net (Notes 8, 9 and 19)	$ 340,800,000	$ 472,772,000
Line of credit [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	150,000,000
Unsecured debt [Member]
Debt Instrument [Line Items]
Long-term debt	$ 2,000,000,000	$ 1,800,000,000

Secured and Unsecured Debt of82

Secured and Unsecured Debt of the Operating Partnership - Secured Debt (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Nov. 30, 2017	Aug. 30, 2016
Secured Debt
Secured debt, net (Notes 8, 9 and 19)	$ 340,800	$ 472,772
Amortization of debt issuance costs	(1,200)
Debt premium	2,600
Secured debt [Member]
Secured Debt
Amortization of debt issuance costs		(1,400)
Kilroy Realty, L.P. [Member]
Secured Debt
Long-term debt, gross	2,364,395
Secured debt, net (Notes 8, 9 and 19)	340,800	472,772
Kilroy Realty, L.P. [Member] | Secured debt [Member]
Secured Debt
Secured debt, net (Notes 8, 9 and 19)	341,975	474,168
Long-term debt	340,800	472,772
Debt premium	2,600
Net book value of properties pledged as collateral for secured debt	$ 338,200
Kilroy Realty, L.P. [Member] | Secured debt [Member] | 3.57% Mortgage Payable due December 2026 [Member]
Secured Debt
Stated interest rate	3.57%
Effective interest rate	3.57%
Maturity date	Dec. 1, 2026
Long-term debt, gross	$ 170,000	170,000
Kilroy Realty, L.P. [Member] | Secured debt [Member] | 4.48% Mortgage Payable due July 2027 [Member]
Secured Debt
Stated interest rate	4.48%
Effective interest rate	4.48%
Maturity date	Jul. 1, 2027
Long-term debt, gross	$ 93,081	94,754
Kilroy Realty, L.P. [Member] | Secured debt [Member] | 6.05% Mortgage Payable Due June 1, 2019 [Member]
Secured Debt
Stated interest rate	6.05%
Effective interest rate	3.50%
Maturity date	Jun. 1, 2019
Long-term debt, gross	$ 78,894	82,443
Debt premium	$ 2,600	4,400
Kilroy Realty, L.P. [Member] | Secured debt [Member] | 4.27% Mortgage Payable due Feb 1, 2018 [Member]
Secured Debt
Stated interest rate	4.27%
Effective interest rate	4.27%
Maturity date	Feb. 1, 2018
Long-term debt, gross	$ 0	125,756
Kilroy Realty, L.P. [Member] | Secured debt [Member] | 7.15% Mortgage Payable due May 1, 2017 [Member]
Secured Debt
Stated interest rate	7.15%
Effective interest rate	7.15%
Maturity date	May 1, 2017
Long-term debt, gross	$ 0	$ 1,215
Consolidated property partnerships [Member] | Third party [Member]
Secured Debt
Other ownership interests, contributed capital			$ 54,400	$ 452,900

Secured and Unsecured Debt of83

Secured and Unsecured Debt of the Operating Partnership Secured and Unsecured Debt of the Operating Partnership - Unsecured Senior Notes Table (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Outstanding borrowings (1)	$ 2,006,263	$ 1,847,351
Unsecured debt [Member]
Debt Instrument [Line Items]
Unamortized discount (premium), net	6,300	6,600
Kilroy Realty, L.P. [Member]
Debt Instrument [Line Items]
Long-term debt, gross	2,364,395
Outstanding borrowings (1)	2,006,263	1,847,351
Kilroy Realty, L.P. [Member] | Unsecured debt [Member]
Debt Instrument [Line Items]
Outstanding borrowings (1)	$ 2,006,263	1,659,167
Kilroy Realty, L.P. [Member] | Unsecured debt [Member] | 3.450% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Maturity date	Dec. 15, 2024
Stated interest rate	3.45%
Effective interest rate	3.471%
Long-term debt, gross	$ 425,000	0
Unamortized discount and deferred financing costs	4,047	0
Outstanding borrowings (1)	$ 420,953	0
Kilroy Realty, L.P. [Member] | Unsecured debt [Member] | 3.450% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Maturity date	Feb. 17, 2029
Stated interest rate	3.45%
Effective interest rate	3.45%
Long-term debt, gross	$ 75,000	0
Unamortized discount and deferred financing costs	(475)	0
Outstanding borrowings (1)	$ 74,525	0
Kilroy Realty, L.P. [Member] | Unsecured debt [Member] | 3.350% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Maturity date	Feb. 17, 2027
Stated interest rate	3.35%
Effective interest rate	3.35%
Long-term debt, gross	$ 175,000	0
Unamortized discount and deferred financing costs	(1,056)	0
Outstanding borrowings (1)	$ 173,944	0
Kilroy Realty, L.P. [Member] | Unsecured debt [Member] | 4.375% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Maturity date	Oct. 1, 2025
Stated interest rate	4.375%
Effective interest rate	4.444%
Long-term debt, gross	$ 400,000	400,000
Unamortized discount and deferred financing costs	4,292	4,846
Outstanding borrowings (1)	$ 395,708	395,154
Kilroy Realty, L.P. [Member] | Unsecured debt [Member] | 4.250% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Maturity date	Aug. 15, 2029
Stated interest rate	4.25%
Effective interest rate	4.352%
Long-term debt, gross	$ 400,000	400,000
Unamortized discount and deferred financing costs	(6,164)	6,696
Outstanding borrowings (1)	$ 393,836	393,304
Kilroy Realty, L.P. [Member] | Unsecured debt [Member] | 3.800% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Maturity date	Jan. 15, 2023
Stated interest rate	3.80%
Effective interest rate	3.804%
Long-term debt, gross	$ 300,000	300,000
Unamortized discount and deferred financing costs	(1,382)	1,656
Outstanding borrowings (1)	$ 298,618	298,344
Kilroy Realty, L.P. [Member] | Unsecured debt [Member] | 4.800% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Maturity date	Jul. 15, 2018
Stated interest rate	4.80%
Effective interest rate	4.827%
Long-term debt, gross	$ 0	325,000
Unamortized discount and deferred financing costs	0	767
Outstanding borrowings (1)	$ 0	324,233
Kilroy Realty, L.P. [Member] | Unsecured debt [Member] | 6.625% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Maturity date	Jun. 1, 2020
Stated interest rate	6.625%
Effective interest rate	6.744%
Long-term debt, gross	$ 250,000	250,000
Unamortized discount and deferred financing costs	1,321	(1,868)
Outstanding borrowings (1)	$ 248,679	$ 248,132

Secured and Unsecured Debt of84

Secured and Unsecured Debt of the Operating Partnership - Unsecured Senior Notes - Public Offerings and Private Placement (Details) - Kilroy Realty, L.P. [Member] - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Long-term debt, gross		$ 2,364,395
Unsecured debt [Member] | 3.450% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Long-term debt, gross		425,000	$ 0
Debt issuance cost		$ 600
Maturity date		Dec. 15, 2024
Stated interest rate		3.45%
Unsecured debt [Member] | 4.800% Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Long-term debt, gross		$ 0	$ 325,000
Maturity date		Jul. 15, 2018
Stated interest rate		4.80%
Extinguishment of Debt, Amount		$ 5,000
Write off of unamortized discount and deferred financing costs		300
Private placement [Member] | Unsecured debt [Member] | 3.35% Series A Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Long-term debt, gross		175,000
Private placement [Member] | Unsecured debt [Member] | 3.45% Series B Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Long-term debt, gross		$ 75,000
Private placement [Member] | Unsecured debt [Member] | Series A and B Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Operating partnership, payment percent	5.00%
Operating partnership, total payment percentage	100.00%

Secured and Unsecured Debt of85

Secured and Unsecured Debt of the Operating Partnership - Unsecured Revolving Credit Facility and Term Loan Facility (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Jan. 31, 2018	Dec. 31, 2015
Terms of Term Loan Facility
Outstanding borrowings (1)		$ 2,006,263,000	$ 1,847,351,000
Kilroy Realty, L.P. [Member]
Terms of the Credit Facility
Unamortized debt issuance expense		13,600,000
Terms of Term Loan Facility
Outstanding borrowings (1)		2,006,263,000	1,847,351,000
Revolving credit facility [Member] | Kilroy Realty, L.P. [Member]
Terms of the Credit Facility
Outstanding borrowings		0	0
Remaining borrowing capacity		750,000,000	600,000,000
Total borrowing capacity (1)		$ 750,000,000	$ 600,000,000
Interest rate (2)		2.56%	1.82%
Facility fee-annual rate (3)		0.20%	0.20%
Maturity date		Jul. 1, 2022	Jul. 1, 2019
Contingent additional borrowings		$ 600,000,000	$ 311,000,000
Unamortized debt issuance expense		6,000,000	3,300,000
Line of credit [Member]
Terms of the Credit Facility
Total borrowing capacity (1)		150,000,000
Line of credit [Member] | Kilroy Realty, L.P. [Member]
Terms of the Credit Facility
Outstanding borrowings		0	150,000,000
Remaining borrowing capacity		150,000,000	0
Total borrowing capacity (1)		$ 150,000,000	$ 150,000,000
Interest rate (2)		2.66%	1.85%
Facility fee-annual rate (3)		0.20%	0.00%
Maturity date		Jul. 1, 2022	Jul. 1, 2019
Delayed draw option, drawn down percent		50.00%
$150.0 million term loan facility [Member] | Line of credit [Member] | Kilroy Realty, L.P. [Member]
Terms of the Credit Facility
Unamortized debt issuance expense		$ 1,200,000	$ 700,000
$39 million unsecured term loan due July 2019 [Member] | Line of credit [Member] | Kilroy Realty, L.P. [Member]
Terms of the Credit Facility
Unamortized debt issuance expense			200,000
Terms of Term Loan Facility
Outstanding borrowings (1)			$ 39,000,000
London Interbank Offered Rate (LIBOR) [Member] | Kilroy Realty, L.P. [Member]
Terms of the Credit Facility
Basis spread on LIBOR			1.05%
London Interbank Offered Rate (LIBOR) [Member] | $150.0 million term loan facility [Member] | Revolving credit facility [Member] | Kilroy Realty, L.P. [Member]
Terms of the Credit Facility
Basis spread on LIBOR		1.00%
London Interbank Offered Rate (LIBOR) [Member] | $150.0 million term loan facility [Member] | Line of credit [Member] | Kilroy Realty, L.P. [Member]
Terms of the Credit Facility
Basis spread on LIBOR	1.10%
London Interbank Offered Rate (LIBOR) [Member] | $39 million unsecured term loan due July 2019 [Member] | Line of credit [Member] | Kilroy Realty, L.P. [Member]
Terms of the Credit Facility
Basis spread on LIBOR			1.15%
Unamortized debt issuance expense					$ 200,000
Subsequent event [Member] | Line of credit [Member] | Kilroy Realty, L.P. [Member]
Terms of the Credit Facility
Outstanding borrowings				$ 75,000,000
Terms of Term Loan Facility
Outstanding borrowings (1)				$ 75,000,000

Secured and Unsecured Debt of86

Secured and Unsecured Debt of the Operating Partnership - Debt Maturities (Details) $ in Thousands	Dec. 31, 2017USD ($)
Stated debt maturities and scheduled amortization payments, excluding debt discounts
Debt premium	$ 2,600
Kilroy Realty, L.P. [Member]
Stated debt maturities and scheduled amortization payments, excluding debt discounts
2,018	3,584
2,019	76,309
2,020	255,137
2,021	5,342
2,022	5,554
Thereafter	2,018,469
Total aggregate principal value (1)	2,364,395
Unamortized debt issuance expense	(13,600)
Unsecured senior notes [Member] | Kilroy Realty, L.P. [Member]
Stated debt maturities and scheduled amortization payments, excluding debt discounts
Unamortized discount	(6,300)
Secured debt [Member] | Kilroy Realty, L.P. [Member]
Stated debt maturities and scheduled amortization payments, excluding debt discounts
Debt premium	$ 2,600

Secured and Unsecured Debt of87

Secured and Unsecured Debt of the Operating Partnership - Capitalized Interest and Loan Fees (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Interest expense	$ 66,040	$ 55,803	$ 57,682
Kilroy Realty, L.P. [Member]
Debt Instrument [Line Items]
Gross interest expense	112,577	105,263	109,647
Capitalized interest and deferred financing costs	(46,537)	(49,460)	(51,965)
Interest expense	$ 66,040	$ 55,803	$ 57,682

Deferred Revenue and Acquisit88

Deferred Revenue and Acquisition Related Liabilities, net (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred Revenue Arrangement [Line Items]
Acquisition-related intangible liabilities, net	$ 30,639	$ 41,578
Deferred revenue and acquisition-related intangible liabilities, net	145,890	150,360
Tenant funded tenant improvements [Member]
Deferred Revenue Arrangement [Line Items]
Deferred revenue	104,260	99,489
Other deferred revenue [Member]
Deferred Revenue Arrangement [Line Items]
Deferred revenue	$ 10,991	$ 9,293

Deferred Revenue and Acquisit89

Deferred Revenue and Acquisition Related Liabilities, net (Details 2) - Tenant funded tenant improvements [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred Revenue Arrangement [Line Items]
Deferred revenues amortized and recognized as rental income	$ (16,800)	$ (13,200)	$ (13,300)
2,018	16,644
2,019	14,851
2,020	14,062
2,021	12,607
2,022	11,458
Thereafter	34,638
Deferred revenue	$ 104,260	$ 99,489

Noncontrolling Interests on t90

Noncontrolling Interests on the Company's Consolidated Financial Statements (Details)	12 Months Ended
	Dec. 31, 2016USD ($)shares	Dec. 31, 2015USD ($)	Dec. 31, 2017USD ($)$ / sharesshares	Nov. 30, 2017USD ($)	Nov. 30, 2016USD ($)	Aug. 30, 2016USD ($)ft²property	Mar. 31, 2016$ / shares
Noncontrolling Interest [Line Items]
Percentage of general partnership interest owned by the company in the Operating Partnership	97.50%		97.90%
Ownership interest of noncontrolling interest	2.50%		2.10%
Aggregate value upon redemption of outstanding noncontrolling common units	$ 174,900,000		$ 154,500,000
Contribution by noncontrolling interest in consolidated property partnership	453,449,000	$ 474,000
Noncontrolling interest in consolidated subsidiary	130,732,000		181,575,000
Kilroy Realty, L.P. [Member]
Noncontrolling Interest [Line Items]
Contribution by noncontrolling interest in consolidated property partnership	(3,615,000)
100 First LLC & 303 Second LLC [Member]
Noncontrolling Interest [Line Items]
Noncontrolling interest in consolidated subsidiary	124,300,000		$ 175,400,000
Redwood LLC [Member]
Noncontrolling Interest [Line Items]
Percentage of general partnership interest owned by the company in the Operating Partnership			93.00%
Noncontrolling interest in consolidated subsidiary	$ 6,400,000		$ 6,200,000
Capital units [Member] | Kilroy Realty, L.P. [Member]
Noncontrolling Interest [Line Items]
Noncontrolling common units | shares	2,381,543		2,077,193
Brannan St Project [Member]
Noncontrolling Interest [Line Items]
Common stock, par value | $ / shares			$ 0.01				$ 0.01
Consolidated property partnerships [Member]
Noncontrolling Interest [Line Items]
Real estate investments, joint ventures						$ 1,200,000,000
Consolidated property partnerships [Member] | Third party [Member]
Noncontrolling Interest [Line Items]
Percentage of general partnership interest owned by the company in the Operating Partnership						44.00%
Ownership interest of noncontrolling interest						44.00%
Number of buildings | property						2
Real estate investments, joint ventures						$ 1,200,000,000
Other ownership interests, contributed capital				$ 54,400,000		452,900,000
Other ownership interests, mortgage debt						55,300,000
Other ownership interests, contributed capital, working capital contribution					$ 2,900,000	5,000,000
Consolidated property partnerships, tranche one [Member] | Third party [Member]
Noncontrolling Interest [Line Items]
Other ownership interests, contributed capital						191,400,000
Other ownership interests, contributed capital, working capital contribution						$ 2,100,000
Additional tax possibly incurred due to transaction			$ 10,900,000
Consolidated property partnerships, tranche one [Member] | 100 First LLC [Member]
Noncontrolling Interest [Line Items]
Area of Real Estate Property | ft²						467,095
Consolidated property partnerships, tranche two [Member] | Third party [Member]
Noncontrolling Interest [Line Items]
Other ownership interests, contributed capital					$ 261,500,000
Additional tax possibly incurred due to transaction			$ 18,000,000
Consolidated property partnerships, tranche two [Member] | 303 Second Street [Member]
Noncontrolling Interest [Line Items]
Area of Real Estate Property | ft²						740,047
Noncontrolling Interest In Consolidated Subsidiaries [Member]
Noncontrolling Interest [Line Items]
Contribution by noncontrolling interest in consolidated property partnership	$ 124,452,000	$ 474,000
Noncontrolling Interest In Consolidated Subsidiaries [Member] | Kilroy Realty, L.P. [Member]
Noncontrolling Interest [Line Items]
Contribution by noncontrolling interest in consolidated property partnership	(3,615,000)
Common Stock Additional Paid-in Capital [Member]
Noncontrolling Interest [Line Items]
Contribution by noncontrolling interest in consolidated property partnership	$ 328,997,000

Noncontrolling Interests on t91

Noncontrolling Interests on the Operating Partnership's Consolidated Financial Statements (Details) $ in Millions	Dec. 31, 2017	Nov. 30, 2017USD ($)	Dec. 31, 2016	Aug. 30, 2016USD ($)property
Noncontrolling Interest [Line Items]
Company owned general partnership interest	97.90%		97.50%
Consolidated property partnerships [Member]
Noncontrolling Interest [Line Items]
Real estate investments, joint ventures				$ 1,200
Consolidated property partnerships [Member] | Third party [Member]
Noncontrolling Interest [Line Items]
Number of buildings | property				2
Real estate investments, joint ventures				$ 1,200
Other ownership interests, contributed capital		$ 54.4		$ 452.9
Company owned general partnership interest				44.00%
Other ownership interests, mortgage debt				$ 55.3

Stockholders' Equity of the C92

Stockholders' Equity of the Company (Details Textuals) - USD ($)	Aug. 15, 2017	Mar. 30, 2017	Dec. 30, 2016	Dec. 13, 2016	Jan. 31, 2017	Mar. 31, 2016	Jul. 31, 2015	Mar. 31, 2012	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Feb. 23, 2016	Dec. 31, 2014
Class of Stock [Line Items]
Original issuance costs of redeemed preferred units (Note 14)											$ 7,589,000	$ 0	$ 0
At market stock aggregate gross sales price of common stock							$ 249,800,000
Common stock, shares issued					4,427,500		3,733,766
Aggregate gross proceeds					$ 308,800,000						$ 326,058,000	$ 31,117,000	$ 387,398,000
Shares issued, price per share					$ 1.90		$ 66.19
Aggregate net proceeds after sales agent compensation							$ 249,600,000
Stock repurchase program, number of shares authorized to be repurchased														4,000,000
Stock repurchase program, remaining number of shares authorized to be repurchased											4,935,826			4,988,025
Stock repurchased during period, shares						52,199
Treasury stock acquired, average cost per share						$ 55.45
Stock repurchased during period, value						$ 2,900,000
Dividends declared per common share			$ 1.90	$ 1.90					$ 0.375	$ 0.375	$ 1.65	$ 3.375	$ 1.40
Common stock [Member]
Class of Stock [Line Items]
Common stock, shares issued										93,219,439	98,620,333	93,219,439
Dividends declared per common share										$ 2.275	$ 1.650	$ 3.375	$ 1.400
Series G Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock (in shares)		4,000,000								4,000,000		4,000,000
Preferred stock liquidation preference										$ 100,000,000	$ 0	$ 100,000,000
Preferred stock dividend rate (percentage)		6.875%						6.875%			0.00%	6.875%
Preferred units, issued										4,000,000	0	4,000,000
Series H Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock (in shares)	4,000,000									4,000,000		4,000,000
Preferred Stock, Liquidation Preference Per Share	$ 25
Preferred stock liquidation preference	$ 100,000,000									$ 100,000,000	$ 0	$ 100,000,000
Preferred stock dividend rate (percentage)	6.375%										0.00%	6.375%
Preferred units, issued										4,000,000	0	4,000,000
Issuance of Equity under ATM Program [Member]
Class of Stock [Line Items]
At market stock aggregate gross sales price of common stock															$ 300,000,000
Aggregate gross proceeds											$ 17,700,000	$ 32,300,000	$ 140,100,000
Aggregate net proceeds after sales agent compensation											17,500,000	$ 31,900,000	$ 138,200,000
Issuance of Equity under ATM Program [Member] | Common stock [Member]
Class of Stock [Line Items]
At market stock aggregate gross sales price of common stock											$ 200,100,000
Common stock, shares issued											2,694,242
At market stock offering program remained available for issuance											$ 99,900,000
Series G Cumulative Redeemable Preferred Unit [Member]
Class of Stock [Line Items]
Preferred stock (in shares)		4,000,000
Preferred Stock, Liquidation Preference Per Share		$ 25
Preferred stock liquidation preference		$ 100,000,000

Stockholders' Equity of the C93

Stockholders' Equity of the Company (Details) - USD ($) $ / shares in Units, $ in Thousands	Jan. 13, 2017	Dec. 30, 2016	Dec. 13, 2016	Jan. 31, 2017	Jul. 31, 2015	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Aug. 15, 2017	Mar. 30, 2017
Dividends Payable [Line Items]
Aggregate gross proceeds				$ 308,800				$ 326,058	$ 31,117	$ 387,398
Aggregate net proceeds after selling commissions					$ 249,600
Accrued dividend and distributions
Accrued dividends and distributions							$ 222,306	$ 43,448	$ 222,306
Dividends declared per common share		$ 1.90	$ 1.90			$ 0.375	$ 0.375	$ 1.65	$ 3.375	$ 1.40
Payments of special cash dividends	$ 184,300
Payments of dividends, common stock	$ 36,400							$ 340,697	$ 137,444	$ 126,839
Summary of shares and units
Common stock							93,219,439	98,620,333	93,219,439
Common stockholders and noncontrolling unitholders [Member]
Accrued dividend and distributions
Accrued dividends and distributions							$ 220,650	$ 43,448	$ 220,650
Common stock [Member]
Accrued dividend and distributions
Accrued dividends and distributions							$ 212,074	$ 41,914	$ 212,074
Dividends declared per common share							$ 2.275	$ 1.650	$ 3.375	$ 1.400
Summary of shares and units
Common stock							93,219,439	98,620,333	93,219,439
Capital units [Member]
Accrued dividend and distributions
Accrued dividends and distributions							$ 5,418	$ 883	$ 5,418
Preferred Stock [Member]
Accrued dividend and distributions
Accrued dividends and distributions							$ 1,656	$ 0	$ 1,656
Series G Preferred Stock [Member]
Summary of shares and units
Preferred units, issued							4,000,000	0	4,000,000
Preferred stock (in shares)							4,000,000		4,000,000			4,000,000
Series H Preferred Stock [Member]
Summary of shares and units
Preferred units, issued							4,000,000	0	4,000,000
Preferred stock (in shares)							4,000,000		4,000,000		4,000,000
Restricted Stock Units (RSUs) [Member]
Accrued dividend and distributions
Accrued dividends and distributions							$ 3,158	$ 651	$ 3,158
Time-Based Restricted Stock Units (RSUs) [Member]
Summary of shares and units
RSUs							1,395,189	1,488,724	1,395,189
Issuance of Equity under ATM Program [Member]
Dividends Payable [Line Items]
Shares of common stock sold during the period								235,077	451,398	1,866,267
Aggregate gross proceeds								$ 17,700	$ 32,300	$ 140,100
Aggregate net proceeds after selling commissions								17,500	31,900	138,200
Kilroy Realty, L.P. [Member]
Dividends Payable [Line Items]
Aggregate gross proceeds								326,058	31,117	387,398
Accrued dividend and distributions
Accrued dividends and distributions							$ 222,306	43,448	222,306
Payments of dividends, common stock								$ 340,697	$ 137,444	$ 126,839
Kilroy Realty, L.P. [Member] | Capital units [Member]
Summary of shares and units
Noncontrolling common units							2,381,543	2,077,193	2,381,543
Kilroy Realty, L.P. [Member] | Restricted Stock Units (RSUs) [Member]
Accrued dividend and distributions
Accrued dividends and distributions							$ 3,158		$ 3,158
Kilroy Realty, L.P. [Member] | Market measure-based Restricted Stock Units (RSUs) [Member]
Summary of shares and units
Number of RSUs outstanding							659,051	665,110	659,051

Preferred and Common Units of94

Preferred and Common Units of the Operating Partnership (Details Textuals) - USD ($) $ / shares in Units, $ in Thousands	Aug. 15, 2017	Mar. 30, 2017	Jan. 13, 2017	Jan. 31, 2017	Jul. 31, 2015	Mar. 31, 2012	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Mar. 31, 2016
Class of Stock [Line Items]
Original issuance costs of redeemed preferred units (Note 14)							$ 7,589	$ 0	$ 0
Common stock, shares issued				4,427,500	3,733,766
Payments of special cash dividends			$ 184,300
Aggregate gross proceeds				$ 308,800			326,058	31,117	387,398
Shares issued, price per share				$ 1.90	$ 66.19
At market stock aggregate gross sales price of common stock					$ 249,800
Aggregate net proceeds after sales agent compensation					$ 249,600
Distributions paid to common unitholders			$ (36,400)				$ (340,697)	$ (137,444)	$ (126,839)
Brannan St Project [Member]
Class of Stock [Line Items]
Business acquisition, equity interest issued or issuable, number of shares								867,701
Share price										$ 55.36
Common stock, par value							$ 0.01			$ 0.01
Series H Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock (in shares)	4,000,000							4,000,000
Preferred stock, dividend rate	6.375%						0.00%	6.375%
Series G Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock (in shares)		4,000,000						4,000,000
Preferred stock, dividend rate		6.875%				6.875%	0.00%	6.875%

Preferred and Common Units of95

Preferred and Common Units of the Operating Partnership (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 30, 2016	Dec. 13, 2016	Jan. 31, 2017	Jul. 31, 2015	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Aggregate gross proceeds			$ 308,800				$ 326,058	$ 31,117	$ 387,398
Aggregate net proceeds after selling commissions				$ 249,600
Summary of units
Company owned general partnership interest						97.50%	97.90%	97.50%
Ownership interest of noncontrolling interest						2.50%	2.10%	2.50%
Dividends declared per common share	$ 1.90	$ 1.90			$ 0.375	$ 0.375	$ 1.65	$ 3.375	$ 1.40
Accrued distributions
Accrued dividends and distributions						$ 222,306	$ 43,448	$ 222,306
Restricted Stock Units (RSUs) [Member]
Accrued distributions
Accrued dividends and distributions						$ 3,158	$ 651	$ 3,158
Common stock [Member]
Summary of units
Dividends declared per common share						$ 2.275	$ 1.650	$ 3.375	$ 1.400
Accrued distributions
Accrued dividends and distributions						$ 212,074	$ 41,914	$ 212,074
Capital units [Member]
Accrued distributions
Accrued dividends and distributions						5,418	883	5,418
Kilroy Realty, L.P. [Member]
Class of Stock [Line Items]
Aggregate gross proceeds							326,058	31,117	$ 387,398
Accrued distributions
Accrued dividends and distributions						$ 222,306	$ 43,448	$ 222,306
Kilroy Realty, L.P. [Member] | Restricted Stock Units (RSUs) [Member]
Summary of units
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number						1,395,189	1,488,724	1,395,189
Accrued distributions
Accrued dividends and distributions						$ 3,158		$ 3,158
Kilroy Realty, L.P. [Member] | Market measure-based Restricted Stock Units (RSUs) [Member]
Summary of units
Number of RSUs outstanding						659,051	665,110	659,051
Kilroy Realty, L.P. [Member] | Partners Capital Common Unit [Member]
Accrued distributions
Accrued dividends and distributions						$ 220,650	$ 43,448	$ 220,650
Kilroy Realty, L.P. [Member] | Partners capital general partner [Member]
Accrued distributions
Accrued dividends and distributions						212,074	41,914	212,074
Kilroy Realty, L.P. [Member] | Partners capital limited partner [Member]
Accrued distributions
Accrued dividends and distributions						5,418	883	5,418
Kilroy Realty, L.P. [Member] | Partners Capital Preferred Units [Member]
Accrued distributions
Accrued dividends and distributions						$ 1,656	$ 0	$ 1,656
Kilroy Realty, L.P. [Member] | Series G Cumulative Redeemable Preferred Unit [Member]
Summary of units
Preferred units outstanding						4,000,000	0	4,000,000
Kilroy Realty, L.P. [Member] | Series H Cumulative Redeemable Preferred Unit [Member]
Summary of units
Preferred units outstanding						4,000,000	0	4,000,000
Kilroy Realty, L.P. [Member] | Capital units [Member]
Summary of units
Company owned common units in the Operating Partnership						93,219,439	98,620,333	93,219,439
Noncontrolling common units of the Operating Partnership						2,381,543	2,077,193	2,381,543
Issuance of Equity under ATM Program [Member]
Class of Stock [Line Items]
Shares of common stock sold during the period							235,077	451,398	1,866,267
Common units exchanged for shares of common stock by the Company							235,077	451,398	1,866,267
Aggregate gross proceeds							$ 17,700	$ 32,300	$ 140,100
Aggregate net proceeds after selling commissions							$ 17,500	$ 31,900	$ 138,200

Share-Based Compensation - Stoc

Share-Based Compensation - Stockholder Approved Share-Based Incentive Compensation Plan (Details)	Dec. 31, 2017shares
Shareholder Meeting Date May 21, 2015 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, number of shares requested	9,220,000
Kilroy Realty 2006 Incentive Award Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, number of shares available for grant	1,946,554

Share-Based Compensation - Exec

Share-Based Compensation - Executive Officer and Key Employee Share-Based Compensation Programs (Details) - Executive officer share-based compensation programs [Member]	12 Months Ended
	Dec. 31, 2017
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, award requisite service period	1 year
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, award requisite service period	5 years

Share-Based Compensation - 2017

Share-Based Compensation - 2017, 2016 and 2015 Share-Based Compensation Grants (Details) - shares	Feb. 24, 2017	Jan. 28, 2016	Jan. 27, 2015	Feb. 28, 2017	Dec. 31, 2017	Dec. 31, 2016
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period				229,976
Restricted Stock Units (RSUs) [Member] | Chief Executive Officer [Member] | Executive officer share-based compensation programs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period		294,821	212,468
Market measure-based Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period	130,956	168,077	127,657
Time-Based Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period		126,744	84,811	99,020
Time-Based Restricted Stock Units (RSUs) [Member] | Executive officer share-based compensation programs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period					43,081	47,003

Share-Based Compensation - 2099

Share-Based Compensation - 2017, 2016 and 2015 Performance-Based RSU Grants (Details) - USD ($) $ / shares in Units, $ in Millions	Feb. 24, 2017	Jan. 28, 2016	Jan. 27, 2015	Feb. 28, 2012	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Expected share price volatility				33.00%
Risk-free interest rate				1.35%
Remaining expected life				6 years 6 months
2017 Performance-Based RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting period					3 years
Performance-based RSUs achievement target, percent					131.00%
Fair value RSUs granted	$ 10.3
2016 Performance-Based RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting period						3 years
Performance-based RSUs achievement target, percent						144.00%
2015 Performance-Based RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting period							3 years
Performance-based RSUs achievement target, percent							150.00%
Market measure-based Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period	130,956	168,077	127,657
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Fair value per share on valuation date					$ 78.97
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Exercise Price			$ 75.34
Expected share price volatility	21.00%	26.00%	20.00%
Risk-free interest rate	1.39%	1.13%	0.92%
Remaining expected life	2 years 10 months	2 years 11 months	2 years 11 months
Market measure-based RSU estimate of probable [Member] | Market measure-based Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Estimated RSUs earned based on FFO	170,994	241,438	185,510
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Fair value per share on valuation date	$ 80.89	$ 57.08	$ 78.55
Chief Executive Officer [Member] | Executive officer share-based compensation programs [Member] | Market measure-based Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value RSUs granted		$ 9.6	$ 10.1

Share-Based Compensation - 2100

Share-Based Compensation - 2017, 2016 and 2015 Time-Based RSU Grants (Details) - Time-Based Restricted Stock Units (RSUs) [Member] - USD ($) $ / shares in Units, $ in Millions	Feb. 24, 2017	Feb. 03, 2017	Jan. 28, 2016	Jan. 27, 2015	Feb. 28, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value RSUs granted			$ 7.1	$ 6.4	$ 7.5
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Exercise Price	$ 77.16	$ 73.30	$ 56.23
RSUs granted (in units)	57,901	41,119

Share-Based Compensation - Summ

Share-Based Compensation - Summary of Market-Measure Based RSUs 1 (Details) - Market measure-based Restricted Stock Units (RSUs) [Member] - $ / shares	Feb. 24, 2017	Jan. 28, 2016	Jan. 27, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSU weighted average fair value, beginning balance (per share)				$ 64.95
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period	130,956	168,077	127,657
Fair value per share on valuation date				$ 78.97
Share-based compensation arrangement by share-based payment Award, equity instruments other than options, vested in period				194,991	36,914	0
Share-based compensation arrangement by share-based payment Award, equity instruments other than options, vested in period, weighted average grant date fair value				$ 64.93
Share based compensation arrangements, dividends, weighted average grant date fair value				73
Share-based compensation arrangement by share-based payment Award, equity instruments other than options, forfeited in period, weighted average grant date fair value				78.55
RSU weighted average fair value, ending balance (per share)				$ 68.83	$ 64.95
Kilroy Realty, L.P. [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of RSUs outstanding, beginning balance				659,051
Number of RSUs outstanding, ending balance				665,110	659,051
Nonvested Restricted Stock Units RSU [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period				170,994	258,393	191,483
Fair value per share on valuation date				$ 78.97	$ 57.36	$ 79.25
Share-based compensation arrangement by share-based payment Award, equity instruments other than options, vested in period				188,048
Share based compensation arrangement by share based payment award equity instruments other than options issuance of dividend equivalents in period				23,539
Share-based compensation arrangement by share-based payment award, equity instruments other than options, forfeited in period				(426)
Number of RSUs outstanding, ending balance				665,110
Vested Restricted Stock Units RSU [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vested RSUs, beginning balance				0
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period				0
Share-based compensation arrangement by share-based payment Award, equity instruments other than options, vested in period				188,048
Share-based compensation arrangement by share-based payment award, equity instruments other than options, settled in period				(136,191)
Share based compensation arrangement by share based payment award equity instruments other than options issuance of dividend equivalents in period				6,943
Share-based compensation arrangement by share-based payment award, equity instruments other than options, forfeited in period				(3,128)
Vested RSUs, ending balance				55,672	0
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total RSUs, beginning balance				659,051
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period				170,994
Share-based compensation arrangement by share-based payment Award, equity instruments other than options, vested in period				0
Share-based compensation arrangement by share-based payment award, equity instruments other than options, settled in period				(136,191)
Share based compensation arrangement by share based payment award equity instruments other than options issuance of dividend equivalents in period				30,482
Share-based compensation arrangement by share-based payment award, equity instruments other than options, forfeited in period				(3,554)
Total RSUs, ending balance				720,782	659,051
Kilroy Realty 2006 Incentive Award Plan [Member] | Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, equity instruments other than options, settled in period				(72,938)

Share-Based Compensation - S102

Share-Based Compensation - Summary of Market-Measure Based RSUs 2 (Details) - Market measure-based Restricted Stock Units (RSUs) [Member] - USD ($) $ / shares in Units, $ in Thousands	Feb. 24, 2017	Jan. 28, 2016	Jan. 27, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period	130,956	168,077	127,657
Fair value per share on valuation date				$ 78.97
Share-based compensation arrangement by share-based payment Award, equity instruments other than options, vested in period				194,991	36,914	0
Nonvested Restricted Stock Units RSU [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period				170,994	258,393	191,483
Fair value per share on valuation date				$ 78.97	$ 57.36	$ 79.25
Share-based compensation arrangement by share-based payment Award, equity instruments other than options, vested in period				188,048
Vested Restricted Stock Units RSU [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period				0
Share-based compensation arrangement by share-based payment Award, equity instruments other than options, vested in period				188,048
Share-based compensation arrangement by share-based payment award, equity instruments other than options, vested in period, fair value				$ 14,270	$ 2,788	$ 0

Share-Based Compensation - S103

Share-Based Compensation - Summary of Time-Based RSUs 1 (Details) - Time-Based Restricted Stock Units (RSUs) [Member] - USD ($)	Jan. 28, 2016	Jan. 27, 2015	Feb. 28, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vested RSUs, beginning balance				1,395,189
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period	126,744	84,811	99,020
Share-based compensation arrangement by share-based payment Award, equity instruments other than options, vested in period				228,095	130,784	107,541
Vested RSUs, ending balance				1,488,724	1,395,189
Nonvested Restricted Stock Units RSU [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of RSUs outstanding, beginning balance				366,439
RSU weighted average fair value, beginning balance (per share)				$ 59.07
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period				142,101	173,747	98,802
Fair value per share on valuation date				$ 74.91	$ 58.29	$ 74.49
Share-based compensation arrangement by share-based payment Award, equity instruments other than options, vested in period				172,731
Share-based compensation arrangement by share-based payment Award, equity instruments other than options, vested in period, weighted average grant date fair value				$ 57.77
Share based compensation arrangement by share based payment award equity instruments other than options issuance of dividend equivalents in period				8,601
Share based compensation arrangement by share based payment award, non-option equity instruments, transfers				(10,610)
Share-based compensation arrangement by share-based payment award, equity instruments other than options, weighted average transfers				$ 60.16
Share based compensation arrangements, dividends, weighted average grant date fair value				$ 73
Share based compensation arrangement by share based payment award, forfeitures				(2,254)
Share based compensation, weighted average fair value of forfeitures				$ 63.27
Number of RSUs outstanding, ending balance				331,546	366,439
RSU weighted average fair value, ending balance (per share)				$ 66.83	$ 59.07
Vested Restricted Stock Units RSU [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vested RSUs, beginning balance				1,028,750
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period				0
Share-based compensation arrangement by share-based payment Award, equity instruments other than options, vested in period				172,731
Settlement of restricted stock units for shares of common stock, shares				(171,093)
Share based compensation arrangement by share based payment award equity instruments other than options issuance of dividend equivalents in period				55,364
Share based compensation arrangement by share based payment award, non-option equity instruments, transfers				0
Share based compensation arrangement by share based payment award, forfeitures				0
Repurchase of common stock and restricted stock units, shares				(4,824)
Vested RSUs, ending balance				1,080,928	1,028,750
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total RSUs, beginning balance				1,395,189
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period				142,101
Share-based compensation arrangement by share-based payment Award, equity instruments other than options, vested in period				0
Settlement of restricted stock units for shares of common stock, shares				(171,093)
Share based compensation arrangement by share based payment award equity instruments other than options issuance of dividend equivalents in period				63,965
Share based compensation arrangement by share based payment award, non-option equity instruments, transfers				(10,610)
Share based compensation arrangement by share based payment award, forfeitures				(2,254)
Repurchase of common stock and restricted stock units, shares				(4,824)
Total RSUs, ending balance				1,412,474	1,395,189
Kilroy Realty 2006 Incentive Award Plan [Member] | Vested Restricted Stock Units RSU [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Settlement of restricted stock units for shares of common stock, shares				(77,866)

Share-Based Compensation - S104

Share-Based Compensation - Summary of Time-Based RSUs 2 (Details) - Time-Based Restricted Stock Units (RSUs) [Member] - USD ($) $ / shares in Units, $ in Thousands	Jan. 28, 2016	Jan. 27, 2015	Feb. 28, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period	126,744	84,811	99,020
Share-based compensation arrangement by share-based payment Award, equity instruments other than options, vested in period				(228,095)	(130,784)	(107,541)
Nonvested Restricted Stock Units RSU [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period				142,101	173,747	98,802
Fair value per share on valuation date				$ 74.91	$ 58.29	$ 74.49
Share-based compensation arrangement by share-based payment Award, equity instruments other than options, vested in period				(172,731)
Vested Restricted Stock Units RSU [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period				0
Share-based compensation arrangement by share-based payment Award, equity instruments other than options, vested in period				(172,731)
Share-based compensation arrangement by share-based payment award, equity instruments other than options, vested in period, fair value				$ 16,735	$ 8,438	$ 7,528

Share-Based Compensation - S105

Share-Based Compensation - Summary of Nonvested Restricted Stock 1 (Details) - Restricted Stock [Member] - $ / shares	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period		0	0	0
RSU weighted average fair value, beginning balance (per share)	$ 47.93	$ 47.93
Share-based compensation arrangement by share-based payment award, equity instruments other than options, weighted average transfers		60.16
Share-based compensation arrangement by share-based payment Award, equity instruments other than options, vested in period, weighted average grant date fair value		46.39
RSU weighted average fair value, ending balance (per share)		$ 55.23	$ 47.93
Nonvested Restricted Stock Units RSU [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of RSUs outstanding, beginning balance	36,535	36,535
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period		10,610
Number of RSUs outstanding, ending balance		22,884	36,535
Vested Restricted Stock Units RSU [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment Award, equity instruments other than options, vested in period		(24,261)	(24,262)	(24,264)
Repurchase of common stock and restricted stock units, shares	(10,792)

Share-Based Compensation - S106

Share-Based Compensation - Summary of Nonvested Restricted Stock 2 (Details) - Restricted Stock [Member] - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, equity instruments other than options, grants in period		0	0	0
Fair value per share on valuation date		$ 0	$ 0	$ 0
Share-based compensation arrangement by share-based payment award, equity instruments other than options, vested in period, fair value	$ 1,781		$ 1,527	$ 1,725
Vested Restricted Stock Units RSU [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment Award, equity instruments other than options, vested in period		24,261	24,262	24,264

Share-Based Compensation - S107

Share-Based Compensation - Summary of Stock Options (Textual) (Details) - USD ($) $ / shares in Units, $ in Millions	Feb. 22, 2012	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options vested (in shares)		261,000	267,000	298,000
Stock options vested		$ 2.4	$ 2.5	$ 2.7
Kilroy Realty 2006 Incentive Award Plan [Member] | Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, options, withheld in period		15,270	25,680	62,072
Share-based compensation arrangement by share-based payment award, options, withheld in period, intrinsic value		$ 1.2	$ 1.8	$ 3.9
Management [Member] | Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, options, grants in period, gross	1,550,000
Share price	$ 42.61
Share-based compensation arrangement by share-based payment award, award vesting period	5 years
Share-based compensation arrangement by share-based payment award, expiration period	10 years

Share-Based Compensation - S108

Share-Based Compensation - Summary of Stock Options 1 (Details) - Employee Stock Option [Member]	1 Months Ended
	Feb. 28, 2012$ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 9.20
Expected share price volatility	33.00%
Risk-free interest rate	1.35%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate	3.80%
Remaining expected life	6 years 6 months

Share-Based Compensation - S109

Share-Based Compensation - Summary of Stock Options 2 (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, options, outstanding, weighted average remaining contractual term	4 years 1 month
Share-based compensation arrangement by share-based payment award, options, exercisable, weighted average remaining contractual term	4 years 1 month
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, options, outstanding, number	26,500	314,500
Share-based compensation arrangement by share-based payment award, options, outstanding, weighted average exercise price	$ 42.61
Share-based compensation arrangement by share-based payment award, options, outstanding, intrinsic value	$ 0.8	$ 9.6
Exercise of stock options, shares	285,000
Share-based compensation arrangements by share-based payment award, options, exercises in period, weighted average exercise price	$ 42.61
Share-based compensation arrangement by share-based payment award, options, exercises in period, intrinsic value	$ 8.8
Share-based compensation arrangement by share-based payment award, options, forfeitures in period	(3,000)
Share-based compensation arrangement by share-based payment award, options, forfeitures in period, wighted average exercise price	$ 42.61
Share-based compensation arrangement by share-based payment award, options, forfeitures and expirations in period, intrinsic value	$ 0.1
Share-based compensation arrangement by share-based payment award, options, exercisable, number	26,500
Share-based compensation arrangement by share-based payment award, options, exercisable, intrinsic value	$ 0.8

Share-Based Compensation - Shar

Share-Based Compensation - Share-Based Compensation Cost Recorded During the Period (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Allocated share-based compensation expense		$ 26.3	$ 26.6	$ 18.9
Share-based compensation costs		7.3	$ 5.6	$ 3.3
Unrecognized compensation costs		$ 27.2
Cost not yet recognized, period for recognition	1 year 11 months

Employee Benefit Plans Employee

Employee Benefit Plans Employee Benefit Plans (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2007
Retirement Benefits [Abstract]
Eligibility period for 401K savings plan, number of months	3 months
Defined Contribution Plan - maximum participant deferral percent	60.00%
Defined Contribution Plan - employer match per dollar of participant contribution	$ 0.50
Defined Contribution Plan - maximum employer match percentage	10.00%
Defined Contribution Plan - contributions made	$ 1,300,000	$ 1,200,000	$ 1,100,000
Deferred Compensation - maximum participant deferral percent				70.00%
Deferred Compensation - maximum director fees and bonuses that may be deferred (percent)				100.00%
Deferred Compensation - mandatory Company contributions as percentage of gross monthly salary (percent)				10.00%
Deferred Compensation - liability under Plan	$ 20,600,000	$ 14,700,000

Future Minimum Rent (Details)

Future Minimum Rent (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Future contractual minimum rent under operating lease
2,018		$ 555,393
2,019		546,587
2,020		525,637
2,021		497,566
2,022		476,146
Thereafter		2,569,163
Total	$ 251,400	$ 5,170,492

Commitments and Contingencie113

Commitments and Contingencies (Details) $ in Thousands	Dec. 31, 2016USD ($)
Summary of minimum commitment
2,018	$ 4,957
2,019	4,957
2,020	4,957
2,021	4,957
2,022	4,957
Thereafter	226,633
Total	$ 251,418

Commitments and Contingencie114

Commitments and Contingencies (Details 1) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)Extensions	Dec. 31, 2016USD ($)
Long-term Purchase Commitment [Line Items]
Commitments for contracts and executed leases, operating and redevelopment and development properties	$ 696.1
Period after which ground lease rentals are adjusted based on fair market value and the Consumer Price Index	5 years
Annual ground lease rental obligations limit	$ 1
Duration of ground lease prior to increase five years	5 years
Average annual percentage rent for previous five years (percent)	50.00%
Duration of ground lease prior to increase ten years	10 years
Average annual percentage rent for previous ten years (percent)	60.00%
Accrued environmental remediation liabilities	$ 28.3	$ 25.1
Ten year ground lease extension option [Member]
Long-term Purchase Commitment [Line Items]
Number of extension options | Extensions	3
Ground lease extension option term	10 years
Forty-five year ground lease extension option [Member]
Long-term Purchase Commitment [Line Items]
Number of extension options | Extensions	1
Ground lease extension option term	45 years
Property damage litigation case [Member]
Long-term Purchase Commitment [Line Items]
Proceeds from legal settlements		$ 5

Fair Value Measurements and 115

Fair Value Measurements and Disclosures (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair value adjustment of marketable securities and deferred compensation plan liability
Net gain on marketable securities	$ 3,023	$ 1,130	$ (269)
Fair Value (Level 1) [Member]
Assets and Liabilities Reported at Fair Value
Marketable securities	$ 20,674	$ 14,773

Fair Value Measurements and 116

Fair Value Measurements and Disclosures (Details 1) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Carrying value [Member] | Secured debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt instrument, fair value disclosure	$ 340,800	$ 472,772
Carrying value [Member] | Unsecured debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt instrument, fair value disclosure	2,006,263	1,847,351
Fair value [Member] | Secured debt [Member] | Fair value (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt instrument, fair value disclosure	346,858	469,234
Fair value [Member] | Unsecured debt [Member] | Fair value (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt instrument, fair value disclosure	$ 2,077,199	$ 1,900,487

Net Income Available to Comm117

Net Income Available to Common Stockholders Per Share of the Company (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Numerator:
Net income attributable to Kilroy Realty, L.P.									$ 164,612	$ 293,788	$ 234,081
Total preferred dividends and distributions	$ 0	$ (4,552)	$ (1,615)	$ (7,196)	$ (3,312)	$ (3,313)	$ (3,312)	$ (3,313)	(13,363)	(13,250)	(13,250)
Allocation to participating securities (1)									(1,975)	(3,839)	(1,634)
Numerator for basic and diluted net income available to common stockholders									$ 149,274	$ 276,699	$ 219,197
Denominator:
Basic weighted average vested shares outstanding									98,113,561	92,342,483	89,854,096
Effect of dilutive securities – contingently issuable shares and stock options									613,770	680,551	541,679
Diluted weighted average vested shares and common stock equivalents outstanding									98,727,331	93,023,034	90,395,775
Basic earnings per share:
Net income available to common stockholders per share - basic	$ 0.28	$ 0.67	$ 0.30	$ 0.27	$ 0.29	$ 0.54	$ 0.32	$ 1.85	$ 1.52	$ 3	$ 2.44
Diluted earnings per share:
Net income available to common stockholders per share - diluted	$ 0.28	$ 0.67	$ 0.30	$ 0.26	$ 0.29	$ 0.54	$ 0.31	$ 1.84	$ 1.51	$ 2.97	$ 2.42

Net Income Available to Comm118

Net Income Available to Common Unitholders Per Unit of the Operating Partnership (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Numerator:
Net income attributable to Kilroy Realty, L.P.									$ 164,612	$ 293,788	$ 234,081
Total preferred dividends and distributions	$ 0	$ (4,552)	$ (1,615)	$ (7,196)	$ (3,312)	$ (3,313)	$ (3,312)	$ (3,313)	(13,363)	(13,250)	(13,250)
Allocation to participating securities (1)									(1,975)	(3,839)	(1,634)
Numerator for basic and diluted net income available to common stockholders									$ 149,274	$ 276,699	$ 219,197
Denominator:
Basic weighted average vested shares outstanding									98,113,561	92,342,483	89,854,096
Effect of dilutive securities – contingently issuable shares and stock options									613,770	680,551	541,679
Diluted weighted average vested shares and common stock equivalents outstanding									98,727,331	93,023,034	90,395,775
Basic earnings per unit:
Net income available to common unitholders per unit (dollars per unit)	$ 0.28	$ 0.67	$ 0.30	$ 0.27	$ 0.29	$ 0.54	$ 0.32	$ 1.85	$ 1.52	$ 3	$ 2.44
Diluted earnings per unit:
Net income available to common unitholders per unit (dollars per unit)	$ 0.28	$ 0.67	$ 0.30	$ 0.26	$ 0.29	$ 0.54	$ 0.31	$ 1.84	$ 1.51	$ 2.97	$ 2.42
Kilroy Realty, L.P. [Member]
Numerator:
Net income attributable to Kilroy Realty, L.P.									$ 167,440	$ 300,063	$ 238,137
Total preferred dividends and distributions	$ 0	$ (4,552)	$ (1,615)	$ (7,196)	$ (3,312)	$ (3,313)	$ (3,312)	$ (3,313)	(13,363)	(13,250)	(13,250)
Allocation to participating securities (1)									(1,975)	(3,839)	(1,634)
Numerator for basic and diluted net income available to common stockholders									$ 152,102	$ 282,974	$ 223,253
Denominator:
Basic weighted average vested shares outstanding									100,246,567	94,771,688	91,645,578
Effect of dilutive securities – contingently issuable shares and stock options									613,770	680,551	541,679
Diluted weighted average vested shares and common stock equivalents outstanding									100,860,337	95,452,239	92,187,257
Basic earnings per unit:
Net income available to common unitholders per unit (dollars per unit)	$ 0.28	$ 0.67	$ 0.30	$ 0.26	$ 0.29	$ 0.54	$ 0.31	$ 1.85	$ 1.52	$ 2.99	$ 2.44
Diluted earnings per unit:
Net income available to common unitholders per unit (dollars per unit)	$ 0.28	$ 0.67	$ 0.30	$ 0.26	$ 0.29	$ 0.54	$ 0.31	$ 1.84	$ 1.51	$ 2.96	$ 2.42

Supplemental Cash Flow Infor119

Supplemental Cash Flow Information of the Company (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
SUPPLEMENTAL CASH FLOWS INFORMATION:
Interest paid, net	$ 67,336	$ 54,295	$ 54,747
Capitalized interest	44,757	47,675	50,923
NON-CASH INVESTING TRANSACTIONS:
Accrual for expenditures for operating properties and development and redevelopment properties	116,089	62,589	109,715
Tenant improvements funded directly by tenants	15,314	18,050	13,387
Assumption of other assets and liabilities in connection with operating and development property acquisitions, net (Note 3)	1,443	5,863	6,254
Accrual for receivable related to development properties	0	1,350	0
Release of holdback funds to third party	0	0	9,279
NON-CASH FINANCING TRANSACTIONS:
Accrual of dividends and distributions payable to common stockholders and common unitholders (Notes 13 and 27)	43,448	220,650	33,336
Accrual of dividends and distributions payable to preferred stockholders and preferred unitholders (Note 13)	0	1,656	1,656
Issuance of common units of the Operating Partnership in connection with an acquisition (Note 3)	0	48,033	0
Secured debt assumed by buyers in connection with land disposition (Note 4)	0	2,322	0
Exchange of common units of the Operating Partnership into shares of the Company’s common stock	$ 10,939	$ 8,893	$ 1,223

Supplemental Cash Flow Infor120

Supplemental Cash Flow Information of the Company - Cash and Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Supplemental Cash Flow Elements [Abstract]
Cash and cash equivalents	$ 57,649	$ 193,418	$ 56,508	$ 23,781
Restricted cash	9,149	56,711	696	75,185
Cash and cash equivalents and restricted cash	$ 66,798	$ 250,129	$ 57,204	$ 98,966

Supplemental Cash Flow Infor121

Supplemental Cash Flow Information of the Operating Partnership (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
SUPPLEMENTAL CASH FLOWS INFORMATION:
Interest paid, net		$ 67,336	$ 54,295	$ 54,747
Capitalized interest		44,757	47,675	50,923
NON-CASH INVESTING TRANSACTIONS:
Accrual for expenditures for operating properties and development and redevelopment properties		116,089	62,589	109,715
Tenant improvements funded directly by tenants		15,314	18,050	13,387
Assumption of other assets and liabilities in connection with operating and development property acquisitions, net (Note 3)		1,443	5,863	6,254
Accrual for receivable related to development properties		0	1,350	0
Release of holdback funds to third party		0	0	9,279
NON-CASH FINANCING TRANSACTIONS:
Accrual of dividends and distributions payable to common stockholders and common unitholders (Notes 14 and 27)		43,448	220,650	33,336
Accrual of dividends and distributions payable to preferred stockholders and preferred unitholders (Note 14)		0	1,656	1,656
Issuance of common units in connection with a development property acquisition (Note 3)		0	48,033	0
Secured debt assumed by buyers in connection with land disposition (Note 4)		0	2,322	0
Kilroy Realty, L.P. [Member]
SUPPLEMENTAL CASH FLOWS INFORMATION:
Interest paid, net		67,336	54,295	54,747
Capitalized interest	$ 47,675		47,675	50,923
NON-CASH INVESTING TRANSACTIONS:
Accrual for expenditures for operating properties and development and redevelopment properties		116,089	62,589	109,715
Tenant improvements funded directly by tenants		15,314	18,050	13,387
Assumption of other assets and liabilities in connection with operating and development property acquisitions, net (Note 3)		1,443	5,863	6,254
Release of holdback funds to third party		0	0	9,279
NON-CASH FINANCING TRANSACTIONS:
Accrual of dividends and distributions payable to common stockholders and common unitholders (Notes 14 and 27)			220,650	33,336
Accrual of dividends and distributions payable to preferred stockholders and preferred unitholders (Note 14)		0	1,656	1,656
Secured debt assumed by buyers in connection with land disposition (Note 4)		$ 0	$ 2,322	$ 0

Supplemental Cash Flow Infor122

Supplemental Cash Flow Information of the Operating Partnership - Cash and Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Other Significant Noncash Transactions [Line Items]
Cash and cash equivalents	$ 57,649	$ 193,418	$ 56,508	$ 23,781
Restricted cash	9,149	56,711	696	75,185
Cash and cash equivalents and restricted cash	66,798	250,129	57,204	98,966
Kilroy Realty, L.P. [Member]
Other Significant Noncash Transactions [Line Items]
Cash and cash equivalents	57,649	193,418	56,508	23,781
Restricted cash	9,149	56,711	696	75,185
Cash and cash equivalents and restricted cash	$ 66,798	$ 250,129	$ 57,204	$ 98,966

Tax Treatment of Distributio123

Tax Treatment of Distributions (Details) - $ / shares	Jan. 13, 2017	Dec. 30, 2016	Dec. 13, 2016	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Dividends declared per common share		$ 1.90	$ 1.90	$ 0.375	$ 0.375		$ 1.65	$ 3.375	$ 1.40
Dividends paid per common share	$ 0.313					$ 1.587
Common stock [Member]
Class of Stock [Line Items]
Dividends declared per common share					$ 2.275		1.650	3.375	1.400
Less: Dividends declared in the current year and paid in the following year							(0.425)	(2.275)	(0.350)
Add: Dividends declared in the prior year and paid in the current year							2.275	0.350	0.350
Dividends paid per common share							$ 3.500	$ 1.450	$ 1.400

Tax Treatment of Distributio124

Tax Treatment of Distributions (Details 1) - $ / shares	Aug. 15, 2017	Mar. 30, 2017	Jan. 13, 2017	Mar. 31, 2012	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Treatment of Dividends Paid [Line Items]
Dividends paid per common share			$ 0.313		$ 1.587
Capital gains, federal statutory tax rate						20.00%
Common stock [Member]
Income Tax Treatment of Dividends Paid [Line Items]
Dividends paid per common share						$ 3.500	$ 1.450	$ 1.400
Series G Preferred Stock [Member]
Income Tax Treatment of Dividends Paid [Line Items]
Preferred stock, dividend rate		6.875%		6.875%		0.00%	6.875%
Series H Preferred Stock [Member]
Income Tax Treatment of Dividends Paid [Line Items]
Preferred stock, dividend rate	6.375%					0.00%	6.375%
Tax treatment, Ordinary income [Member] | Common stock [Member]
Income Tax Treatment of Dividends Paid [Line Items]
Dividends paid per common share						$ 1.356	$ 1.500	$ 0.992
Dividends paid per common share, percentage						70.87%	49.40%	70.86%
Tax treatment, Ordinary income [Member] | Series G Preferred Stock [Member]
Income Tax Treatment of Dividends Paid [Line Items]
Dividends paid per preferred share						$ 0.371	$ 0.848	$ 1.218
Dividend paid per preferred share, percentage						86.43%	49.31%	70.86%
Tax treatment, Ordinary income [Member] | Series H Preferred Stock [Member]
Income Tax Treatment of Dividends Paid [Line Items]
Dividends paid per preferred share						$ 1.033	$ 0.786	$ 1.129
Dividend paid per preferred share, percentage						86.43%	49.31%	70.86%
Tax treatment, Qualified dividend [Member] | Common stock [Member]
Income Tax Treatment of Dividends Paid [Line Items]
Dividends paid per common share						$ 0.002	$ 0.002	$ 0.002
Dividends paid per common share, percentage						0.11%	0.06%	0.13%
Tax treatment, Qualified dividend [Member] | Series G Preferred Stock [Member]
Income Tax Treatment of Dividends Paid [Line Items]
Dividends paid per preferred share						$ 0.001	$ 0.001	$ 0.002
Dividend paid per preferred share, percentage						0.14%	0.06%	0.13%
Tax treatment, Qualified dividend [Member] | Series H Preferred Stock [Member]
Income Tax Treatment of Dividends Paid [Line Items]
Dividends paid per preferred share						$ 0.002	$ 0.001	$ 0.002
Dividend paid per preferred share, percentage						0.14%	0.06%	0.13%
Tax treatment, Return of capital [Member] | Common stock [Member]
Income Tax Treatment of Dividends Paid [Line Items]
Dividends paid per common share						$ 0.344	$ 0	$ 0
Dividends paid per common share, percentage						18.00%	0.00%	0.00%
Tax treatment, Capital gains [Member] | Common stock [Member]
Income Tax Treatment of Dividends Paid [Line Items]
Dividends paid per common share						$ 0	$ 1.212	$ 0.051
Dividends paid per common share, percentage						0.00%	39.89%	3.65%
Tax treatment, Capital gains [Member] | Series G Preferred Stock [Member]
Income Tax Treatment of Dividends Paid [Line Items]
Dividends paid per preferred share						$ 0	$ 0.687	$ 0.063
Dividend paid per preferred share, percentage						0.00%	39.97%	3.65%
Tax treatment, Capital gains [Member] | Series H Preferred Stock [Member]
Income Tax Treatment of Dividends Paid [Line Items]
Dividends paid per preferred share						$ 0	$ 0.637	$ 0.059
Dividend paid per preferred share, percentage						0.00%	39.97%	3.65%
Tax treatment, Unrecaptured section 1250 gains [Member] | Common stock [Member]
Income Tax Treatment of Dividends Paid [Line Items]
Dividends paid per common share						$ 0.211	$ 0.323	$ 0.355
Dividends paid per common share, percentage						11.02%	10.65%	25.36%
Tax treatment, Unrecaptured section 1250 gains [Member] | Series G Preferred Stock [Member]
Income Tax Treatment of Dividends Paid [Line Items]
Dividends paid per preferred share						$ 0.058	$ 0.183	$ 0.436
Dividend paid per preferred share, percentage						13.43%	10.66%	25.36%
Tax treatment, Unrecaptured section 1250 gains [Member] | Series H Preferred Stock [Member]
Income Tax Treatment of Dividends Paid [Line Items]
Dividends paid per preferred share						$ 0.160	$ 0.170	$ 0.404
Dividend paid per preferred share, percentage						13.43%	10.66%	25.36%
Tax treatment [Member] | Common stock [Member]
Income Tax Treatment of Dividends Paid [Line Items]
Dividends paid per common share						$ 1.913	$ 3.037	$ 1.400
Dividends paid per common share, percentage						100.00%	100.00%	100.00%
Tax treatment [Member] | Series G Preferred Stock [Member]
Income Tax Treatment of Dividends Paid [Line Items]
Dividends paid per preferred share						$ 0.430	$ 1.719	$ 1.719
Dividend paid per preferred share, percentage						100.00%	100.00%	100.00%
Tax treatment [Member] | Series H Preferred Stock [Member]
Income Tax Treatment of Dividends Paid [Line Items]
Dividends paid per preferred share						$ 1.195	$ 1.594	$ 1.594
Dividend paid per preferred share, percentage						100.00%	100.00%	100.00%

Quarterly Financial Informat125

Quarterly Financial Information of the Company (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 177,561	$ 181,534	$ 180,598	$ 179,308	$ 168,645	$ 168,348	$ 160,133	$ 145,446	$ 719,001	$ 642,572	$ 581,275
Net income	32,540	75,488	35,306	37,281	35,418	56,375	33,892	178,113	180,615	303,798	238,604
Net income attributable to Kilroy Realty Corporation	28,529	71,110	31,448	33,525	32,738	53,895	32,847	174,308	164,612	293,788	234,081
Total preferred dividends and distributions	0	(4,552)	(1,615)	(7,196)	(3,312)	(3,313)	(3,312)	(3,313)	(13,363)	(13,250)	(13,250)
Net income available to common stockholders	$ 28,529	$ 66,558	$ 29,833	$ 26,329	$ 29,426	$ 50,582	$ 29,535	$ 170,995	$ 151,249	$ 280,538	$ 220,831
Net income (loss) available to common stockholders per share—basic (dollars per share)	$ 0.28	$ 0.67	$ 0.30	$ 0.27	$ 0.29	$ 0.54	$ 0.32	$ 1.85	$ 1.52	$ 3	$ 2.44
Net income (loss) available to common stockholders per share—diluted (dollars per share)	$ 0.28	$ 0.67	$ 0.30	$ 0.26	$ 0.29	$ 0.54	$ 0.31	$ 1.84	$ 1.51	$ 2.97	$ 2.42

Quarterly Financial Informat126

Quarterly Financial Information of the Operating Partnership (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues	$ 177,561	$ 181,534	$ 180,598	$ 179,308	$ 168,645	$ 168,348	$ 160,133	$ 145,446	$ 719,001	$ 642,572	$ 581,275
Net income	32,540	75,488	35,306	37,281	35,418	56,375	33,892	178,113	180,615	303,798	238,604
Net income attributable to the Operating Partnership	28,529	71,110	31,448	33,525	32,738	53,895	32,847	174,308	164,612	293,788	234,081
Total preferred distributions	0	(4,552)	(1,615)	(7,196)	(3,312)	(3,313)	(3,312)	(3,313)	(13,363)	(13,250)	(13,250)
Net income available to common stockholders	$ 28,529	$ 66,558	$ 29,833	$ 26,329	$ 29,426	$ 50,582	$ 29,535	$ 170,995	$ 151,249	$ 280,538	$ 220,831
Net income (loss) available to common stockholders per share—basic (dollars per share)	$ 0.28	$ 0.67	$ 0.30	$ 0.27	$ 0.29	$ 0.54	$ 0.32	$ 1.85	$ 1.52	$ 3	$ 2.44
Net income (loss) available to common stockholders per share—diluted (dollars per share)	$ 0.28	$ 0.67	$ 0.30	$ 0.26	$ 0.29	$ 0.54	$ 0.31	$ 1.84	$ 1.51	$ 2.97	$ 2.42
Kilroy Realty, L.P. [Member]
Revenues	$ 177,561	$ 181,534	$ 180,598	$ 179,308	$ 168,645	$ 168,348	$ 160,133	$ 145,446	$ 719,001	$ 642,572	$ 581,275
Net income	32,540	75,488	35,306	37,281	35,418	56,375	33,892	178,113	180,615	303,798	238,604
Net income attributable to the Operating Partnership	29,013	72,402	31,971	34,054	33,386	55,254	33,590	177,833	167,440	300,063	238,137
Total preferred distributions	0	(4,552)	(1,615)	(7,196)	(3,312)	(3,313)	(3,312)	(3,313)	(13,363)	(13,250)	(13,250)
Net income available to common stockholders	$ 29,013	$ 67,850	$ 30,356	$ 26,858	$ 30,074	$ 51,941	$ 30,278	$ 174,520	$ 154,077	$ 286,813	$ 224,887
Net income (loss) available to common stockholders per share—basic (dollars per share)	$ 0.28	$ 0.67	$ 0.30	$ 0.26	$ 0.29	$ 0.54	$ 0.31	$ 1.85	$ 1.52	$ 2.99	$ 2.44
Net income (loss) available to common stockholders per share—diluted (dollars per share)	$ 0.28	$ 0.67	$ 0.30	$ 0.26	$ 0.29	$ 0.54	$ 0.31	$ 1.84	$ 1.51	$ 2.96	$ 2.42

Subsequent Events (Details)

Subsequent Events (Details) $ in Thousands	Jan. 31, 2018USD ($)ft²	Jan. 29, 2018shares	Jan. 12, 2018USD ($)	Jan. 13, 2017USD ($)	Dec. 31, 2017USD ($)ft²shares	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Subsequent Event [Line Items]
Payments of dividends, common stock				$ 36,400	$ 340,697	$ 137,444	$ 126,839
Outstanding borrowings (1)					$ 2,006,263	1,847,351
Rentable Square Feet | ft²					13,720,597
Subsequent event [Member]
Subsequent Event [Line Items]
Payments of dividends, common stock			$ 43,400
Kilroy Realty, L.P. [Member]
Subsequent Event [Line Items]
Payments of dividends, common stock					$ 340,697	137,444	$ 126,839
Outstanding borrowings (1)					$ 2,006,263	$ 1,847,351
Kilroy Realty, L.P. [Member] | Line of credit [Member] | Subsequent event [Member]
Subsequent Event [Line Items]
Outstanding borrowings (1)	$ 75,000
Kilroy Realty 2006 Incentive Award Plan [Member]
Subsequent Event [Line Items]
Share-based compensation arrangement by share-based payment award, number of shares available for grant | shares					1,946,554
Kilroy Realty 2006 Incentive Award Plan [Member] | Market measure-based Restricted Stock Units (RSUs) [Member] | Chief Executive Officer [Member] | Subsequent event [Member]
Subsequent Event [Line Items]
Share-based compensation arrangement by share-based payment award, number of shares available for grant | shares		56,015
Share-based compensation arrangement by share-based payment award, award requisite service period		3 years
Oyster Point, South San Francisco [Member] | Subsequent event [Member]
Subsequent Event [Line Items]
Rentable Square Feet | ft²	146,000
Purchase price	$ 111,000

Schedule II Valuation and Qu128

Schedule II Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for uncollectible tenant receivables
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 1,712	$ 2,080	$ 1,999
Charged to Costs and Expenses	1,517	0	303
Recoveries (Deductions)	(920)	(368)	(222)
Balance at End of Period (1)	2,309	1,712	2,080
Allowance for deferred rent receivables
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	1,524	1,882	1,989
Charged to Costs and Expenses	1,752	0	242
Recoveries (Deductions)	(38)	(358)	(349)
Balance at End of Period (1)	$ 3,238	$ 1,524	$ 1,882

Schedule III - Real Estate a129

Schedule III - Real Estate and Accumulated Depreciation (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)ft²	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation, amount of encumbrances	$ 339,395
Real Estate and Accumulated Depreciation, Initial Cost of Land	1,726,190
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	2,754,699
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	2,936,888
Real Estate and Accumulated Depreciation, Carrying Amount of Land	1,768,413
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	5,649,364
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	7,417,777
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 1,264,162	$ 1,139,853	$ 994,241	$ 947,664
Rentable Square Feet (unaudited) | ft²	13,720,597
Office Building [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation, amount of encumbrances	$ 339,395
Real Estate and Accumulated Depreciation, Initial Cost of Land	1,033,949
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	2,754,699
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	2,196,321
Real Estate and Accumulated Depreciation, Carrying Amount of Land	1,076,172
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	4,908,797
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	5,984,969
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 1,264,162
Rentable Square Feet (unaudited) | ft²	13,720,597
Office Building [Member] | 23925 Park Sorrento, Calabasas, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation, amount of encumbrances
Real Estate and Accumulated Depreciation, Initial Cost of Land	50
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	2,346
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	505
Real Estate and Accumulated Depreciation, Carrying Amount of Land	50
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	2,851
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	2,901
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 1,785
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	11,873
Office Building [Member] | 23975 Park Sorrento, Calabasas, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 765
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	17,720
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	8,948
Real Estate and Accumulated Depreciation, Carrying Amount of Land	765
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	26,668
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	27,433
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 15,576
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	104,797
Office Building [Member] | 24025 Park Sorrento, Calabasas, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 845
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	15,896
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	8,780
Real Estate and Accumulated Depreciation, Carrying Amount of Land	845
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	24,676
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	25,521
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 14,669
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	108,670
Office Building [Member] | 2829 Townsgate Rd., Thousand Oaks, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 5,248
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	8,001
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	7,991
Real Estate and Accumulated Depreciation, Carrying Amount of Land	5,248
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	15,992
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	21,240
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 11,056
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	84,098
Office Building [Member] | 2240 E. Imperial Highway, El Segundo, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 1,044
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	11,763
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	29,488
Real Estate and Accumulated Depreciation, Carrying Amount of Land	1,048
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	41,247
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	42,295
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 24,400
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	122,870
Office Building [Member] | 2250 E. Imperial Highway, El Segundo, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 2,579
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	29,062
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	35,553
Real Estate and Accumulated Depreciation, Carrying Amount of Land	2,547
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	64,647
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	67,194
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 50,919
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	298,728
Office Building [Member] | 2260 E. Imperial Highway, El Segundo, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 2,518
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	28,370
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	36,620
Real Estate and Accumulated Depreciation, Carrying Amount of Land	2,547
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	64,961
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	67,508
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 11,814
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	298,728
Office Building [Member] | 909 Sepulveda Boulevard, El Segundo, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation, amount of encumbrances
Real Estate and Accumulated Depreciation, Initial Cost of Land	3,577
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	34,042
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	47,184
Real Estate and Accumulated Depreciation, Carrying Amount of Land	3,577
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	81,226
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	84,803
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 35,309
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	244,136
Office Building [Member] | 999 Sepulveda Boulevard, El Segundo, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 1,407
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	34,326
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	13,370
Real Estate and Accumulated Depreciation, Carrying Amount of Land	1,407
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	47,696
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	49,103
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 21,309
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	128,588
Office Building [Member] | 6115 W. Sunset Boulevard, Los Angeles, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 1,313
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	3
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	15,386
Real Estate and Accumulated Depreciation, Carrying Amount of Land	2,455
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	14,247
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	16,702
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 970
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	26,105
Office Building [Member] | 6121 W. Sunset Boulevard, Los Angeles, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 11,120
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	4,256
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	43,912
Real Estate and Accumulated Depreciation, Carrying Amount of Land	8,703
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	50,585
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	59,288
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 4,003
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	91,173
Office Building [Member] | 1525 N. Gower Street, Los Angeles, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 1,318
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	3
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	9,633
Real Estate and Accumulated Depreciation, Carrying Amount of Land	1,318
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	9,636
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	10,954
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 522
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	9,610
Office Building [Member] | 1575 N. Gower Street, Los Angeles, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 22,153
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	51
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	119,891
Real Estate and Accumulated Depreciation, Carrying Amount of Land	22,153
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	119,942
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	142,095
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 4,438
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	251,245
Office Building [Member] | 1500 N. El Centro Avenue, Los Angeles, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 9,235
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	21
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	55,627
Real Estate and Accumulated Depreciation, Carrying Amount of Land	9,235
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	55,648
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	64,883
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 1,907
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	104,504
Office Building [Member] | 1550 N. El Centro Avenue, Los Angeles, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 16,970
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	39
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	135,390
Real Estate and Accumulated Depreciation, Carrying Amount of Land	16,970
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	135,429
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	152,399
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 6,012
Real estate and accumulated depreciation, life used for depreciation	35 years
Office Building [Member] | 6255 Sunset Boulevard, Los Angeles, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation, amount of encumbrances
Real Estate and Accumulated Depreciation, Initial Cost of Land	18,111
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	60,320
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	40,177
Real Estate and Accumulated Depreciation, Carrying Amount of Land	18,111
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	100,497
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	118,608
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 23,147
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	323,920
Office Building [Member] | 3750 Kilroy Airport Way, Long Beach, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	$ 1,941
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	11,022
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	12,963
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	12,963
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 10,005
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	10,457
Office Building [Member] | 3760 Kilroy Airport Way, Long Beach, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	$ 17,467
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	12,031
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	29,498
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	29,498
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 24,461
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	165,278
Office Building [Member] | 3780 Kilroy Airport Way, Long Beach, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	$ 22,319
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	20,119
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	42,438
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	42,438
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 35,747
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	219,745
Office Building [Member] | 3800 Kilroy Airport Way, Long Beach, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	$ 19,408
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	20,176
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	39,584
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	39,584
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 22,575
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	192,476
Office Building [Member] | 3840 Kilroy Airport Way, Long Beach, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	$ 13,586
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	9,635
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	23,221
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	23,221
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 14,695
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	136,026
Office Building [Member] | 3880 Kilroy Airport Way, Long Beach, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	$ 9,704
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	11,167
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	20,871
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	20,871
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 3,118
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	96,035
Office Building [Member] | 3900 Kilroy Airport Way, Long Beach, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	$ 12,615
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	11,397
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	24,012
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	24,012
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 16,058
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	129,893
Office Building [Member] | Kilroy Airport Center, Phase IV, Long Beach, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	$ 4,997
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	4,997
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	4,997
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 4,993
Real estate and accumulated depreciation, life used for depreciation	35 years
Office Building [Member] | 8560 West Sunset Blvd, West Hollywood, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 9,720
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	50,956
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	169
Real Estate and Accumulated Depreciation, Carrying Amount of Land	9,720
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	51,125
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	60,845
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 2,204
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	71,875
Office Building [Member] | 8570 West Sunset Blvd, West Hollywood, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 31,693
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	27,974
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	256
Real Estate and Accumulated Depreciation, Carrying Amount of Land	31,693
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	28,230
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	59,923
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 1,075
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	43,603
Office Building [Member] | 8580 West Sunset Blvd, West Hollywood, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 10,013
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	3,695
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	35
Real Estate and Accumulated Depreciation, Carrying Amount of Land	10,013
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	3,730
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	13,743
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 137
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	7,126
Office Building [Member] | 8590 West Sunset Blvd, West Hollywood, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 39,954
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	27,884
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	272
Real Estate and Accumulated Depreciation, Carrying Amount of Land	39,954
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	28,156
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	68,110
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 1,178
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	56,095
Office Building [Member] | 12100 W. Olympic Boulevard, Los Angeles, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation, amount of encumbrances	$ 170,000
Real Estate and Accumulated Depreciation, Initial Cost of Land	352
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	45,611
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	18,417
Real Estate and Accumulated Depreciation, Carrying Amount of Land	9,633
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	54,747
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	64,380
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 25,353
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	152,048
Office Building [Member] | 12200 W. Olympic Boulevard, Los Angeles, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 4,329
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	35,488
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	23,274
Real Estate and Accumulated Depreciation, Carrying Amount of Land	3,977
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	59,114
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	63,091
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 34,746
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	150,832
Office Building [Member] | 12233 Olympic Blvd, Los Angeles, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation, amount of encumbrances
Real Estate and Accumulated Depreciation, Initial Cost of Land	22,100
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	53,170
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	3,848
Real Estate and Accumulated Depreciation, Carrying Amount of Land	22,100
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	57,018
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	79,118
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 9,610
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	151,029
Office Building [Member] | 12312 W. Olympic Boulevard, Los Angeles, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 3,325
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	12,202
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	11,326
Real Estate and Accumulated Depreciation, Carrying Amount of Land	3,399
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	23,454
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	26,853
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 10,573
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	76,644
Office Building [Member] | 1633 26th Street, Santa Monica, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 2,080
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	6,672
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	3,139
Real Estate and Accumulated Depreciation, Carrying Amount of Land	2,040
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	9,851
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	11,891
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 6,638
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	43,857
Office Building [Member] | 2100 Colorado Avenue, Santa Monica, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation, amount of encumbrances	$ 93,081
Real Estate and Accumulated Depreciation, Initial Cost of Land	5,474
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	26,087
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	14,373
Real Estate and Accumulated Depreciation, Carrying Amount of Land	5,476
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	40,458
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	45,934
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 22,311
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	102,864
Office Building [Member] | 3130 Wilshire Boulevard, Santa Monica, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 8,921
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	6,579
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	14,931
Real Estate and Accumulated Depreciation, Carrying Amount of Land	9,188
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	21,243
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	30,431
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 13,546
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	90,002
Office Building [Member] | 501 Santa Monica Boulevard, Santa Monica, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 4,547
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	12,044
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	13,173
Real Estate and Accumulated Depreciation, Carrying Amount of Land	4,551
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	25,213
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	29,764
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 14,092
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	76,803
Office Building [Member] | 2211 Michelson, Irvine, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 9,319
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	82,836
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	5,779
Real Estate and Accumulated Depreciation, Carrying Amount of Land	9,319
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	88,615
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	97,934
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 24,029
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	271,556
Office Building [Member] | 12225 El Camino Real, Del Mar, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 1,700
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	9,633
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	2,982
Real Estate and Accumulated Depreciation, Carrying Amount of Land	1,673
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	12,642
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	14,315
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 8,274
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	58,401
Office Building [Member] | 12235 El Camino Real, Del Mar, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 1,507
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	8,543
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	8,657
Real Estate and Accumulated Depreciation, Carrying Amount of Land	1,540
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	17,167
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	18,707
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 8,927
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	53,751
Office Building [Member] | 12340 El Camino Real, Del Mar, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 4,201
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	13,896
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	8,851
Real Estate and Accumulated Depreciation, Carrying Amount of Land	4,201
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	22,747
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	26,948
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 10,375
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	88,377
Office Building [Member] | 12390 El Camino Real, Del Mar, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 3,453
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	11,981
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	1,380
Real Estate and Accumulated Depreciation, Carrying Amount of Land	3,453
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	13,361
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	16,814
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 8,646
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	72,332
Office Building [Member] | 12348 High Bluff Drive, Del Mar, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 1,629
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	3,096
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	6,144
Real Estate and Accumulated Depreciation, Carrying Amount of Land	1,629
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	9,240
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	10,869
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 5,760
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	38,806
Office Building [Member] | 12400 High Bluff Drive, Del Mar, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 15,167
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	40,497
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	14,337
Real Estate and Accumulated Depreciation, Carrying Amount of Land	15,167
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	54,834
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	70,001
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 25,468
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	209,220
Office Building [Member] | 3579 Valley Centre Drive, Del Mar, California One [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 2,167
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	6,897
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	7,461
Real Estate and Accumulated Depreciation, Carrying Amount of Land	2,858
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	13,667
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	16,525
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 8,977
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	52,418
Office Building [Member] | 3611 Valey Centre Dr., Del Mar, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 4,184
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	19,352
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	18,843
Real Estate and Accumulated Depreciation, Carrying Amount of Land	5,259
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	37,120
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	42,379
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 22,592
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	129,656
Office Building [Member] | 3661 Valley Centre Drive, Del Mar, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 4,038
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	21,144
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	15,535
Real Estate and Accumulated Depreciation, Carrying Amount of Land	4,725
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	35,992
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	40,717
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 18,966
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	128,364
Office Building [Member] | 3721 Valley Centre Drive, Del Mar, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 4,297
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	18,967
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	14,557
Real Estate and Accumulated Depreciation, Carrying Amount of Land	4,254
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	33,567
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	37,821
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 14,278
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	115,193
Office Building [Member] | 3811 Valley Centre Drive, Del Mar, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 3,452
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	16,152
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	20,092
Real Estate and Accumulated Depreciation, Carrying Amount of Land	4,457
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	35,239
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	39,696
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 20,243
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	112,067
Office Building [Member] | 12770 El Camino Real, Del Mar, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 9,360
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	0
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	31,914
Real Estate and Accumulated Depreciation, Carrying Amount of Land	9,360
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	31,914
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	41,274
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 830
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	73,032
Office Building [Member] | 12780 El Camino Real, Del Mar, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 18,398
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	54,954
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	2,382
Real Estate and Accumulated Depreciation, Carrying Amount of Land	18,398
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	57,336
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	75,734
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 9,642
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	140,591
Office Building [Member] | 12790 El Camino Real, Del Mar, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 10,252
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	21,236
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	1,426
Real Estate and Accumulated Depreciation, Carrying Amount of Land	10,252
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	22,662
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	32,914
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 3,788
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	78,836
Office Building [Member] | 13280 Evening Creek Drive, South I-15 Corridor, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 3,701
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	8,398
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	4,597
Real Estate and Accumulated Depreciation, Carrying Amount of Land	3,701
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	12,995
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	16,696
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 4,544
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	41,196
Office Building [Member] | 13290 Evening Creek Drive, South I-15 Corridor, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 5,229
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	11,871
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	5,919
Real Estate and Accumulated Depreciation, Carrying Amount of Land	5,229
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	17,790
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	23,019
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 5,105
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	61,180
Office Building [Member] | 13480 Evening Creek Drive, North I-15 Corridor, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 7,997
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	0
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	48,184
Real Estate and Accumulated Depreciation, Carrying Amount of Land	7,997
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	48,184
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	56,181
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 16,885
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	149,817
Office Building [Member] | 13500 Evening Creek Drive, North I-15 Corridor, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 7,581
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	35,903
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	8,761
Real Estate and Accumulated Depreciation, Carrying Amount of Land	7,580
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	44,665
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	52,245
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 18,895
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	147,533
Office Building [Member] | 13520 Evening Creek Drive, North I-15 Corridor, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 7,581
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	35,903
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	13,232
Real Estate and Accumulated Depreciation, Carrying Amount of Land	7,580
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	49,136
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	56,716
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 20,855
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	141,129
Office Building [Member] | 2305 Historic Decatur Road, San Diego, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 5,240
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	22,220
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	7,309
Real Estate and Accumulated Depreciation, Carrying Amount of Land	5,240
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	29,529
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	34,769
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 7,695
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	103,900
Office Building [Member] | 4690 Executive Dr., University Towne Centre, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 1,623
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	7,926
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	3,670
Real Estate and Accumulated Depreciation, Carrying Amount of Land	1,623
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	11,596
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	13,219
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 6,819
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	47,846
Office Building [Member] | Bohannon Drive 4100, Menlo Park, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 4,835
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	15,526
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	505
Real Estate and Accumulated Depreciation, Carrying Amount of Land	4,860
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	16,006
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	20,866
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 3,352
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	47,379
Office Building [Member] | Bohannon Drive 4200, Menlo Park, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 4,798
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	15,406
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	2,343
Real Estate and Accumulated Depreciation, Carrying Amount of Land	4,662
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	17,885
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	22,547
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 4,165
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	45,451
Office Building [Member] | Bohannon Drive 4300, Menlo Park, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 6,527
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	20,958
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	2,963
Real Estate and Accumulated Depreciation, Carrying Amount of Land	6,470
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	23,978
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	30,448
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 6,140
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	63,079
Office Building [Member] | Bohannon Drive 4400, Menlo Park, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 4,798
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	15,406
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	2,530
Real Estate and Accumulated Depreciation, Carrying Amount of Land	4,939
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	17,795
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	22,734
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 4,321
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	48,146
Office Building [Member] | Bohannon Drive 4500, Menlo Park, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 6,527
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	20,957
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	1,757
Real Estate and Accumulated Depreciation, Carrying Amount of Land	6,470
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	22,771
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	29,241
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 4,795
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	63,078
Office Building [Member] | Bohannon Drive 4600, Menlo Park, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 4,798
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	15,406
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	3,266
Real Estate and Accumulated Depreciation, Carrying Amount of Land	4,939
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	18,531
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	23,470
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 4,177
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	48,147
Office Building [Member] | Bohannon Drive 4700, Menlo Park, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 6,527
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	20,958
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	1,412
Real Estate and Accumulated Depreciation, Carrying Amount of Land	6,470
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	22,427
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	28,897
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 4,658
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	63,078
Office Building [Member] | 1290-1300 Terra Bella Avenue, Mountain View, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 28,730
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	27,555
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	0
Real Estate and Accumulated Depreciation, Carrying Amount of Land	28,730
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	27,555
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	56,285
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 2,198
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	114,175
Office Building [Member] | Fairchild Drive, 331, Mountain View, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 18,396
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	17,712
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	7,958
Real Estate and Accumulated Depreciation, Carrying Amount of Land	18,396
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	25,670
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	44,066
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 3,772
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	87,147
Office Building [Member] | 680 E Middlefield Road, Mountain View, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 34,605
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	0
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	56,464
Real Estate and Accumulated Depreciation, Carrying Amount of Land	34,605
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	56,464
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	91,069
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 6,003
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	170,090
Office Building [Member] | 690 E Middlefield Road, Mountain View, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 34,755
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	0
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	56,707
Real Estate and Accumulated Depreciation, Carrying Amount of Land	34,755
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	56,707
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	91,462
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 6,029
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	170,823
Office Building [Member] | 1701 Page Mill Rd, Palo Alto, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 0
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	99,522
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	0
Real Estate and Accumulated Depreciation, Carrying Amount of Land	0
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	99,522
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	99,522
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 3,000
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	128,688
Office Building [Member] | 3150 Porter Drive, Palo Alto, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 0
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	21,715
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	0
Real Estate and Accumulated Depreciation, Carrying Amount of Land	0
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	21,715
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	21,715
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 796
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	36,897
Office Building [Member] | 900 Jefferson Ave., Redwood City, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 16,668
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	0
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	109,272
Real Estate and Accumulated Depreciation, Carrying Amount of Land	18,063
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	107,877
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	125,940
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 8,114
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	228,505
Office Building [Member] | 900 Middlefield Road, Redwood City, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 7,959
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	0
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	49,713
Real Estate and Accumulated Depreciation, Carrying Amount of Land	8,626
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	49,046
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	57,672
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 3,497
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	118,764
Office Building [Member] | 303 Second Street, San Francisco, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation, amount of encumbrances
Real Estate and Accumulated Depreciation, Initial Cost of Land	63,550
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	154,153
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	56,675
Real Estate and Accumulated Depreciation, Carrying Amount of Land	63,550
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	210,828
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	274,378
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 60,664
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	740,047
Office Building [Member] | 100 First Street, San Francisco, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 49,150
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	131,238
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	35,190
Real Estate and Accumulated Depreciation, Carrying Amount of Land	49,150
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	166,428
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	215,578
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 45,677
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	467,095
Office Building [Member] | 250 Brannan Street, San Francisco, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 7,630
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	22,770
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	4,421
Real Estate and Accumulated Depreciation, Carrying Amount of Land	7,630
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	27,191
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	34,821
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 8,520
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	95,008
Office Building [Member] | 201 Third Street, San Francisco, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 19,260
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	84,018
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	57,295
Real Estate and Accumulated Depreciation, Carrying Amount of Land	19,260
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	141,313
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	160,573
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 37,393
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	346,538
Office Building [Member] | 301 Brannan Street, San Francisco, California [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 5,910
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	22,450
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	5,226
Real Estate and Accumulated Depreciation, Carrying Amount of Land	5,910
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	27,676
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	33,586
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 6,047
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	74,430
Office Building [Member] | 360 Third St., San Francisco, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 0
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	88,235
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	112,295
Real Estate and Accumulated Depreciation, Carrying Amount of Land	28,504
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	172,026
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	200,530
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 32,575
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	429,796
Office Building [Member] | 333 Brannan, San Francisco, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 18,645
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	0
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	78,078
Real Estate and Accumulated Depreciation, Carrying Amount of Land	18,645
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	78,078
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	96,723
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 4,109
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	185,602
Office Building [Member] | 350 Mission Street, San Francisco, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 52,815
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	0
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	211,581
Real Estate and Accumulated Depreciation, Carrying Amount of Land	52,815
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	211,581
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	264,396
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 11,205
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	455,340
Office Building [Member] | 1310 Chesapeake Terrace, Sunnyvale, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 16,700
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	11,020
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	486
Real Estate and Accumulated Depreciation, Carrying Amount of Land	16,700
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	11,506
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	28,206
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 1,581
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	76,244
Office Building [Member] | 1315 Chesapeake Terrace, Sunnyvale, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 12,260
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	7,930
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	463
Real Estate and Accumulated Depreciation, Carrying Amount of Land	12,260
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	8,393
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	20,653
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 1,490
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	55,635
Office Building [Member] | 1320-1324 Chesapeake Terrace, Sunnyvale, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 17,360
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	10,720
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	538
Real Estate and Accumulated Depreciation, Carrying Amount of Land	17,360
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	11,258
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	28,618
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 2,076
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	79,720
Office Building [Member] | 1325-1327 Chesapeake Terrace, Sunnyvale, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 12,610
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	8,160
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	345
Real Estate and Accumulated Depreciation, Carrying Amount of Land	12,610
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	8,505
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	21,115
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 1,516
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	55,383
Office Building [Member] | 505 Mathilda Ave., Sunnyvale, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 37,843
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	1,163
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	50,429
Real Estate and Accumulated Depreciation, Carrying Amount of Land	37,943
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	51,492
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	89,435
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 4,913
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	212,322
Office Building [Member] | 555 Mathilda Ave., Sunnyvale, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 37,843
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	1,163
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	50,426
Real Estate and Accumulated Depreciation, Carrying Amount of Land	37,943
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	51,489
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	89,432
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 4,913
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	212,322
Office Building [Member] | 605 Mathilda Ave., Sunnyvale, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 29,014
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	891
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	77,266
Real Estate and Accumulated Depreciation, Carrying Amount of Land	29,090
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	78,081
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	107,171
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 10,756
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	162,785
Office Building [Member] | 599 N. Mathilda Avenue, Sunnyvale, CA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 13,538
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	12,559
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	58
Real Estate and Accumulated Depreciation, Carrying Amount of Land	13,538
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	12,617
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	26,155
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 2,971
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	75,810
Office Building [Member] | 601 108th Avenue, Bellevue, Washington [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 0
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	214,095
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	32,822
Real Estate and Accumulated Depreciation, Carrying Amount of Land	0
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	246,917
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	246,917
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 60,705
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	488,470
Office Building [Member] | NE 4th Street 10900 Bellevue, Washington [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 25,080
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	150,877
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	24,038
Real Estate and Accumulated Depreciation, Carrying Amount of Land	25,080
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	174,915
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	199,995
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 38,829
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	416,755
Office Building [Member] | 10210 NE Points Dr., Kirkland, Washington [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 4,336
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	24,187
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	3,072
Real Estate and Accumulated Depreciation, Carrying Amount of Land	4,336
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	27,259
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	31,595
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 7,219
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	84,641
Office Building [Member] | 10220 NE Points Dr., Kirkland, WA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation, amount of encumbrances
Real Estate and Accumulated Depreciation, Initial Cost of Land	2,554
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	12,080
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	1,550
Real Estate and Accumulated Depreciation, Carrying Amount of Land	2,554
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	13,630
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	16,184
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 3,487
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	49,851
Office Building [Member] | 10230 NE Points Dr., Kirkland, WA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 5,071
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	24,694
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	6,148
Real Estate and Accumulated Depreciation, Carrying Amount of Land	5,071
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	30,842
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	35,913
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 7,680
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	98,982
Office Building [Member] | 3933 Lake WA Blvd. NE, Kirkland, WA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 2,380
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	15,114
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	6,591
Real Estate and Accumulated Depreciation, Carrying Amount of Land	2,380
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	21,705
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	24,085
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 5,550
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	46,450
Office Building [Member] | 837 N. 34th St., Lake Union, WA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 0
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	37,404
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	2,555
Real Estate and Accumulated Depreciation, Carrying Amount of Land	0
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	39,959
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	39,959
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 8,291
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	111,580
Office Building [Member] | 701 N. 34th St., Lake Union, WA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation, amount of encumbrances
Real Estate and Accumulated Depreciation, Initial Cost of Land	0
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	48,027
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	5,221
Real Estate and Accumulated Depreciation, Carrying Amount of Land	0
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	53,248
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	53,248
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 11,830
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	138,994
Office Building [Member] | 801 N. 34th St., Lake Union, WA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 0
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	58,537
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	183
Real Estate and Accumulated Depreciation, Carrying Amount of Land	0
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	58,720
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	58,720
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 11,997
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	169,412
Office Building [Member] | 320 Westlake Avenue North, WA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation, amount of encumbrances	$ 76,314
Real Estate and Accumulated Depreciation, Initial Cost of Land	14,710
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	82,018
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	4,320
Real Estate and Accumulated Depreciation, Carrying Amount of Land	14,710
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	86,338
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	101,048
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 13,865
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	184,644
Office Building [Member] | 321 Terry Avenue North, Lake Union, WA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 10,430
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	60,003
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	9,935
Real Estate and Accumulated Depreciation, Carrying Amount of Land	10,430
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	69,938
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	80,368
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 10,520
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	135,755
Office Building [Member] | 401 Terry Avenue North, Lake Union, WA [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate and Accumulated Depreciation, Initial Cost of Land	$ 22,500
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	77,046
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	0
Real Estate and Accumulated Depreciation, Carrying Amount of Land	22,500
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	77,046
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	99,546
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 10,222
Real estate and accumulated depreciation, life used for depreciation	35 years
Rentable Square Feet (unaudited) | ft²	140,605
Undeveloped Land and CIP Properties [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation, amount of encumbrances	$ 0
Real Estate and Accumulated Depreciation, Initial Cost of Land	692,241
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	0
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Improvements	740,567
Real Estate and Accumulated Depreciation, Carrying Amount of Land	692,241
Real Estate and Accumulated Depreciation, Carrying Amount of Buildings and Improvements	740,567
Real Estate and Accumulated Depreciation, Carrying Amount of Land and Buildings and Improvements	1,432,808
Real Estate and Accumulated Depreciation, Accumulated Depreciation	$ 0
Rentable Square Feet (unaudited) | ft²	0

Schedule III - Real Estate a130

Schedule III - Real Estate and Accumulated Depreciation (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
SEC Schedule III, Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]
Total real estate held for investment, beginning of year	$ 7,060,754	$ 6,328,146	$ 6,057,932
Acquisitions	19,829	460,957	139,123
Improvements, etc.	533,939	386,836	536,411
Total additions during period	553,768	847,793	675,534
Cost of real estate sold	(191,610)	(68,200)	(231,984)
Properties held for sale	0	(13,193)	(160,074)
Other	(5,135)	(33,792)	(13,262)
Total deductions during period	(196,745)	(115,185)	(405,320)
Total real estate held for investment, end of year	$ 7,417,777	$ 7,060,754	$ 6,328,146

Schedule III - Real Estate a131

Schedule III - Real Estate and Accumulated Depreciation (Details 3) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
SEC Schedule III, Real Estate and Accumulated Depreciation Disclosure [Abstract]
Accumulated depreciation, beginning of year	$ 1,139,853	$ 994,241	$ 947,664
Depreciation of real estate	190,515	171,983	159,524
SEC Schedule III, Real Estate Accumulated Depreciation, Period Increase	190,515	171,983	159,524
Write-offs due to sale	(66,206)	(22,471)	(66,603)
Properties held for sale	0	(3,900)	(46,191)
Other deductions	0	0	(153)
Total deductions during period	(66,206)	(26,371)	(112,947)
Accumulated depreciation, end of year	$ 1,264,162	$ 1,139,853	$ 994,241

Schedule III - Real Estate a132

Schedule III - Real Estate and Accumulated Depreciation (Details) (Textuals) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)ft²
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation, amount of encumbrances	$ 339,395
Rentable Square Feet (unaudited) | ft²	13,720,597
Debt premium	$ 2,600
Deferred financing cost	1,200
Aggregate cost of property for federal income tax purposes	$ 6,300,000
Building [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation, life used for depreciation	35 years
Tenant Improvements [Member] | Minimum [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property depreciable lives	1 year
Tenant Improvements [Member] | Maximum [Member]
Real Estate and Accumulated Depreciation [Line Items]
Property depreciable lives	20 years
Office Building [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation, amount of encumbrances	$ 339,395
Rentable Square Feet (unaudited) | ft²	13,720,597
23925 Park Sorrento, Calabasas, California [Member] | Office Building [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation, life used for depreciation	35 years
Real estate and accumulated depreciation, amount of encumbrances
Rentable Square Feet (unaudited) | ft²	11,873
12100 W. Olympic Boulevard, Los Angeles, California [Member] | Office Building [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation, life used for depreciation	35 years
Real estate and accumulated depreciation, amount of encumbrances	$ 170,000
Rentable Square Feet (unaudited) | ft²	152,048
909 Sepulveda Boulevard, El Segundo, California [Member] | Office Building [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation, life used for depreciation	35 years
Real estate and accumulated depreciation, amount of encumbrances
Rentable Square Feet (unaudited) | ft²	244,136
2100 Colorado Avenue, Santa Monica, California [Member] | Office Building [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation, life used for depreciation	35 years
Real estate and accumulated depreciation, amount of encumbrances	$ 93,081
Rentable Square Feet (unaudited) | ft²	102,864
303 Second Street, San Francisco, California [Member] | Office Building [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation, life used for depreciation	35 years
Real estate and accumulated depreciation, amount of encumbrances
Rentable Square Feet (unaudited) | ft²	740,047
320 Westlake Avenue North, WA [Member] | Office Building [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real estate and accumulated depreciation, life used for depreciation	35 years
Real estate and accumulated depreciation, amount of encumbrances	$ 76,314
Rentable Square Feet (unaudited) | ft²	184,644