Kilroy Realty (KRC) 10-Q 30 Oct 13 2013 Q3 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
	Sep. 30, 2013	Oct. 28, 2013
Entity Registrant Name	KILROY REALTY CORP
Entity Central Index Key	1025996
Current Fiscal Year End Date	-19
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	30-Sep-13
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	Q3
Amendment Flag	FALSE
Entity Common Stock, Shares Outstanding		82,113,491
Kilroy Realty, L.P. [Member]
Entity Registrant Name	Kilroy Realty, L.P.
Entity Central Index Key	1493976
Current Fiscal Year End Date	-19
Entity Filer Category	Non-accelerated Filer
Document Type	10-Q
Document Period End Date	30-Sep-13
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	Q3
Amendment Flag	FALSE

Consolidated_Balance_Sheets_Un

Consolidated Balance Sheets (Unaudited) (USD $)	Sep. 30, 2013		Dec. 31, 2012
In Thousands, unless otherwise specified
REAL ESTATE ASSETS:
Land and improvements (Note 2)	$612,843		$612,714
Buildings and improvements (Note 2)	3,527,729		3,335,026
Undeveloped land and construction in progress (Note 2)	907,959		809,654
Total real estate held for investment	5,048,531		4,757,394
Accumulated depreciation and amortization	-781,580		-756,515
Total real estate assets held for investment, net ($119,262 and $319,770 of VIE, respectively, Note 1)	4,266,951		4,000,879
REAL ESTATE ASSETS AND OTHER ASSETS HELD FOR SALE, NET (NOTE 12)	239,411		0
CASH AND CASH EQUIVALENTS	197,150		16,700
RESTRICTED CASH (Note 1)	17,931		247,544
MARKETABLE SECURITIES (Note 11)	9,192	[1],[2]	7,435	[1],[2]
CURRENT RECEIVABLES, NET (Note 4)	11,769	[3]	9,220
DEFERRED RENT RECEIVABLES, NET (Note 4)	121,659	[4]	115,418
DEFERRED LEASING COSTS AND ACQUISITION-RELATED INTANGIBLE ASSETS, NET (Notes 2 and 3)	190,085		189,968
DEFERRED FINANCING COSTS, NET	17,809		18,971
PREPAID EXPENSES AND OTHER ASSETS, NET	17,319		9,949
TOTAL ASSETS	5,089,276		4,616,084
LIABILITIES:
Secured debt (Notes 2, 5 and 11)	563,898	[5]	561,096	[5]
Exchangeable senior notes, net (Notes 5 and 11)	167,236		163,944
Unsecured debt, net (Notes 5 and 11)	1,431,048		1,130,895
Unsecured line of credit (Notes 5 and 11)	0		185,000
Accounts payable, accrued expenses and other liabilities	210,111		154,734
Accrued distributions (Note 15)	31,479		28,924
Deferred revenue and acquisition-related intangible liabilities, net (Notes 2 and 3)	102,991		117,904
Rents received in advance and tenant security deposits	41,668		37,654
Liabilities and deferred revenue of real estate assets held for sale (Note 12)	16,751		0
Total liabilities	2,565,182		2,380,151
COMMITMENTS AND CONTINGENCIES (Note 10)
Preferred stock, $.01 par value, 30,000,000 shares authorized:
Common stock, $.01 par value, 150,000,000 shares authorized, 82,113,491 and 74,926,981 shares issued and outstanding, respectively	821		749
Additional paid-in capital	2,476,424		2,126,005
Distributions in excess of earnings	-201,048		-129,535
Total stockholders’ equity	2,468,608		2,189,630
Noncontrolling interest :
Common units of the Operating Partnership (Note 6)	50,601		46,303
Noncontrolling Interest in consolidated subsidiary (Notes 2 and 6)	4,885		0
Total noncontrolling interests	55,486		46,303
Total equity	2,524,094		2,235,933
TOTAL LIABILITIES AND EQUITY / CAPITAL	5,089,276		4,616,084
Series G Cumulative Redeemable Preferred Stock
Preferred stock, $.01 par value, 30,000,000 shares authorized:
Cumulative Redeemable Preferred stock	96,155		96,155
Series H Cumulative Redeemable Preferred Stock
Preferred stock, $.01 par value, 30,000,000 shares authorized:
Cumulative Redeemable Preferred stock	$96,256		$96,256
[1]	Based on quoted prices in active markets for identical securities.
[2]	The marketable securities are held in a limited rabbi trust.
[3]	Excludes current receivables, net related to properties held for sale at September 30, 2013.
[4]	Excludes deferred rent receivables, net related to properties held for sale at September 30, 2013.
[5]	Amounts reported include the amounts of unamortized debt premiums and discounts for the periods presented.

Consolidated_Balance_Sheets_Un1

Consolidated Balance Sheets (Unaudited) (Parenthetical) (USD $)	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Variable Interest Entity, Consolidated, Carrying Amount, Assets	$135,300,000	$337,000,000
Common stock, par value	$0.01
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	82,113,491	74,926,981
Common stock, shares outstanding	82,113,491	74,926,981
Preferred Stock [Member]
Preferred stock, par value	$0.01	$0.01
Preferred stock, shares authorized	30,000,000	30,000,000
Series G Cumulative Redeemable Preferred Stock
Preferred stock, par value	$0.01	$0.01
Preferred stock dividend rate percentage	6.88%	6.88%
Preferred stock, shares authorized	4,600,000	4,600,000
Preferred stock, shares issued	4,000,000	4,000,000
Preferred stock, shares outstanding	4,000,000	4,000,000
Preferred Stock Liquidation preference	100,000,000	100,000,000
Series H Cumulative Redeemable Preferred Stock
Preferred stock, par value	$0.01	$0.01
Preferred stock dividend rate percentage	6.38%	6.38%
Preferred stock, shares authorized	4,000,000	4,000,000
Preferred stock, shares issued	4,000,000	4,000,000
Preferred stock, shares outstanding	4,000,000	4,000,000
Preferred Stock Liquidation preference	100,000,000	100,000,000
Real Estate Investment [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	119,262,000	319,770,000
Kilroy Realty, L.P. [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	$119,262,000	$319,770,000

Consolidated_Statements_of_Equ

Consolidated Statements of Equity (Unaudited) (USD $)	Total	Total Stockholders' Equity	Preferred Stock [Member]	Common Stock [Member]	Common Stock Additional Paid-in Capital	Common Stock Distributions in Excess of Earnings	Noncontrolling Interests - Common Units of the Operating Partnership	Series A Preferred Units [Member]	Series A Preferred Units [Member]	Series A Preferred Units [Member]
In Thousands, except Share data, unless otherwise specified									Total Stockholders' Equity	Common Stock Distributions in Excess of Earnings
Beginning Balance at Dec. 31, 2011	$1,327,482	$1,293,717	$121,582	$588	$1,448,997	($277,450)	$33,765
Beginning Balance, shares at Dec. 31, 2011				58,819,717
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	83,471	81,763				81,763	1,708
Issuance of Series G and Series H Preferred stock	192,411	192,411	192,411
Redemption of Series E and Series F Preferred stock, shares			-121,582
Redemption of Preferred stock and units	-126,500	-126,500				-4,918		-2,062	-2,062	-2,062
Issuance of common stock, shares				15,813,189
Issuance of common stock	662,371	662,371		159	662,212
Issuance of share-based compensation awards, shares				62,137
Issuance of share-based compensation awards	957	957			957
Noncash amortization of share-based compensation	6,182	6,182			6,182
Repurchase of common stock and restricted stock units, shares				-22,312
Repurchase of common stock and restricted stock units	-603	-603			-603
Settlement of restricted stock units for common stock, shares				5,208
Settlement of restricted stock units for common stock value	-133	-133			-133
Exercise of stock options, net, units				5,000
Exercise of stock options, net	129	129			129
Issuance of common units	5,604						5,604
Exchange of common units of the Operating Parternship, shares				10,000
Exchange of common units of the Operating Partnership	0	231			231		-231
Adjustment for noncontrolling interest	0	-3,198			-3,198		3,198
Preferred dividends and distributions	-10,795	-10,795				-10,795
Dividends declared per common share and common unit ($1.05 per share/unit)	-77,146	-75,303				-75,303	-1,843
Ending Balance at Sep. 30, 2012	2,061,368	2,019,167	192,411	747	2,114,774	-288,765	42,201
Ending Balance, shares at Sep. 30, 2012				74,692,939
Beginning Balance at Dec. 31, 2012	2,235,933	2,189,630	192,411	749	2,126,005	-129,535	46,303
Beginning Balance, shares at Dec. 31, 2012				74,926,981
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	21,518	21,252				21,252	266
Issuance of common stock, shares				7,215,838
Issuance of common stock	349,951	349,951		72	349,879
Issuance of share-based compensation awards, shares				0
Issuance of share-based compensation awards	1,075	1,075			1,075
Noncash amortization of share-based compensation	7,096	7,096			7,096
Repurchase of common stock and restricted stock units, shares				-34,164
Repurchase of common stock and restricted stock units	-1,803	-1,803			-1,803
Settlement of restricted stock units for common stock, shares				4,363
Settlement of restricted stock units for common stock value	-10	-10			-10
Exercise of stock options, net, units				473
Exercise of stock options, net	128	128			128
Issuance of common units	4,885						4,885
Adjustment for noncontrolling interest	0	-5,946			-5,946		5,946
Preferred dividends and distributions	-9,938	-9,938				-9,938
Dividends declared per common share and common unit ($1.05 per share/unit)	-84,741	-82,827				-82,827	-1,914
Ending Balance at Sep. 30, 2013	$2,524,094	$2,468,608	$192,411	$821	$2,476,424	($201,048)	$55,486
Ending Balance, shares at Sep. 30, 2013				82,113,491

Consolidated_Statements_of_Ope

Consolidated Statements of Operations (Unaudited) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
REVENUES:
Rental income	$104,939	$90,828	$308,931	$253,599
Tenant reimbursements	9,656	8,022	28,503	21,867
Other property income (Note 10)	1,102	135	7,062	961
Total revenues	115,697	98,985	344,496	276,427
EXPENSES:
Property expenses	25,123	21,016	71,728	55,531
Real estate taxes	10,295	8,746	29,707	23,668
Provision for bad debts	124	0	219	2
Ground leases	929	859	2,665	2,276
General and administrative expenses	10,226	8,727	29,750	26,745
Acquisition-related expenses	568	556	1,387	3,897
Depreciation and amortization	47,569	41,724	141,814	109,780
Total expenses	94,834	81,628	277,270	221,899
OTHER (EXPENSES) INCOME:
Interest income and other net investment gains (Note 11)	673	330	1,084	703
Interest expense (Note 5)	-18,853	-19,854	-58,021	-60,172
Total other (expenses) income	-18,180	-19,524	-56,937	-59,469
INCOME (LOSS) FROM CONTINUING OPERATIONS	2,683	-2,167	10,289	-4,941
DISCONTINUED OPERATIONS (NOTE 12)
Income from discontinued operations (Note 10)	6,344	4,689	10,806	15,603
Net gain on dispositions of discontinued operations	0	0	423	72,809
Total income from discontinued operations	6,344	4,689	11,229	88,412
NET INCOME	9,027	2,522	21,518	83,471
Net (income) loss attributable to noncontrolling common units of the Operating Partnership	-131	67	-266	-1,708
NET INCOME ATTRIBUTABLE TO KILROY REALTY CORPORATION	8,896	2,589	21,252	81,763
PREFERRED DISTRIBUTIONS AND DIVIDENDS:
Distributions to noncontrolling cumulative redeemable preferred units of the Operating Partnership	0	-747	0	-3,541
Preferred dividends	-3,312	-2,533	-9,938	-7,254
Original issuance costs of redeemed preferred stock and preferred units	0	-2,062	0	-6,980
Total preferred distributions and dividends	-3,312	-5,342	-9,938	-17,775
NET INCOME (LOSS) AVAILABLE TO COMMON STOCKHOLDERS	$5,584	($2,753)	$11,314	$63,988
Loss from continuing operations available to common stockholders per common share - basic (Note 13)	($0.01)	($0.10)	($0.01)	($0.34)
Loss from continuing operations available to common stockholders per common share - diluted (Note 13)	($0.01)	($0.10)	($0.01)	($0.34)
Net income (loss) available to common stockholders per share - basic (Note 13)	$0.07	($0.04)	$0.13	$0.92
Net income (loss) available to common stockholders per share - diluted (Note 13)	$0.07	($0.04)	$0.13	$0.92
Weighted average common shares outstanding - basic (Note 13)	76,768,893	71,889,475	75,750,822	67,975,309
Weighted average common shares outstanding - diluted (Note 13)	76,768,893	71,889,475	75,750,822	67,975,309
Dividends declared per common share	$0.35	$0.35	$1.05	$1.05

Consolidated_Statements_of_Equ1

Consolidated Statements of Equity (Unaudited) (Parenthetical) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Statement of Stockholders' Equity [Abstract]
Dividends declared per common share	$0.35	$0.35	$1.05	$1.05

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (Unaudited) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$21,518	$83,471
Adjustments to reconcile net income to net cash provided by operating activities (including discontinued operations):
Depreciation and amortization of building and improvements and leasing costs	148,982	122,754
Increase (decrease) in provision for bad debts	196	-192
Depreciation of furniture, fixtures and equipment	1,363	896
Noncash amortization of share-based compensation awards	6,454	5,544
Noncash amortization of deferred financing costs and debt discounts and premiums	4,047	7,078
Noncash amortization of net below market rents (Note 3)	-6,015	-4,616
Net gain on dispositions of discontinued operations (Note 12)	-423	-72,809
Noncash amortization of deferred revenue related to tenant-funded tenant improvements	-7,585	-6,851
Straight-line rents	-18,188	-16,433
Net change in other operating assets	-6,435	-2,529
Net change in other operating liabilities	42,844	31,965
Insurance proceeds received for property damage	-448	-951
Net cash provided by operating activities	186,310	147,327
CASH FLOWS FROM INVESTING ACTIVITIES:
Expenditures for acquisition of operating properties (Note 2)	-202,682	-393,133
Expenditures for acquistion of development and redevelopment properties (Note 2)	13,269	163,271
Expenditures for operating properties	83,991	60,967
Expenditures for development and redevelopment properties and undeveloped land	-222,192	-52,937
Net proceeds received from dispositions of operating properties	14,409	141,810
Insurance proceeds received for property damage	448	951
Increase in acquisition-related deposits	-4,000	-8,250
Decrease (increase) in restricted cash (Note 1)	229,613	-5,526
Net cash used in investing activities	-281,664	-541,323
CASH FLOWS FROM FINANCING ACTIVITIES:
Net proceeds from issuance of common stock (Note 7)	349,951	662,371
Net proceeds from issuance of Series G and Series H preferred stock	0	192,411
Borrowings on unsecured line of credit	10,000	418,000
Repayments on unsecured line of credit	-195,000	-573,000
Proceeds from issuance of secured debt	0	97,000
Principal payments on secured debt	-91,298	-104,578
Proceeds from the issuance of unsecured debt (Note 5)	299,901	150,000
Repayments of exchangeable senior notes	0	-148,000
Financing costs	-3,975	-5,396
Repurchase of common stock and restricted stock units (Note 9)	-1,813	-736
Proceeds from exercise of stock options	128	129
Dividends and distributions paid to common stockholders and common unitholders	-82,152	-70,517
Dividends and distributions paid to preferred stockholders and preferred unitholders	-9,938	-10,852
Net cash provided by financing activities	275,804	405,332
Net increase in cash and cash equivalents	180,450	11,336
Cash and cash equivalents, beginning of period	16,700	4,777
Cash and cash equivalents, end of period	197,150	16,113
SUPPLEMENTAL CASH FLOWS INFORMATION:
Cash paid for interest, net of capitalized interest of $23,573 and $11,531 as of September 30, 2013 and 2012, respectively	47,107	49,378
NONCASH INVESTING TRANSACTIONS:
Accrual for expenditures for operating properties and development and redevelopment properties	79,866	8,299
Tenant improvements funded directly by tenants	5,750	16,303
Assumption of secured debt in connection with property acquisitions (Notes 2 and 5)	95,496	177,678
Assumption of other assets and liabilities in connection with operating and development property acquisitions, net (Note 2)	422	11,667
Contribution of land, net of related liabilities, by noncontrolling interest to consolidated subsidiary (Note 2)	4,885	0
NONCASH FINANCING TRANSACTIONS:
Accrual of dividends and distributions payable to common stockholders and common unitholders	29,378	26,782
Accrual of dividends and distributions payable to preferred stockholders and preferred unitholders	1,692	1,693
Grant date fair value of share-based compensation awards (Note 9)	10,347	30,929
Issuance of common units in the Operating Partnership in connection with an operating property acquisition	4,885	5,604
Exchange of common units of the Operating Partnership into shares of the Company's common stock	0	231
Series A Preferred Units [Member]
CASH FLOWS FROM FINANCING ACTIVITIES:
Payments for Repurchase of Redeemable Preferred Stock	0	75,000
Series E and Series F Cumulative Redeemable Preferred Stock [Member]
CASH FLOWS FROM FINANCING ACTIVITIES:
Payments for Repurchase of Redeemable Preferred Stock	0	-126,500
6255 Sunset Boulevard, Los Angeles, CA [Member]
NONCASH FINANCING TRANSACTIONS:
Issuance of common units in the Operating Partnership in connection with an operating property acquisition	$0	$5,604

Consolidated_Statements_of_Cas1

Consolidated Statements of Cash Flows (Unaudited) (Parenthetical) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Statement of Cash Flows [Abstract]
Interest Paid, Capitalized	$23,573	$11,531

Consolidated_Balance_Sheets_KI

Consolidated Balance Sheets (KILROY REALTY, L.P.) (USD $)	Sep. 30, 2013		Dec. 31, 2012
In Thousands, unless otherwise specified
REAL ESTATE ASSETS:
Buildings and improvements (Note 2)	$3,527,729		$3,335,026
Undeveloped land and construction in progress (Note 2)	907,959		809,654
Total real estate held for investment	5,048,531		4,757,394
Accumulated depreciation and amortization	-781,580		-756,515
Total real estate assets held for investment, net ($119,262 and $319,770 of VIE, respectively, Note 1)	4,266,951		4,000,879
REAL ESTATE ASSETS AND OTHER ASSETS HELD FOR SALE, NET (NOTE 12)	239,411		0
CASH AND CASH EQUIVALENTS	197,150		16,700
RESTRICTED CASH (Note 1)	17,931		247,544
MARKETABLE SECURITIES (Note 11)	9,192	[1],[2]	7,435	[1],[2]
CURRENT RECEIVABLES, NET (Note 4)	11,769	[3]	9,220
DEFERRED RENT RECEIVABLES, NET (Note 4)	121,659	[4]	115,418
DEFERRED LEASING COSTS AND ACQUISITION-RELATED INTANGIBLE ASSETS, NET (Notes 2 and 3)	190,085		189,968
DEFERRED FINANCING COSTS, NET	17,809		18,971
PREPAID EXPENSES AND OTHER ASSETS, NET	17,319		9,949
TOTAL ASSETS	5,089,276		4,616,084
LIABILITIES:
Secured debt (Notes 2, 5 and 11)	563,898	[5]	561,096	[5]
Exchangeable senior notes, net (Notes 5 and 11)	167,236		163,944
Unsecured debt, net (Notes 5 and 11)	1,431,048		1,130,895
Unsecured line of credit (Notes 5 and 11)	0		185,000
Accounts payable, accrued expenses and other liabilities	210,111		154,734
Accrued distributions (Note 15)	31,479		28,924
Deferred revenue and acquisition-related intangible liabilities, net (Notes 2 and 3)	102,991		117,904
Liabilities and deferred revenue of real estate assets held for sale (Note 12)	16,751		0
Total liabilities	2,565,182		2,380,151
COMMITMENTS AND CONTINGENCIES (Note 10)
Partners' Capital (Note 8):
TOTAL LIABILITIES AND EQUITY / CAPITAL	5,089,276		4,616,084
Kilroy Realty, L.P. [Member]
REAL ESTATE ASSETS:
Land and improvements (Note 2)	612,843		612,714
Buildings and improvements (Note 2)	3,527,729		3,335,026
Undeveloped land and construction in progress (Note 2)	907,959		809,654
Total real estate held for investment	5,048,531		4,757,394
Accumulated depreciation and amortization	781,580		-756,515
Total real estate assets held for investment, net ($119,262 and $319,770 of VIE, respectively, Note 1)	4,266,951		4,000,879
CASH AND CASH EQUIVALENTS	197,150		16,700
RESTRICTED CASH (Note 1)	17,931		247,544
MARKETABLE SECURITIES (Note 11)	9,192		7,435
CURRENT RECEIVABLES, NET (Note 4)	11,769		9,220
DEFERRED RENT RECEIVABLES, NET (Note 4)	121,659		115,418
DEFERRED LEASING COSTS AND ACQUISITION-RELATED INTANGIBLE ASSETS, NET (Notes 2 and 3)	190,085		189,968
DEFERRED FINANCING COSTS, NET	17,809		18,971
PREPAID EXPENSES AND OTHER ASSETS, NET	17,319		9,949
TOTAL ASSETS	5,089,276		4,616,084
LIABILITIES:
Secured debt (Notes 2, 5 and 11)	563,898		561,096
Exchangeable senior notes, net (Notes 5 and 11)	167,236		163,944
Unsecured debt, net (Notes 5 and 11)	1,431,048		1,130,895
Unsecured line of credit (Notes 5 and 11)	0		185,000
Accounts payable, accrued expenses and other liabilities	210,111		154,734
Accrued distributions (Note 15)	31,479		28,924
Deferred revenue and acquisition-related intangible liabilities, net (Notes 2 and 3)	102,991		117,904
Rents received in advance and tenant security deposits	41,668		37,654
Total liabilities	2,565,182		2,380,151
Partners' Capital (Note 8):
Common units, 82,113,491 and 74,926,981 held by the general partner and 1,821,503 and 1,826,503 held by common limited partners issued and outstanding, respectively	2,323,341		2,040,243
Total partners' capital	2,515,752		2,232,654
Noncontrolling interest in consolidated subsidiaries (Notes 2 and 6)	8,342		3,279
Total capital	2,524,094		2,235,933
TOTAL LIABILITIES AND EQUITY / CAPITAL	5,089,276		4,616,084
Series G Cumulative Redeemable Preferred Unit [Member] | Kilroy Realty, L.P. [Member]
Partners' Capital (Note 8):
Redeemable Preferred stock	96,155		96,155
Series H Cumulative Redeemable Preferred Unit [Member] | Kilroy Realty, L.P. [Member]
Partners' Capital (Note 8):
Redeemable Preferred stock	$96,256		$96,256
[1]	Based on quoted prices in active markets for identical securities.
[2]	The marketable securities are held in a limited rabbi trust.
[3]	Excludes current receivables, net related to properties held for sale at September 30, 2013.
[4]	Excludes deferred rent receivables, net related to properties held for sale at September 30, 2013.
[5]	Amounts reported include the amounts of unamortized debt premiums and discounts for the periods presented.

Consolidated_Balance_Sheets_KI1

Consolidated Balance Sheets (KILROY REALTY, L.P.) (Parenthetical) (Kilroy Realty, L.P. [Member], USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Dec. 31, 2012
	Common Units [Member]	Common Units [Member]	Series G Cumulative Redeemable Preferred Unit [Member]	Series G Cumulative Redeemable Preferred Unit [Member]	Series H Cumulative Redeemable Preferred Unit [Member]	Series H Cumulative Redeemable Preferred Unit [Member]
Preferred Units, Issued			4,000,000	4,000,000	4,000,000	4,000,000
Preferred Units, Outstanding			4,000,000	4,000,000	4,000,000	4,000,000
Preferred stock dividend rate percentage			6.88%	6.88%	6.38%	6.38%
Preferred Stock Liquidation preference			$100,000,000	$100,000,000	$100,000,000	$100,000,000
General partner, units issued	82,113,491	74,926,981
General partners, units outstanding	82,113,491	74,926,981
Limited partners, units issued	1,821,503	1,826,503
Common units held by limited partners	1,821,503	1,826,503

Consolidated_Statements_of_Ope1

Consolidated Statements of Operations (KILROY REALTY, L.P.) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
REVENUES:
Rental income	$104,939	$90,828	$308,931	$253,599
Tenant reimbursements	9,656	8,022	28,503	21,867
Other property income (Note 10)	1,102	135	7,062	961
Total revenues	115,697	98,985	344,496	276,427
EXPENSES:
Property expenses	25,123	21,016	71,728	55,531
Real estate taxes	10,295	8,746	29,707	23,668
Provision for bad debts	124	0	219	2
Ground leases	929	859	2,665	2,276
General and administrative expenses	10,226	8,727	29,750	26,745
Acquisition-related expenses	568	556	1,387	3,897
Depreciation and amortization	47,569	41,724	141,814	109,780
Total expenses	94,834	81,628	277,270	221,899
OTHER (EXPENSES) INCOME:
Interest income and other net investment gains (Note 11)	673	330	1,084	703
Interest expense (Note 5)	-18,853	-19,854	-58,021	-60,172
Total other (expenses) income	-18,180	-19,524	-56,937	-59,469
INCOME (LOSS) FROM CONTINUING OPERATIONS	2,683	-2,167	10,289	-4,941
DISCONTINUED OPERATIONS (NOTE 12)
Income from discontinued operations (Note 10)	6,344	4,689	10,806	15,603
Net gain on dispositions of discontinued operations	0	0	423	72,809
Total income from discontinued operations	6,344	4,689	11,229	88,412
NET INCOME	9,027	2,522	21,518	83,471
NET INCOME ATTRIBUTABLE TO KILROY REALTY CORPORATION	8,896	2,589	21,252	81,763
Preferred distributions			-9,938	-10,795
Original issuance costs of redeemed preferred units	0	-2,062	0	-6,980
Total preferred distributions	3,312	5,342	9,938	17,775
NET INCOME (LOSS) AVAILABLE TO COMMON STOCKHOLDERS	5,584	-2,753	11,314	63,988
Loss from continuing operations available to common unitholders per common unit-basic (Note 14)	($0.01)	($0.10)	($0.01)	($0.34)
Loss from continuing operations available to common unitholders per common unit-diluted (Note 14)	($0.01)	($0.10)	($0.01)	($0.34)
Net income (loss) available to common unitholders per unit-basic (Note 14)	$0.07	($0.04)	$0.13	$0.92
Net income (loss) available to common unitholders per unit-diluted (Note 14)	$0.07	($0.04)	$0.13	$0.92
Weighted average common units outstanding - basic (Note 14)	76,768,893	71,889,475	75,750,822	67,975,309
Weighted average common units outstanding - diluted (Note 14)	76,768,893	71,889,475	75,750,822	67,975,309
Kilroy Realty, L.P. [Member]
REVENUES:
Rental income	104,939	90,828	308,931	253,599
Tenant reimbursements	9,656	8,022	28,503	21,867
Other property income (Note 10)	1,102	135	7,062	961
Total revenues	115,697	98,985	344,496	276,427
EXPENSES:
Property expenses	25,123	21,016	71,728	55,531
Real estate taxes	10,295	8,746	29,707	23,668
Provision for bad debts	124	0	219	2
Ground leases	929	859	2,665	2,276
General and administrative expenses	10,226	8,727	29,750	26,745
Acquisition-related expenses	568	556	1,387	3,897
Depreciation and amortization	47,569	41,724	141,814	109,780
Total expenses	94,834	81,628	277,270	221,899
OTHER (EXPENSES) INCOME:
Interest income and other net investment gains (Note 11)	673	330	1,084	703
Interest expense (Note 5)	-18,853	-19,854	-58,021	-60,172
Total other (expenses) income	-18,180	-19,524	-56,937	-59,469
INCOME (LOSS) FROM CONTINUING OPERATIONS	2,683	-2,167	10,289	-4,941
DISCONTINUED OPERATIONS (NOTE 12)
Income from discontinued operations (Note 10)	6,344	4,689	10,806	15,603
Net gain on dispositions of discontinued operations	0	0	423	72,809
Total income from discontinued operations	6,344	4,689	11,229	88,412
NET INCOME	9,027	2,522	21,518	83,471
Net income attributable to noncontrolling interests in consolidated subsidiaries	-47	-48	-178	-144
NET INCOME ATTRIBUTABLE TO KILROY REALTY CORPORATION	8,980	2,474	21,340	83,327
Preferred distributions	-3,312	-3,280	-9,938	-10,795
Original issuance costs of redeemed preferred units	0	-2,062	0	-6,980
Total preferred distributions	3,312	5,342	9,938	17,775
NET INCOME (LOSS) AVAILABLE TO COMMON STOCKHOLDERS	$5,668	($2,868)	$11,402	$65,552
Loss from continuing operations available to common unitholders per common unit-basic (Note 14)	($0.01)	($0.10)	($0.01)	($0.34)
Loss from continuing operations available to common unitholders per common unit-diluted (Note 14)	($0.01)	($0.10)	($0.01)	($0.34)
Net income (loss) available to common unitholders per unit-basic (Note 14)	$0.07	($0.04)	$0.13	$0.92
Net income (loss) available to common unitholders per unit-diluted (Note 14)	$0.07	($0.04)	$0.13	$0.92
Weighted average common units outstanding - basic (Note 14)	78,590,396	73,680,259	77,574,907	69,717,834
Weighted average common units outstanding - diluted (Note 14)	78,590,396	73,680,259	77,574,907	69,717,834
Distributions declared per common unit	$0.35	$0.35	$1.05	$1.05

Consolidated_Statements_of_Cap

Consolidated Statements of Capital (KILROY REALTY, L.P.) (Kilroy Realty, L.P. [Member], USD $)	9 Months Ended							9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2012	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2012	Sep. 30, 2012	Sep. 30, 2012
			Total Partners Capital [Member]	Total Partners Capital [Member]	Partners Capital Preferred Units [Member]	Partners Capital Preferred Units [Member]	Partners Capital Preferred Units [Member]	Partners Capital Common Unit [Member]	Partners Capital Common Unit [Member]	Noncontrolling Interest In Consolidated Subsidiaries [Member]	Noncontrolling Interest In Consolidated Subsidiaries [Member]	Series A Preferred Units [Member]	Series A Preferred Units [Member]	Series A Preferred Units [Member]
													Total Partners Capital [Member]	Partners Capital Common Unit [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	$2,235,933	$1,327,482	$2,232,654	$1,324,841	$121,582	$192,411	$192,411	$2,040,243	$1,203,259	$3,279	$2,641
Beginning Balance units								76,753,484	60,537,848
Net income	21,518	83,471	21,340	83,327				21,340	83,327	178	144
Issuance of Series G and Series H Preferred stock		192,411		192,411	192,411
Redemption of Series E and Series F Preferred stock, shares					-121,582
Redemption of Preferred units		-126,500		-126,500					-4,918
Original issuance costs of redeemed preferred units	0	-6,980										-2,062	-2,062	-2,062
Issuance of common units								7,210,838	15,813,189
Issuance of common units	349,951	662,371	349,951	662,371				349,951	662,371
Issuance of common units in connection with an operating property acquisition, shares									118,372
Issuance of common units	4,885	5,604		5,604					5,604	4,885
Issuance of share-based compensation awards, units								0	62,137
Issuance of share-based compensation awards	1,075	957	1,075	957				1,075	957
Noncash amortization of share-based compensation	7,096	6,182	7,096	6,182				7,096	6,182
Repurchase of common units and restricted stock units, units								-34,164	-22,312
Repurchase of common units and restricted stock units	-1,803	-603	-1,803	-603				-1,803	-603
Settlement of restricted stock units, units								4,363	5,208
Settlement of restricted stock units	-10	-133	-10	-133				-10	-133
Exercise of stock options, net, units								473	5,000
Exercise of stock options, net	128	129	128	129				128	129
Preferred distributions	-9,938	-10,795	-9,938	-10,795				-9,938	-10,795
Distributions declared per common unit ($1.05 per unit)	-84,741	-77,146	-84,741	-77,146				-84,741	-77,146
Ending Balance	$2,524,094	$2,061,368	$2,515,752	$2,058,583	$192,411	$192,411	$192,411	$2,323,341	$1,866,172	$8,342	$2,785
Ending Balance units								83,934,994	76,519,442

Consolidated_Statements_of_Cap1

Consolidated Statements of Capital (KILROY REALTY, L.P.) (Parenthetical) (Kilroy Realty, L.P. [Member], USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Kilroy Realty, L.P. [Member]
Distributions Per Limited Partnership and General Partnership Unit, Outstanding, Basic	$0.35	$0.35	$1.05	$1.05

Consolidated_Statements_of_Cas2

Consolidated Statements of Cash Flows (KILROY REALTY, L.P.) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$21,518	$83,471
Adjustments to reconcile net income to net cash provided by operating activities (including discontinued operations):
Depreciation and amortization of building and improvements and leasing costs	148,982	122,754
Increase (decrease) in provision for bad debts	196	-192
Depreciation of furniture, fixtures and equipment	1,363	896
Noncash amortization of share-based compensation awards	6,454	5,544
Noncash amortization of deferred financing costs and debt discounts and premiums	4,047	7,078
Noncash amortization of net below market rents (Note 3)	-6,015	-4,616
Net gain on dispositions of discontinued operations (Note 12)	-423	-72,809
Noncash amortization of deferred revenue related to tenant-funded tenant improvements	-7,585	-6,851
Straight-line rents	-18,188	-16,433
Net change in other operating assets	-6,435	-2,529
Net change in other operating liabilities	42,844	31,965
Insurance proceeds received for property damage	-448	-951
Net cash provided by operating activities	186,310	147,327
CASH FLOWS FROM INVESTING ACTIVITIES:
Expenditures for acquisition of operating properties (Note 2)	-202,682	-393,133
Expenditures for acquistion of development and redevelopment properties (Note 2)	13,269	163,271
Expenditures for operating properties	-83,991	-60,967
Expenditures for development and redevelopment properties and undeveloped land	-222,192	-52,937
Net proceeds received from dispositions of operating properties	14,409	141,810
Insurance proceeds received for property damage	448	951
Increase in acquisition-related deposits	-4,000	-8,250
Decrease (increase) in restricted cash (Note 1)	229,613	-5,526
Net cash used in investing activities	-281,664	-541,323
CASH FLOWS FROM FINANCING ACTIVITIES:
Net proceeds from issuance of Series G and Series H preferred stock	0	192,411
Borrowings on unsecured line of credit	10,000	418,000
Repayments on unsecured line of credit	-195,000	-573,000
Proceeds from issuance of secured debt	0	97,000
Principal payments on secured debt	-91,298	-104,578
Proceeds from the issuance of unsecured debt (Note 5)	299,901	150,000
Repayments of exchangeable senior notes	0	-148,000
Financing costs	-3,975	-5,396
Repurchase of common stock and restricted stock units (Note 9)	-1,813	-736
Proceeds from exercise of stock options	128	129
Distributions paid to common unitholders	-82,152	-70,517
Distributions paid to preferred unitholders	-9,938	-10,852
Net cash provided by financing activities	275,804	405,332
Net increase in cash and cash equivalents	180,450	11,336
Cash and cash equivalents, beginning of period	16,700	4,777
Cash and cash equivalents, end of period	197,150	16,113
SUPPLEMENTAL CASH FLOWS INFORMATION:
Cash paid for interest, net of capitalized interest of $23,573 and $11,531 as of September 30, 2013 and 2012, respectively	47,107	49,378
NONCASH INVESTING TRANSACTIONS:
Accrual for expenditures for operating properties and development and redevelopment properties	79,866	8,299
Tenant improvements funded directly by tenants	5,750	16,303
Assumption of secured debt in connection with property acquisitions (Notes 2 and 5)	95,496	177,678
Assumption of other assets and liabilities in connection with operating and development property acquisitions, net (Note 2)	422	11,667
Contribution of land, net of related liabilities, by noncontrolling interest to consolidated subsidiary (Note 2)	4,885	0
NONCASH FINANCING TRANSACTIONS:
Accrual of distributions payable to common unitholders	29,378	26,782
Accrual of distributions payable to preferred unitholders	1,692	1,693
Grant date fair value of share-based compensation awards (Note 9)	10,347	30,929
Issuance of common units in the Operating Partnership in connection with an operating property acquisition	4,885	5,604
Series A Preferred Units [Member]
CASH FLOWS FROM FINANCING ACTIVITIES:
Payments for Repurchase of Redeemable Preferred Stock	0	75,000
Kilroy Realty, L.P. [Member]
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	21,518	83,471
Adjustments to reconcile net income to net cash provided by operating activities (including discontinued operations):
Depreciation and amortization of building and improvements and leasing costs	148,982	122,754
Increase (decrease) in provision for bad debts	196	-192
Depreciation of furniture, fixtures and equipment	1,363	896
Noncash amortization of share-based compensation awards	6,454	5,544
Noncash amortization of deferred financing costs and debt discounts and premiums	4,047	7,078
Noncash amortization of net below market rents (Note 3)	-6,015	-4,616
Net gain on dispositions of discontinued operations (Note 12)	-423	-72,809
Noncash amortization of deferred revenue related to tenant-funded tenant improvements	-7,585	-6,851
Straight-line rents	-18,188	-16,433
Net change in other operating assets	-6,435	-2,529
Net change in other operating liabilities	42,844	31,965
Insurance proceeds received for property damage	-448	-951
Net cash provided by operating activities	186,310	147,327
CASH FLOWS FROM INVESTING ACTIVITIES:
Expenditures for acquisition of operating properties (Note 2)	-202,682	-393,133
Expenditures for acquistion of development and redevelopment properties (Note 2)	13,269	163,271
Expenditures for operating properties	-83,991	-60,967
Expenditures for development and redevelopment properties and undeveloped land	-222,192	-52,937
Net proceeds received from dispositions of operating properties	14,409	141,810
Insurance proceeds received for property damage	448	951
Increase in acquisition-related deposits	-4,000	-8,250
Decrease (increase) in restricted cash (Note 1)	229,613	-5,526
Net cash used in investing activities	-281,664	-541,323
CASH FLOWS FROM FINANCING ACTIVITIES:
Net proceeds from issuance of common units (Note 8)	349,951	662,371
Net proceeds from issuance of Series G and Series H preferred stock	0	192,411
Borrowings on unsecured line of credit	10,000	418,000
Repayments on unsecured line of credit	-195,000	-573,000
Proceeds from issuance of secured debt	0	97,000
Principal payments on secured debt	-91,298	-104,578
Proceeds from the issuance of unsecured debt (Note 5)	299,901	150,000
Repayments of exchangeable senior notes	0	-148,000
Financing costs	-3,975	-5,396
Repurchase of common stock and restricted stock units (Note 9)	-1,813	-736
Proceeds from exercise of stock options	128	129
Distributions paid to common unitholders	-82,152	-70,517
Distributions paid to preferred unitholders	-9,938	-10,852
Net cash provided by financing activities	275,804	405,332
Net increase in cash and cash equivalents	180,450	11,336
Cash and cash equivalents, beginning of period	16,700	4,777
Cash and cash equivalents, end of period	197,150	16,113
SUPPLEMENTAL CASH FLOWS INFORMATION:
Cash paid for interest, net of capitalized interest of $23,573 and $11,531 as of September 30, 2013 and 2012, respectively	47,107	49,378
NONCASH INVESTING TRANSACTIONS:
Accrual for expenditures for operating properties and development and redevelopment properties	79,866	8,299
Tenant improvements funded directly by tenants	5,750	16,303
Assumption of secured debt in connection with property acquisitions (Notes 2 and 5)	95,496	177,678
Assumption of other assets and liabilities in connection with operating and development property acquisitions, net (Note 2)	422	11,667
NONCASH FINANCING TRANSACTIONS:
Accrual of distributions payable to common unitholders	29,378	26,782
Accrual of distributions payable to preferred unitholders	1,692	1,693
Grant date fair value of share-based compensation awards (Note 9)	10,347	30,929
Issuance of common units in the Operating Partnership in connection with an operating property acquisition	4,885	5,604
Kilroy Realty, L.P. [Member] | Series A Preferred Units [Member]
CASH FLOWS FROM FINANCING ACTIVITIES:
Payments for Repurchase of Redeemable Preferred Stock	0
Series E and Series F Cumulative Redeemable Preferred Stock [Member]
CASH FLOWS FROM FINANCING ACTIVITIES:
Payments for Repurchase of Redeemable Preferred Stock	0	-126,500
Series E and Series F Cumulative Redeemable Preferred Stock [Member] | Kilroy Realty, L.P. [Member]
CASH FLOWS FROM FINANCING ACTIVITIES:
Payments for Repurchase of Redeemable Preferred Stock	0	126,500
Series A Preferred Units [Member] | Kilroy Realty, L.P. [Member]
CASH FLOWS FROM FINANCING ACTIVITIES:
Payments for Repurchase of Redeemable Preferred Stock		$75,000

Consolidated_Statements_of_Cas3

Consolidated Statements of Cash Fiows (Kilroy Realty, L.P.) (Parenthetical) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Interest Paid, Capitalized	$23,573	$11,531
Kilroy Realty, L.P. [Member]
Interest Paid, Capitalized	$23,573	$11,531

Organization_and_Basis_of_Pres

Organization and Basis of Presentation	9 Months Ended
	Sep. 30, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Basis of Presentation	Organization and Basis of Presentation
	Organization
	Kilroy Realty Corporation (the “Company”) is a self-administered real estate investment trust (“REIT”) active in premier office 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, 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”), Kilroy Realty Finance Partnership, L.P. (the “Finance Partnership”). We 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 office properties at September 30, 2013:
		Number of		Rentable	Number of	Percentage
		Buildings		Square Feet	Tenants	Occupied
	Stabilized Office Properties (1)	103		12,536,495	654	92.2	%
	______________
	-1	Excludes 13 properties located in San Diego, California and one property in Anaheim, California that were held for sale at September 30, 2013 (see Note 12 “Discontinued Operations”).
	Our stabilized portfolio includes all of our properties with the exception of properties held for sale, undeveloped land, development and redevelopment properties currently under construction or committed for construction, and “lease-up” properties. As of September 30, 2013, our stabilized portfolio of operating properties excluded the 14 properties that were classified as held for sale as of that date. (See Note 12 for additional information). We define redevelopment properties as those projects for which we expect to spend significant development and construction costs on 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 properties we recently developed or redeveloped that have not yet reached 95% occupancy and are within one year following cessation of major construction activities. As of September 30, 2013, the following properties were excluded from our stabilized portfolio:
		Number of Properties	Estimated Rentable
			Square Feet
	Properties Held for Sale (1)	14	1,159,185
	Development properties under construction (2)	5	1,516,000
	Lease-up properties	2	508,000
	_______________
	-1	Includes 13 properties located in San Diego, California and one property in Anaheim, California (see Note 12).
	(2)    Estimated rentable square feet upon completion.
	As of September 30, 2013, 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 11 office properties located in the state of Washington.
	As of September 30, 2013, the Company owned a 97.8% common general partnership interest in the Operating Partnership. The remaining 2.2% common limited partnership interest in the Operating Partnership as of September 30, 2013 was owned by non-affiliated investors and certain of our executive officers and directors (see Note 6). Both the general and limited common partnership interests in the Operating Partnership are denominated in common units. The number of common units held by the Company is at all times 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”) (see Note 6).
	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% general partnership interest in the Finance Partnership. The Operating Partnership owns the remaining 99.0% limited partnership interest. Kilroy Services, LLC (“KSLLC”), which is a wholly-owned subsidiary of the Operating Partnership, is the entity through which we conduct substantially all of our development activities. With the exception of the Operating Partnership and Redwood City Partners, LLC (see Note 2), all of our subsidiaries are wholly-owned.
	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, KSLLC, Redwood City Partners, 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, Redwood City Partners, LLC and all wholly-owned and controlled subsidiaries of the Operating Partnership. All intercompany balances and transactions have been eliminated in the consolidated financial statements.
	The accompanying interim financial statements have been prepared by management in accordance with accounting principles generally accepted in the United States of America (“GAAP”) and in conjunction with the rules and regulations of the Securities and Exchange Commission (“SEC”). Certain information and footnote disclosures required for annual financial statements have been condensed or excluded pursuant to SEC rules and regulations. Accordingly, the interim financial statements do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, the accompanying interim financial statements reflect all adjustments of a normal and recurring nature that are considered necessary for a fair presentation of the results for the interim periods presented. However, the results of operations for the interim periods are not necessarily indicative of the results that may be expected for the year ending December 31, 2013. The interim financial statements for the Company and the Operating Partnership should be read in conjunction with the audited consolidated financial statements and notes thereto included in our annual report on Form 10-K for the year ended December 31, 2012.
	Certain amounts in the consolidated statements of operations for prior periods have been reclassified to reflect the activity of discontinued operations.
	Partially Owned Entities and Variable Interest Entities
	Our accounting policy is to consolidate entities in which we have a controlling financial interest and significant decision making control over the entities 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 also consolidate entities in which the other member has no substantive kick-out rights to remove the Company as the managing member.
	We also evaluate whether the entity is a variable interest entity (“VIE”) and whether we are the primary beneficiary. VIEs are entities in which the equity investors do not have sufficient equity at risk to finance their endeavors without additional financial support or that the holders of the equity investment at risk do not have a controlling financial interest. 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 September 30, 2013 or December 31, 2012.
	As of September 30, 2013, the consolidated financial statements of the Company and the Operating Partnership included two VIEs, in which we were deemed to be the primary beneficiary. One of the VIEs was established on June 27, 2013 (see Note 2 for additional information), and the second VIE was established during the third quarter of 2013 to facilitate a potential like-kind exchange pursuant to Section 1031 of the Code (“Section 1031 Exchanges”) to defer taxable gains on dispositions for federal and state income tax purposes. To realize the tax deferral available under a Section 1031 Exchange, the Company must complete the Section 1031 Exchanges, if any, and complete the sale of the to-be-exchanged properties within 180 days of the acquisition date
	(see Note 2). The VIE established during the third quarter of 2013 will be terminated upon the completion of the Section 1031 Exchanges or the expiration of the 180 day period, as applicable. The impact of consolidating the VIEs increased the Company’s total assets, liabilities and noncontrolling interests by approximately $135.3 million (of which $119.3 million is related to real estate held for investment on our consolidated balance sheet), $4.1 million and $4.9 million, respectively, at September 30, 2013.
	As of December 31, 2012, the consolidated financial statements of the Company and the Operating Partnership included two VIEs, in which we were deemed to be the primary beneficiary. The VIEs were established during 2012 to facilitate potential Section 1031 Exchanges to defer taxable gains on dispositions for federal and state income tax purposes. During the year ended December 31, 2012, one operating property and one development project were acquired in two separate transactions and transferred to the two special purpose VIEs to facilitate potential Section 1031 Exchanges. The impact of consolidating the VIEs increased the Company’s total assets and liabilities by approximately $337.0 million (of which $319.8 million is related to real estate held for investment on our consolidated balance sheet) and $111.1 million, respectively, at December 31, 2012. During the three months ended March 31, 2013, the Section 1031 Exchanges were completed and the VIEs were terminated. As a result, $228.3 million of restricted cash set aside at December 31, 2012 to facilitate the Section 1031 Exchanges was released from escrow.

Acquisitions

Acquisitions	9 Months Ended
	Sep. 30, 2013
Business Combinations [Abstract]
Acquisitions	Acquisitions
	Operating Properties
	During the nine months ended September 30, 2013, we acquired the four operating office properties, listed below, in two transactions from unrelated third parties. The January 2013 acquisition was funded with a portion of the remaining proceeds from the sale of our industrial portfolio that was included in restricted cash at December 31, 2012 and the assumption of existing mortgage debt (see Note 5). The September 2013 acquisition was funded with proceeds from our September 2013 equity offering (see Note 7).
	Property		Date of Acquisition	Number of	Rentable Square	Occupancy as of September 30, 2013	Purchase
				Buildings	Feet		Price
							(in millions) (1)
	320 Westlake Ave. N. and 321 Terry Ave. N. (2)(3)
	Seattle, WA		January 16, 2013	2	320,398	100.00%	$	170
	12780 and 12790 El Camino Real (4)
	San Diego, CA		September 19, 2013	2	218,940	100.00%	126.4
	Total			4	539,338		$	296.4
	_______________
	-1	Excludes acquisition-related costs and includes assumed tenant improvements.
	-2	We acquired these properties through a new special purpose entity wholly owned by the Finance Partnership.
	-3	In connection with this acquisition, we assumed secured debt with an outstanding principal balance of $83.9 million that was recorded at fair value on the acquisition date, resulting in a premium of approximately $11.6 million (see Note 5).
	-4	As of September 30, 2013, these properties, together the “Heights of Del Mar” project, are temporarily being held in a separate VIE to facilitate potential Section 1031 Exchanges (see Note 1). The $126.4 million purchase price includes $9.4 million for 4.2 acres of undeveloped land the Company acquired in connection with this acquisition.
	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 acquisition date:
		Total 2013
		Acquisitions (1)
		(in thousands)
	Assets
	Land and improvements	$	53,790
	Buildings and improvements (2)	218,211
	Undeveloped land and construction in progress (3)	9,360
	Deferred leasing costs and acquisition-related intangible assets (4)	30,789
	Total assets acquired	312,150
	Liabilities
	Deferred revenue and acquisition-related intangible liabilities (5)	4,190
	Secured debt (6)	95,496
	Accounts payable, accrued expenses and other liabilities	422
	Total liabilities assumed	100,108
	Net assets and liabilities acquired (7)	$	212,042
	_______________
	-1	The purchase price of the two acquisitions completed during the nine months ended September 30, 2013 were individually less than 5% and in aggregate less than 10% of the Company’s total assets as of September 30, 2013.
	-2	Represents buildings, building improvements and tenant improvements.
	-3	In connection with one of the acquisitions, we acquired undeveloped land of approximately 4.2 acres that was added to the Company’s future development pipeline upon acquisition.
	-4	Represents in-place leases (approximately $19.6 million with a weighted average amortization period of 4.7 years), above-market leases (approximately $3.2 million with a weighted average amortization period of 6.1 years), and leasing commissions (approximately $7.9 million with a weighted average amortization period of 5.9 years).
	-5	Represents below-market leases (approximately $4.2 million with a weighted average amortization period of 7.7 years).
	-6	Represents the mortgage loan, which includes an unamortized premium of approximately $11.6 million at the date of acquisition, assumed in connection with the properties acquired in January 2013 (see Note 5).
	-7	Reflects the purchase price net of assumed secured debt and other lease-related obligations.
	Undeveloped Land/Formation of New Consolidated Subsidiary
	On June 27, 2013, the Company entered into an agreement with an unaffiliated third party and formed a new consolidated subsidiary, Redwood City Partners, LLC. In connection with this transaction, the Company acquired a 0.35 acre land site, completing the first phase of the land assemblage for its plans to develop an approximate 300,000 square foot office project (the “Crossing 900” project) in Redwood City, California. The related assets, liabilities, and noncontrolling interest acquired in connection with this transaction are included in the consolidated financial statements as of the date of acquisition. The following table summarizes the allocation of the assets acquired and liabilities assumed at the acquisition date (in thousands):
	Assets
	Undeveloped land and construction in progress	$	11,222
	Total assets	11,222
	Liabilities
	Secured debt (1)	1,750
	Accounts payable, accrued expenses and other liabilities	1,952
	Total liabilities	3,702
	Noncontrolling interest in consolidated subsidiary	4,885
	Net assets and liabilities acquired	$	2,635
	_______________
	(1)    This note was repaid as of September 30, 2013.
	In October 2013, the Company acquired a 2.0 acre undeveloped land parcel for $17.0 million, completing the final phase of the land assemblage for the Crossing 900 project (see Note 15 for additional information).

Deferred_Leasing_Costs_and_Acq

Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, net	9 Months Ended
	Sep. 30, 2013
Intangible Assets and Liabilities Disclosure [Abstract]
Intangible Assets and Liabilities Disclosure [Text Block]	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 September 30, 2013 and December 31, 2012:
		September 30, 2013			December 31, 2012
		(in thousands)
	Deferred Leasing Costs and Acquisition-related Intangible Assets, net:
	Deferred leasing costs	$	170,609		$	168,087
	Accumulated amortization	(59,943		)	(61,443		)
	Deferred leasing costs, net	110,666			106,644
	Above-market operating leases	28,842			27,977
	Accumulated amortization	(14,038		)	(12,180		)
	Above-market operating leases, net	14,804			15,797
	In-place leases	108,612			101,061
	Accumulated amortization	(44,476		)	(34,019		)
	In-place leases, net	64,136			67,042
	Below-market ground lease obligation	490			690
	Accumulated amortization	(11		)	(205		)
	Below-market ground lease obligation, net	479			485
	Total deferred leasing costs and acquisition-related intangible assets, net	$	190,085		$	189,968
	Acquisition-related Intangible Liabilities, net: (1)
	Below-market operating leases	$	70,966		$	70,486
	Accumulated amortization	(24,074		)	(17,555		)
	Below-market operating leases, net	46,892			52,931
	Above-market ground lease obligation	6,320			6,320
	Accumulated amortization	(198		)	(122		)
	Above-market ground lease obligation, net	6,122			6,198
	Total acquisition-related intangible liabilities, net	$	53,014		$	59,129
	_______________
	-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, including amounts attributable to discontinued operations, for the three and nine months ended September 30, 2013 and 2012:
		Three Months Ended September 30,						Nine Months Ended September 30,
		2013			2012			2013			2012
		(in thousands)
	Deferred leasing costs (1)	$	6,945		$	5,238		$	20,882		$	14,126
	Above-market operating leases (2)	1,417			1,459			4,214			4,205
	In-place leases (1)	7,677			6,479			22,546			14,858
	Below-market ground lease obligation (3)	2			52			6			153
	Below-market operating leases (4)	(3,355		)	(3,487		)	(10,229		)	(8,821		)
	Above-market ground lease obligation (5)	(25		)	(25		)	(76		)	(60		)
	Total	$	12,661		$	9,716		$	37,343		$	24,461
	_______________
	-1	The amortization of deferred leasing costs and in-place leases is recorded to depreciation and amortization expense 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 September 30, 2013 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)
	Remaining 2013	$	6,384		$	1,367		$	6,549		$	2		$	(3,201	)	$	(25	)
	2014	23,533			4,837			19,053			8			(11,903		)	(101		)
	2015	19,669			3,035			12,676			8			(9,385		)	(101		)
	2016	16,920			2,007			9,445			8			(7,195		)	(101		)
	2017	14,468			1,690			7,744			8			(6,127		)	(101		)
	Thereafter	29,692			1,868			8,669			445			(9,081		)	(5,693		)
	Total	$	110,666		$	14,804		$	64,136		$	479		$	(46,892	)	$	(6,122	)
	_______________
	-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	9 Months Ended
	Sep. 30, 2013
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 September 30, 2013 and December 31, 2012:
		September 30, 2013 (1)			31-Dec-12
		(in thousands)
	Current receivables	$	14,301		$	11,801
	Allowance for uncollectible tenant receivables	(2,532		)	(2,581		)
	Current receivables, net	$	11,769		$	9,220
	_______________
	-1	Excludes current receivables, net related to properties held for sale at September 30, 2013.
	Deferred Rent Receivables, net
	Deferred rent receivables, net consisted of the following as of September 30, 2013 and December 31, 2012:
		September 30, 2013 (1)			31-Dec-12
		(in thousands)
	Deferred rent receivables	$	123,632		$	118,025
	Allowance for deferred rent receivables	(1,973		)	(2,607		)
	Deferred rent receivables, net	$	121,659		$	115,418
	_______________
	-1	Excludes deferred rent receivables, net related to properties held for sale at September 30, 2013.

Secured_and_Unsecured_Debt_of_

Secured and Unsecured Debt of the Operating Partnership (Kilroy Realty, L.P. [Member])	9 Months Ended
	Sep. 30, 2013
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 September 30, 2013 and December 31, 2012:
	Type of Debt	Annual Stated Interest Rate (1)		GAAP	Maturity Date		September 30, 2013 (3)				December 31, 2012 (3)
				Effective Rate (1)(2)
							(in thousands)
	Mortgage note payable	4.27%		4.27%	Feb-18		$	133,689			$	135,000
	Mortgage note payable (4)	4.48%		4.48%	Jul-27		97,000				97,000
	Mortgage note payable (4)(5)	6.05%		3.50%	Jun-19		93,306				—
	Mortgage note payable (6)	6.37%		3.55%	Apr-13		—				83,116
	Mortgage note payable	6.51%		6.51%	Feb-17		67,907				68,615
	Mortgage note payable (4)	5.23%		3.50%	Jan-16		55,007				56,302
	Mortgage note payable (4)	5.57%		3.25%	Feb-16		41,999				43,016
	Mortgage note payable (4)	5.09%		3.50%	Aug-15		34,979				35,379
	Mortgage note payable (4)	4.94%		4.00%	Apr-15		27,970				28,941
	Mortgage note payable	7.15%		7.15%	May-17		9,546				11,210
	Other	Various		Various	Various		2,495				2,517
	Total						$	563,898			$	561,096
	______________
	-1	All interest rates presented are fixed-rate interest rates.
	-2	This represents the rate at which interest expense is recorded for financial reporting purposes, which reflects the amortization of discounts/premiums, excluding debt issuance costs.
	-3	Amounts reported include the amounts of unamortized debt premiums and discounts for the periods presented.
	-4	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.
	-5	In January 2013, in connection with the acquisition of two office buildings in Seattle, Washington, we assumed a mortgage loan that is secured by the project. The assumed mortgage had a principal balance of $83.9 million at the acquisition date and was recorded at fair value on the date of the acquisition resulting in a premium of approximately $11.6 million. The loan requires monthly principal and interest payments based on a 6.4 year amortization period.
	-6	In January 2013, we repaid this loan prior to the stated maturity date.
	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.
	4.25% Exchangeable Senior Notes
	The table below summarizes the balance and significant terms of the Company’s 4.25% Exchangeable Notes due November 2014 (the “4.25% Exchangeable Notes”) outstanding as of September 30, 2013 and December 31, 2012.
		4.25% Exchangeable Notes
		September 30,			December 31,
		2013			2012
		(in thousands)
	Principal amount	$	172,500		$	172,500
	Unamortized discount	(5,264		)	(8,556		)
	Net carrying amount of liability component	$	167,236		$	163,944
	Carrying amount of equity component	$19,835
	Issuance date	Nov-09
	Maturity date	Nov-14
	Stated coupon rate (1)	4.25%
	Effective interest rate (2)	7.13%
	Exchange rate per $1,000 principal value of the 4.25% Exchangeable Notes, as adjusted (3)	27.8307
	Exchange price, as adjusted (3)	$35.93
	Number of shares on which the aggregate consideration to be delivered on conversion is determined (3)	4,800,796
	_______________
	-1	Interest on the 4.25% Exchangeable Notes is payable semi-annually in arrears on May 15th and November 15th of each year.
	-2	The rate at which we record interest expense for financial reporting purposes, which reflects the amortization of the discounts on the 4.25% Exchangeable Notes. This rate represents our conventional debt borrowing rate at the date of issuance.
	-3	The exchange rate, exchange price, and the number of shares to be delivered upon conversion are subject to adjustment under certain circumstances including increases in our common dividends.
	The 4.25% Exchangeable Notes are exchangeable for shares of the Company’s common stock prior to maturity only upon the occurrence of certain events. During the three and nine months ended September 30, 2013, the closing sale price per share of the common stock of the Company was more than 130% of the exchange price per share of the Company’s common stock for at least 20 trading days in the specified period. As a result, for the three month period ending December 31, 2013, the 4.25% Exchangeable Notes are exchangeable at the exchange rate stated above and may be exchangeable thereafter, if one or more of the events were again to occur during future measurement periods.
	For the three and nine months ended September 30, 2013 and 2012, the per share average trading price of the Company’s common stock on the NYSE was higher than the $35.93 exchange price for the 4.25% Exchangeable Notes, as presented below:
		Three Months Ended September 30,			Nine Months Ended September 30,
		2013		2012	2013		2012
	Per share average trading price of the Company’s common stock	$51.57		$47.56	$52.42		$45.74
	The 4.25% Exchangeable Notes were exchangeable as of September 30, 2013, and were not exchangeable as of September 30, 2012. If the Exchangeable Notes were exchangeable for all periods presented, the approximate fair value of the shares upon exchangeable at September 30, 2013 and 2012, using the per share average trading price presented in the table above, would have been as follows:
		Three Months Ended September 30,							Nine Months Ended September 30,
		2013			2012				2013				2012
		(in thousands)
	Approximate fair value of shares upon conversion	$	245,200		$	225,100			$	248,000			$	218,600
	Principal amount of the 4.25% Exchangeable Notes	172,500			172,500				172,500				172,500
	Approximate fair value in excess amount of principal amount	$	72,700		$	52,600			$	75,500			$	46,100
	See Notes 13 and 14 for a discussion of the impact of the 4.25% Exchangeable Notes on our diluted earnings per share and unit calculations for the periods presented.
	Interest Expense for the Exchangeable Notes
	The unamortized discount on the 4.25% Exchangeable Notes and the 3.25% Exchangeable Notes due April 2012 (the “3.25% Exchangeable Notes” and together with the 4.25% Exchangeable Notes, the “Exchangeable Notes”) is accreted as additional interest expense from the date of issuance through the maturity date of the applicable Exchangeable Notes. The following table summarizes the total interest expense attributable to the 4.25% Exchangeable Notes and attributable to the 3.25% Exchangeable Notes (which were repaid upon maturity in April 2012), in each case based on the respective effective interest rates, before the effect of capitalized interest, for the three and nine months ended September 30, 2013 and 2012:
		Three Months Ended September 30,							Nine Months Ended September 30,
	2013			2012				2013				2012
	(in thousands)
Contractual interest payments (1)	$	1,833		$	1,833			$	5,498			$	6,888
Amortization of discount (1)	1,116			1,041				3,291				3,993
Interest expense attributable to the Exchangeable Notes (1)	$	2,949		$	2,874			$	8,789			$	10,881
_______________
-1	The Company repaid the 3.25% Exchangeable Notes in April 2012. Interest payments and discount amortization for the three and nine months ended September 30, 2013 and three months ended September 30, 2012 are solely attributable to the 4.25% Exchangeable Notes.
Capped Call Transactions
In connection with the offering of the 4.25% Exchangeable Notes, we entered into capped call option transactions (“capped calls”) to mitigate the dilutive impact of the potential exchange of the 4.25% Exchangeable Notes. The table below summarizes our capped call option positions for the 4.25% Exchangeable Notes as of September 30, 2013 and December 31, 2012.
	4.25% Exchangeable Notes
Referenced shares of common stock	4,800,796
Exchange price including effect of capped calls	$	42.81
The capped calls are expected to terminate upon the earlier of the maturity date of the 4.25% Exchangeable Notes or upon the date upon which the 4.25% Exchangeable Notes are no longer outstanding resulting from an exchange or repurchase by us. The initial cost of capped calls were recorded as a reduction to additional paid-in capital.
Unsecured Senior Notes
In January 2013, the Operating Partnership issued unsecured senior notes in a public offering with an aggregate principal balance of $300.0 million, which is included in unsecured debt, net on our consolidated balance sheets. The unsecured senior notes, which are scheduled to mature on January 15, 2023, require semi-annual interest payments each January and July based on a stated annual interest rate of 3.80%. The unsecured senior notes are shown net of the initial issuance discount of $0.1 million on the consolidated balance sheets. The Company used a portion of the net proceeds for general corporate purposes, including the repayment of borrowings under the Operating Partnership’s revolving credit facility.
Unsecured Revolving Credit Facility
The following table summarizes the balance and terms of our revolving credit facility as of September 30, 2013 and December 31, 2012, respectively:
	September 30,			December 31,
	2013			2012
	(in thousands)
Outstanding borrowings	$	—		$	185,000
Remaining borrowing capacity	500,000			315,000
Total borrowing capacity (1)	$	500,000		$	500,000
Interest rate (2)				1.66		%
Facility fee-annual rate (3)	0.30%
Maturity date (4)	Apr-17
_______________
-1	We may elect to borrow, subject to bank approval, up to an additional $200.0 million under an accordion feature under the terms of the revolving credit facility.
-2	The revolving credit facility interest rate was calculated based on an annual rate of LIBOR plus 1.450% as of both September 30, 2013 and December 31, 2012. No interest rate is shown as of September 30, 2013 because no borrowings were outstanding.
-3	The facility fee is paid on a quarterly basis and is calculated based on the total borrowing capacity. In addition to the facility fee, from 2010 to 2012 we incurred debt origination and legal costs totaling approximately $10.2 million that are currently being amortized through the maturity date of the revolving credit facility.
-4	Under the terms of the revolving credit facility, we may exercise an option to extend the maturity date by one year.
The Company intends to borrow amounts under the revolving credit facility from time to time for general corporate purposes, to fund potential acquisitions, to finance development and redevelopment expenditures and to potentially repay long-term debt.
Debt Covenants and Restrictions
The revolving credit facility, the term loan facility, the unsecured senior notes, and certain other secured debt arrangements contain covenants and restrictions requiring us to meet certain financial ratios and reporting requirements. Some of the more restrictive financial covenants include a maximum ratio of total debt to total asset value, a minimum fixed-charge coverage ratio, a minimum unsecured debt ratio, and a minimum unencumbered asset pool debt service coverage ratio. Noncompliance with one or more of the covenants and restrictions could result in the full or partial 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 September 30, 2013.
Debt Maturities
The following table summarizes the stated debt maturities and scheduled amortization payments, excluding debt discounts and premiums, as of September 30, 2013:
Year	(in thousands)
Remaining 2013	$	2,387
2014	265,346
2015	395,104
2016	249,431
2017	71,748
Thereafter	1,169,742
Total (1)	$	2,153,758
________________________
-1	Includes gross principal balance of outstanding debt before impact of net unamortized premiums totaling approximately $8.4 million.
Capitalized Interest and Loan Fees
The following table sets forth gross interest expense reported in continuing operations, including debt discount/premium and loan cost amortization, net of capitalized interest, for the three and nine months ended September 30, 2013 and 2012. The interest expense capitalized was recorded as a cost of development and redevelopment, and increased the carrying value of undeveloped land and construction in progress.
	Three Months Ended September 30,							Nine Months Ended September 30,
	2013			2012				2013				2012
	(in thousands)
Gross interest expense	$	27,942		$	24,843			$	83,322			$	73,326
Capitalized interest	(9,089		)	(4,989		)		(25,301		)		(13,154		)
Interest expense	$	18,853		$	19,854			$	58,021			$	60,172

Noncontrolling_Interests_on_th

Noncontrolling Interests on the Company's Consolidated Financial Statements	9 Months Ended
	Sep. 30, 2013
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 97.8%, 97.6% and 97.6% common general partnership interest in the Operating Partnership as of September 30, 2013, December 31, 2012, and September 30, 2012, respectively. The remaining 2.2%, 2.4% and 2.4% common limited partnership interest as of September 30, 2013, December 31, 2012 and September 30, 2012, respectively, was owned by non-affiliate investors and certain of our executive officers and directors in the form of noncontrolling common units. There were 1,821,503, 1,826,503 and 1,826,503 common units outstanding held by these investors, executive officers and directors as of September 30, 2013, December 31, 2012 and September 30, 2012, respectively.
	The noncontrolling common units may be redeemed by unitholders for cash. We, at our option, may satisfy the cash redemption obligation with shares of the Company’s common stock on a one-for-one basis. Whether satisfied in cash or shares of the Company’s common stock, the value for each noncontrolling common unit upon redemption is the amount equal to the average of the closing quoted price per share of the Company’s common stock, par value $.01 per share, as reported on the NYSE for the ten trading days immediately preceding the applicable redemption date. The aggregate value upon redemption of the then-outstanding noncontrolling common units was $92.3 million and $85.4 million as of September 30, 2013 and December 31, 2012, 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 Subsidiary
	The noncontrolling interest in consolidated subsidiary represents the third party equity interest in Redwood City Partners, LLC (see Note 2). This noncontrolling interest was $4.9 million at September 30, 2013.

Stockholders_Equity_of_the_Com

Stockholders' Equity of the Company	9 Months Ended
	Sep. 30, 2013
Equity [Abstract]
Stockholders' Equity of the Company	Stockholders’ Equity of the Company
	Issuance of Common Stock
	In September 2013, the Company completed an underwritten public offering of 6,175,000 shares of its common stock. The net offering proceeds, after deducting underwriting discounts and commissions and offering expenses, were approximately $295.9 million. The net proceeds will be used for general corporate purposes, which may include acquiring properties (including office properties and undeveloped land), funding development and redevelopment projects, and repaying indebtedness, which may include borrowings under the operating partnership’s revolving credit facility and term loan facility.
	At-The-Market Stock Offering Program
	Under our at-the-market stock offering program, which commenced in July 2011, we may offer and sell shares of our common stock having an aggregate gross sales price of up to $200.0 million from time to time in “at-the-market” offerings. The following table sets forth information regarding sales of our common stock under our at-the-market offering program for the three and nine months ended September 30, 2013:
		Three Months Ended September 30, 2013		Nine Months Ended September 30, 2013
		(in millions, except share and per share data)
	Common shares sold during the period	226,430		1,040,838
	Weighted average price per common share	$	51.12	$	53.11
	Aggregate gross proceeds	$	11.6	$	55.3
	Aggregate net proceeds after sales agent compensation	$	11.4	$	54.4
	The proceeds from the sales were used to fund development and redevelopment expenditures and general corporate purposes. Since commencement of the program, we have sold 2,183,261 shares of common stock having an aggregate gross sales price of $105.3 million. As of September 30, 2013, shares of common stock having an aggregate gross sales price of up to $94.7 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.

Partners_Capital_of_the_Operat

Partners' Capital of the Operating Partnership	9 Months Ended
	Sep. 30, 2013
Partners' Capital Notes [Abstract]
Common Units of the Operating Partnership	Partners’ Capital of the Operating Partnership
	Issuance of Common Units
	In September 2013, the Company completed an underwritten public offering of 6,175,000 shares of its common stock (see Note 7. The net offering proceeds of approximately $295.9 million were contributed by the Company to the Operating Partnership in exchange for 6,175,000 common units.
	During the three and nine months ended September 30, 2013, the Company utilized its at-the-market stock offering program to issue 226,430 and 1,040,838 shares of common stock, respectively (see Note 7. The net offering proceeds for the three and nine months ended September 30, 2013 of approximately $11.4 million and $54.4 million, respectively, were contributed by the Company to the Operating Partnership in exchange for 226,430 and 1,040,838 common units, respectively.
	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-affiliate 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:
		September 30, 2013		December 31, 2012		September 30, 2012
	Company owned common units in the Operating Partnership	82,113,491		74,926,981		74,692,939
	Company owned general partnership interest	97.8	%	97.6	%	97.6	%
	Noncontrolling common units of the Operating Partnership	1,821,503		1,826,503		1,826,503
	Ownership interest of noncontrolling interest	2.2	%	2.4	%	2.4	%
	For a further discussion of the noncontrolling common units as of September 30, 2013 and December 31, 2012, refer to Note 6.

ShareBased_Compensation

Share-Based Compensation	9 Months Ended
	Sep. 30, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation	Share-Based Compensation
	Stockholder Approved Equity Compensation Plans
	As of September 30, 2013, we maintained one share-based incentive compensation plan, the Kilroy Realty 2006 Incentive Award Plan as amended (the “2006 Plan”). As of September 30, 2013, 28,355 shares were available for grant under the 2006 Plan. The number of shares that remains available for grant is calculated using the weighted share counting provisions set forth in the 2006 Plan, which are based on the type of awards that are granted. The maximum number of shares available for grant subject to full value awards (which generally include equity awards other than options and stock appreciation rights) was 9,711 shares as of September 30, 2013.
	On April 4, 2013, the Executive Compensation Committee of the Company’s Board of Directors granted 19,084 RSUs to the Company’s Chief Operating Officer as part of his modified employment agreement. Fifty-percent of the RSUs granted are scheduled to vest in six equal annual installments beginning on December 31, 2013 through December 31, 2018. The grant date fair value of these time-based RSUs was $0.5 million, which was based on the $53.05 closing share price of the Company’s common stock on the New York Stock Exchange on the grant date. Compensation expense will be recognized on a straight-line basis over the service vesting period for these time-based RSUs. The remaining 50% of the RSUs granted are scheduled to vest in six equal annual installments for each calendar year during 2013 through 2018 based on the achievement of certain absolute or relative total shareholder return goals measured annually or, if neither of the shareholder return hurdles are achieved for an applicable year during the performance period, those RSUs will remain eligible to vest in a subsequent year (ending in 2018) based on the achievement of a cumulative total shareholder return goal. The grant date fair value of these market measure-based RSUs was $0.4 million and was calculated using a Monte Carlo simulation pricing model based on the assumptions in the table below. The grant date fair value is allocated among each of the six annual vesting tranches for these market measure-based RSUs and compensation expense will be recognized over the service vesting period using the accelerated expense attribution method.
	The computation of expected volatility is based on a blend of the historical volatility of our shares of common stock over 12 years  as that is expected to be most consistent with future volatility and equates to a time period twice as long as the six year term of the RSUs and implied volatility data based on the observed pricing of six month publicly-traded options on our shares of common stock. The risk-free interest rate is based on the yield curve on zero-coupon U.S. Treasury STRIP securities in effect at the grant date. The expected dividend yield is estimated by examining the average of the historical dividend yield levels over the six year term of the RSUs and our current annualized dividend yield as of the grant date. The expected life of the RSUs is equal to the six year vesting period.
		April 2013 Market-Measure based RSU Grant
	Grant date fair value per share	$44.55
	Expected share price volatility	27.00%
	Risk-free interest rate	0.90%
	Dividend yield	3.60%
	Expected life	6 years
	On April 4, 2013, the terms of 61,327 time-based RSUs granted to certain officers of the Company in January 2013 were modified to include market and performance-based vesting requirements based on certain total shareholder return and FFO per share targets. The RSUs will vest in five equal annual installments over the five-years requisite service period based on the achievement of certain absolute or relative total shareholder return goals measured annually or, if neither of the shareholder return hurdles are achieved for an applicable year during the performance period, those RSUs will remain eligible to vest in a subsequent year (ending in 2018) based on the achievement of a cumulative total shareholder return goal, as well as (in each case) continued employment through the applicable vesting date. The Company’s closing stock price on the date of modification was $53.05. The compensation expense related to the modified RSUs will be recognized using the accelerated attribution expense method through the remainder of the five-year requisite service period.
	On March 30, 2012, the Executive Compensation Committee of the Company’s Board of Directors granted 103,239 RSUs to the Company’s Chief Executive Officer. The RSUs granted vest in seven equal annual installments for each calendar year during 2012 through 2018 based on the achievement of certain absolute or relative total shareholder return goals measured annually or, if neither of the shareholder return hurdles are achieved for an applicable year during the performance period, those RSUs will remain eligible to vest in a subsequent year (ending in 2018) based on the achievement of a cumulative total shareholder return goal, as well as (in each case) continued employment through the applicable vesting date.
	Summary of Market-Measure Based RSUs
	A summary of our market-measure based RSU activity from January 1, 2013 through September 30, 2013 is presented below:
		Nonvested RSUs				Vested RSUs		Total RSUs
		Amount		Weighted-Average
				Grant Date
				Fair Value
				Per Share
	Outstanding at January 1, 2013	88,491		$	41.2	14,748		103,239
	Granted	9,542		44.55		—		9,542
	Vested	—		—		—		—
	Settled	—				—		—
	Issuance of dividend equivalents	—				—		—
	Modified from time based (1)	61,327		53.05		—		61,327
	Canceled					—		—
	Outstanding as of September 30, 2013	159,360		$	45.96	14,748		174,108
	_______________
	-1	On April 4, 2013 the terms of time-based RSU’s granted to certain officers of the Company in January were modified to include market-measure and performance-based vesting requirements.
	A summary of our market-measure based RSU activity for the nine months ended September 30, 2013 and 2012 is presented below:
		RSUs Granted				RSUs Vested
	Nine months ended September 30,	Non-Vested		Weighted-Average Grant Date		Vested RSUs		Total Vest-Date Fair Value
		RSUs Issued		Fair Value				(in thousands)
				Per Share
	2013	9,542		$	44.55	—		$	—
	2012	103,239		41.2		—		—
	Summary of Time-Based RSUs
	A summary of our time-based RSU activity from January 1, 2013 through September 30, 2013 is presented below:
		Nonvested RSUs				Vested RSUs		Total RSUs
		Amount		Weighted-Average
				Grant Date
				Fair Value
				Per Share
	Outstanding at January 1, 2013	279,102		$	41.3	769,761		1,048,863
	Granted, net of forfeitures	173,758		49.45		—		173,758
	Vested	(73,574	)	38.8		73,574		—
	Settled (1)					(10,342	)	(10,342	)
	Issuance of dividend equivalents (2)					20,421		20,421
	Modified to market-measure based (3)	(61,327	)	53.05		—		(61,327	)
	Canceled (1)(4)					(3,800	)	(3,800	)
	Outstanding as of September 30, 2013	317,959		$	46.13	849,614		1,167,573
	_______________
	-1	Represents vested RSUs that are settled in cash or shares of the Company’s common stock.
	-2	RSUs issued as dividend equivalents are vested upon issuance.
	-3	During the second quarter the terms of time-based RSUs granted to certain officers of the Company in January were modified to include market-measure based vesting requirements.
	-4	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 issuance, vesting or settlement of RSUs in accordance with the terms of the 2006 Plan.
	A summary of our time-based RSU activity for the nine months ended September 30, 2013 and 2012 is presented below:
		RSUs Granted				RSUs Vested
	Nine months ended September 30,	Non-Vested		Weighted-Average Grant Date		Vested RSUs		Total Vest-Date Fair Value (1)
		RSUs Issued		Fair Value				(in thousands)
				Per Share
	2013	173,758		$	49.45	(73,574	)	$	3,677
	2012	204,829		44.34		(58,940	)	2,420
_______________
-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.
Summary of Nonvested Restricted Stock
A summary of our nonvested restricted stock activity from January 1, 2013 through September 30, 2013 is presented below:
	Non-Vested		Weighted-Average
	Restricted Stock		Grant Date
			Fair Value
			Per Share
Outstanding at January 1, 2013	95,241		$	40.42
Granted	—		—
Vested (1)	(47,291	)	39.12
Outstanding as of September 30, 2013	47,950		$	41.71
_______________
-1	The total shares vested include 20,880 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 obligations.
A summary of our nonvested and vested restricted stock activity for the nine months ended September 30, 2013 and 2012 is presented below:
	Shares Granted				Shares Vested
Nine months ended September 30,	Non-Vested		Weighted-Average Grant Date		Vested Shares		Total Fair Value at Vest Date(1)
	Shares Issued		Fair Value				(in thousands)
			Per Share
2013	—		$	—	(47,291	)	$	2,290
2012	62,137		41.84		(35,623	)	1.388
_______________
-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
A summary of our stock option activity from January 1, 2013 through September 30, 2013 is presented below:
	Number of Options		Exercise Price		Remaining Contractual Term (years)
Outstanding at January 1, 2013	1,540,000		$	42.61
Granted	—		—
Exercised	(3,000	)	42.61
Forfeited	(12,000	)	42.61
Outstanding at September 30, 2013 (1)(2)	1,525,000		$	42.61	8.4
_______________
-1	As of September 30, 2013, 305,000 of the outstanding stock options were exercisable.
-2	The total intrinsic value of options outstanding at September 30, 2013 was $11.2 million.
Share-based Compensation Cost Recorded During the Period
The total compensation cost for all share-based compensation programs was $2.5 million and $2.4 million for the three months ended September 30, 2013 and 2012, respectively, and $7.2 million and $6.2 million for the nine months ended September 30, 2013 and 2012, respectively. Of the total share-based compensation costs, $0.2 million and $0.2 million was capitalized as part of real estate assets for the three months ended September 30, 2013 and 2012, respectively, and $0.6 million and $0.7 million for the
nine months ended September 30, 2013 and 2012, respectively. As of September 30, 2013, there was approximately $27.9 million of total unrecognized compensation cost related to nonvested incentive awards granted under share-based compensation arrangements that is expected to be recognized over a weighted-average period of 2.3 years. The remaining compensation cost related to these nonvested incentive awards had been recognized in periods prior to September 30, 2013.

Commitments_and_Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2013
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies
	General
	As of September 30, 2013, we had commitments of approximately $447.7 million, excluding our ground lease commitments, for contracts and executed leases directly related to our operating and redevelopment properties. However, this amount includes the $27.5 million that we expect to pay during the fourth quarter of 2013 upon the closing of the purchase of the land underlying the ground lease at 360 Third Street in San Francisco, California. We exercised an option to acquire the land during the fourth quarter of 2012.
	Environmental Matters
	We follow the policy of monitoring our 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 the properties that would have a material adverse effect on our financial condition, results of operations, and cash flow. Further, we are not aware of any environmental liability or any unasserted claim or assessment with respect to an environmental liability that we believe would require additional disclosure or the recording of a loss contingency.
	Property Damage Settlement
	During the nine months ended September 30, 2013, we settled an outstanding matter related to property damage at one of our properties. In connection with this settlement, we received a cash payment of $5.2 million and recognized this amount in other property income during the nine months ended September 30, 2013.
	Settlement with Prior Tenant
	During the three months ended September 30, 2013, we settled an outstanding matter with a prior tenant at one of the properties disposed of in December 2012. In connection with this settlement, we received a net cash payment of $3.7 million, which is presented in Income from discontinued operations in our consolidated statements of operations for the three and nine months ended September 30, 2013.

Fair_Value_Measurements_and_Di

Fair Value Measurements and Disclosures	9 Months Ended
	Sep. 30, 2013
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 a recurring basis on our consolidated financial statements are the marketable securities related to our deferred compensation plan. The following table sets forth the fair value of our marketable securities as of September 30, 2013 and December 31, 2012:
		Fair Value (Level  1) (1)
		September 30, 2013		December 31, 2012
	Description	(in thousands)
	Marketable securities (2)	$	9,192	$	7,435
	_______________
	-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 in the consolidated statements of operations. We 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 on marketable securities recorded during the three and nine months ended September 30, 2013 and 2012:
		Three Months Ended September 30,				Nine Months Ended September 30,
		2013		2012		2013		2012
	Description	(in thousands)
	Net gain on marketable securities	$	669	$	315	$	995	$	595
	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 September 30, 2013 and December 31, 2012:
		September 30, 2013				December 31, 2012
		Carrying		Fair		Carrying		Fair
		Value		Value		Value		Value
		(in thousands)
	Liabilities
	Secured debt (1)	$	563,898	$	574,661	$	561,096	$	591,993
	Exchangeable senior notes, net (1)	167,236		178,379		163,944		181,223
	Unsecured debt, net (2)	1,431,048		1,522,228		1,130,895		1,254,047
	Unsecured line of credit (1)	—		—		185,000		185,049
	_______________
	-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.
	-2	Fair value calculated using Level I and Level II inputs. Level I inputs are based on quoted prices for identical instruments in active markets. The carrying value and fair value of the Level I instruments was $841.9 million and $932.2 million, respectively, as of September 30, 2013. The carrying value and fair value of the Level I instruments at December 31, 2012, was $573.3 million and $653.0 million, respectively. The carrying value and fair value of the Level II instruments was $589.2 million and $590.0 million, respectively, as of September 30, 2013. The carrying value and fair value of the Level II instruments at December 31, 2012, was $557.6 million and $601.0 million, respectively.

Discontinued_Operations

Discontinued Operations	9 Months Ended
	Sep. 30, 2013
Discontinued Operations and Disposal Groups [Abstract]
Discontinued Operations	Discontinued Operations
	Dispositions
	The following table summarizes the property sold during the nine months ended September 30, 2013:
	Location		Property Type		Month of Disposition		Number of Buildings		Rentable			Sales Price
									Square Feet			(in millions)
	26541 Agoura Road, Calabasas, CA		Office		June		1		90,156			$	14.7
	Properties Held for Sale
	As of September 30, 2013, the following properties were classified as held for sale:
	Location		City/Submarket		Property Type		Number of Buildings			Rentable Square Feet
	San Diego Properties, San Diego, CA (1)		I-15 Corridor/Sorrento Mesa		Office		13			1,099,395
	8101 Kaiser Boulevard, Anaheim, CA (2)		Anaheim		Office		1			59,790
	Total properties held for sale						14			1,159,185
	________________________
	-1	The San Diego Properties included the following: 4910 Directors Place, 10020 Pacific Mesa Boulevard, 6055 Lusk Avenue, 5010 and 5005 Wateridge Vista Drive, 15435 and 15445 Innovation Drive, and 15051, 15073, 15231, 15253, 15333 and 15378 Avenue of Science.
	-2	We closed on the disposition of this property on October 2, 2013. The sales price was $9.6 million.
	The major classes of assets and liabilities of the properties held for sale as of September 30, 2013 were as follows:
	Real estate assets and other assets held for sale	(in thousands)
	Land and improvements	$	54,273
	Buildings and improvements	236,792
	Undeveloped land and construction in progress	1,441
	Total real estate held for sale	292,506
	Accumulated depreciation	(70,084		)
	Total real estate held for sale, net	222,422
	Current receivables, net	303
	Deferred rent receivables, net	9,062
	Deferred leasing costs and acquisition-related intangible assets, net	6,643
	Prepaid expenses and other assets, net	981
	Real estate and other assets held for sale, net	$	239,411
	Liabilities and deferred revenue of real estate assets held for sale
	Accounts payable and other liabilities	$	2,554
	Deferred revenue and acquisition-related intangible liabilities, net	12,785
	Rents received in advance and tenant security deposits	1,412
	Liabilities and deferred revenue of real estate assets held for sale	$	16,751
	Discontinued Operations
	For the three and nine months ended September 30, 2013 and 2012, discontinued operations included the income of all properties sold and classified as held for sale during the nine months ended September 30, 2013. For the three and nine months ended September 30, 2012, discontinued operations also included the income of seven office buildings and our industrial portfolio that were sold in 2012. The following table summarizes the revenue and expense components that comprise Income from discontinued operations for the three and nine months ended September 30, 2013 and 2012:
		Three Months Ended September 30,								Nine Months Ended September 30,
		2013				2012				2013				2012
		(in thousands)
	Revenues:
	Rental income	$	6,604			$	10,522			$	18,334			$	33,105
	Tenant reimbursements	892				1,639				2,331				5,296
	Other property income	4,610				229				4,617				884
	Total revenues	12,106				12,390				25,282				39,285
	Expenses:
	Property expenses	2,020				2,044				3,920				6,287
	Real estate taxes	684				1,301				2,048				3,719
	Provision for bad debts	(23		)		(194		)		(23		)		(194		)
	Depreciation and amortization	3,081				4,550				8,531				13,870
	Total expenses	5,762				7,701				14,476				23,682
	Income from discontinued operations before net gain on dispositions	6,344				4,689				10,806				15,603
	of discontinued operations
	Net gain on dispositions of discontinued operations	—				—				423				72,809
	Total income from discontinued operations	$	6,344			$	4,689			$	11,229			$	88,412

Net_Loss_Income_Available_to_C

Net (Loss) Income Available to Common Stockholders Per Share of the Company	9 Months Ended
	Sep. 30, 2013
Earnings Per Share [Abstract]
Net Income Available to Common Stockholders Per Share of the Company	Net Income (Loss) 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 (loss) available to common stockholders for the three and nine months ended September 30, 2013 and 2012:
		Three Months Ended September 30,						Nine Months Ended September 30,
		2013			2012			2013			2012
		(in thousands, except share and
		per share amounts)
	Numerator:
	Income (loss) from continuing operations	$	2,683		$	(2,167	)	$	10,289		$	(4,941	)
	Loss (income) from continuing operations attributable to	14			179			(8		)	564
	noncontrolling common units of the Operating Partnership
	Preferred distributions and dividends	(3,312		)	(5,342		)	(9,938		)	(17,775		)
	Allocation to participating securities (1)	(450		)	(408		)	(1,292		)	(1,225		)
	Numerator for basic and diluted loss from continuing	(1,065		)	(7,738		)	(949		)	(23,377		)
	operations available to common stockholders
	Income from discontinued operations	6,344			4,689			11,229			88,412
	Income from discontinued operations attributable to	(145		)	(112		)	(258		)	(2,272		)
	noncontrolling common units of the Operating Partnership
	Numerator for basic and diluted net income (loss)	$	5,134		$	(3,161	)	$	10,022		$	62,763
	available to common stockholders
	Denominator:
	Basic weighted average vested shares outstanding	76,768,893			71,889,475			75,750,822			67,975,309
	Effect of dilutive securities – contingently issuable shares	—			—			—			—
	and stock options
	Diluted weighted average vested shares and common share	76,768,893			71,889,475			75,750,822			67,975,309
	equivalents outstanding
	Basic earnings per share:
	Loss from continuing operations available to common	$	(0.01	)	$	(0.10	)	$	(0.01	)	$	(0.34	)
	stockholders per share
	Income from discontinued operations per common share	0.08			0.06			0.14			1.26
	Net income (loss) available to common stockholders per share	$	0.07		$	(0.04	)	$	0.13		$	0.92
	Diluted earnings per share:
	Loss from continuing operations available to common	$	(0.01	)	$	(0.10	)	$	(0.01	)	$	(0.34	)
	stockholders per share
	Income from discontinued operations per common share	0.08			0.06			0.14			1.26
	Net income (loss) available to common stockholders per share	$	0.07		$	(0.04	)	$	0.13		$	0.92
	________________________
	-1	Participating securities include nonvested shares, time-based RSUs and vested market-measure RSUs.
	The impact of the contingently issuable shares, which consist of 159,360 market measure-based RSUs, the 4.25% Exchangeable Notes and 1,525,000 stock options, were not considered in our diluted earnings per share calculation for the three and nine months ended September 30, 2013 because we reported a loss from continuing operations attributable to common stockholders in the respective period and the effect was anti-dilutive. The impact of the contingently issuable shares, which consisted of 103,238 market measure-based RSUs, the Exchangeable Notes and 1,540,000 stock options was not considered in our diluted earnings per share calculation for the three and nine months ended September 30, 2012 because we reported a loss from continuing operations attributable to common stockholders and the effect was anti-dilutive. See Note 5 for additional information regarding the Exchangeable Notes and Note 9 for additional information regarding the outstanding market measure-based RSUs and stock options.

Net_Loss_Income_Available_to_C1

Net (Loss) Income Available to Common Unitholders Per Unit of the Operating Partnership	9 Months Ended
	Sep. 30, 2013
Earnings Per Unit [Abstract]
Net (Loss) Income Available to Common Unitholders per Unit of the Operating Partnership	Net Income (Loss) 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 (loss) available to common unitholders for the three and nine months ended September 30, 2013 and 2012:
		Three Months Ended September 30,						Nine Months Ended September 30,
		2013			2012			2013			2012
		(in thousands, except unit and
		per unit amounts)
	Numerator:
	Income (loss) from continuing operations	$	2,683		$	(2,167	)	$	10,289		$	(4,941	)
	Income from continuing operations attributable to	(47		)	(48		)	(178		)	(144		)
	noncontrolling interests in consolidated subsidiaries
	Preferred distributions	(3,312		)	(5,342		)	(9,938		)	(17,775		)
	Allocation to participating securities (1)	(450		)	(408		)	(1,292		)	(1,225		)
	Numerator for basic and diluted loss from continuing	(1,126		)	(7,965		)	(1,119		)	(24,085		)
	operations available to common unitholders
	Income from discontinued operations	6,344			4,689			11,229			88,412
	Numerator for basic and diluted net income (loss) available	$	5,218		$	(3,276	)	$	10,110		$	64,327
	to common unitholders
	Denominator:
	Basic weighted average vested units outstanding	78,590,396			73,680,259			77,574,907			69,717,834
	Effect of dilutive securities - contingently issuable shares	—			—			—			—
	and stock options
	Diluted weighted average vested units and common unit	78,590,396			73,680,259			77,574,907			69,717,834
	equivalents outstanding
	Basic earnings per unit:
	Loss from continuing operations available to common	$	(0.01	)	$	(0.10	)	$	(0.01	)	$	(0.34	)
	unitholders per unit
	Income from discontinued operations per common unit	0.08			0.06			0.14			1.26
	Net income (loss) available to common unitholders per unit	$	0.07		$	(0.04	)	$	0.13		$	0.92
	Diluted earnings per unit:
	Loss from continuing operations available to common	$	(0.01	)	$	(0.10	)	$	(0.01	)	$	(0.34	)
	unitholders per unit
	Income from discontinued operations per common unit	0.08			0.06			0.14			1.26
	Net income (loss) available to common unitholders per unit	$	0.07		$	(0.04	)	$	0.13		$	0.92
	________________________
	-1	Participating securities include nonvested shares, time-based RSUs and vested market-measure RSUs.
	The impact of the contingently issuable units, which consist of 159,360 market measure-based RSUs, the 4.25% Exchangeable Notes and 1,525,000 stock options, were not considered in our diluted earnings per unit calculation for the three and nine months ended September 30, 2013 because the Operating Partnership reported a loss from continuing operations attributable to common unitholders in the respective periods and the effect was anti-dilutive. The impact of the contingently issuable units, which consisted of 103,238 market measure-based RSUs, the Exchangeable Notes and 1,540,000 stock options was not considered in our diluted earnings per unit calculation for the three and nine months ended September 30, 2012 because the Operating Partnership reported a loss from continuing operations attributable to common unitholders and the effect was anti-dilutive. See Note 5 for additional information regarding the Exchangeable Notes and Note 9 for additional information regarding the outstanding market measure-based RSUs and stock options.

Subsequent_Events

Subsequent Events	9 Months Ended
	Sep. 30, 2013
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events
	On October 16, 2013, aggregate dividends, distributions, and dividend equivalents of $29.8 million were paid to common stockholders and common unitholders of record on September 30, 2013 and RSU holders on the payment date.
	In October 2013, we sold one of our office properties that was held for sale as of September 30, 2013 for $9.6 million.
	In October 2013, the Company acquired a 2.0 acre undeveloped land parcel for $17.0 million, completing the final phase of the land assemblage for the Crossing 900 project located in Redwood City, California.

Organization_and_Basis_of_Pres1

Organization and Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Consolidation Policy	The consolidated financial statements of the Company include the consolidated financial position and results of operations of the Company, the Operating Partnership, the Finance Partnership, KSLLC, Redwood City Partners, 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, Redwood City Partners, LLC and all wholly-owned and controlled subsidiaries of the Operating Partnership. All intercompany balances and transactions have been eliminated in the consolidated financial statements.
Basis of Accounting	The accompanying interim financial statements have been prepared by management in accordance with accounting principles generally accepted in the United States of America (“GAAP”) and in conjunction with the rules and regulations of the Securities and Exchange Commission (“SEC”). Certain information and footnote disclosures required for annual financial statements have been condensed or excluded pursuant to SEC rules and regulations. Accordingly, the interim financial statements do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, the accompanying interim financial statements reflect all adjustments of a normal and recurring nature that are considered necessary for a fair presentation of the results for the interim periods presented. However, the results of operations for the interim periods are not necessarily indicative of the results that may be expected for the year ending December 31, 2013. The interim financial statements for the Company and the Operating Partnership should be read in conjunction with the audited consolidated financial statements and notes thereto included in our annual report on Form 10-K for the year ended December 31, 2012.
Partially Owned Entities and Variable Interest Entities	Our accounting policy is to consolidate entities in which we have a controlling financial interest and significant decision making control over the entities 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 also consolidate entities in which the other member has no substantive kick-out rights to remove the Company as the managing member.
	We also evaluate whether the entity is a variable interest entity (“VIE”) and whether we are the primary beneficiary. VIEs are entities in which the equity investors do not have sufficient equity at risk to finance their endeavors without additional financial support or that the holders of the equity investment at risk do not have a controlling financial interest. 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 September 30, 2013 or December 31, 2012.
	As of September 30, 2013, the consolidated financial statements of the Company and the Operating Partnership included two VIEs, in which we were deemed to be the primary beneficiary. One of the VIEs was established on June 27, 2013 (see Note 2 for additional information), and the second VIE was established during the third quarter of 2013 to facilitate a potential like-kind exchange pursuant to Section 1031 of the Code (“Section 1031 Exchanges”) to defer taxable gains on dispositions for federal and state income tax purposes. To realize the tax deferral available under a Section 1031 Exchange, the Company must complete the Section 1031 Exchanges, if any, and complete the sale of the to-be-exchanged properties within 180 days of the acquisition date
	(see Note 2). The VIE established during the third quarter of 2013 will be terminated upon the completion of the Section 1031 Exchanges or the expiration of the 180 day period, as applicable. The impact of consolidating the VIEs increased the Company’s total assets, liabilities and noncontrolling interests by approximately $135.3 million (of which $119.3 million is related to real estate held for investment on our consolidated balance sheet), $4.1 million and $4.9 million, respectively, at September 30, 2013.
	As of December 31, 2012, the consolidated financial statements of the Company and the Operating Partnership included two VIEs, in which we were deemed to be the primary beneficiary. The VIEs were established during 2012 to facilitate potential Section 1031 Exchanges to defer taxable gains on dispositions for federal and state income tax purposes. During the year ended December 31, 2012, one operating property and one development project were acquired in two separate transactions and transferred to the two special purpose VIEs to facilitate potential Section 1031 Exchanges. The impact of consolidating the VIEs increased the Company’s total assets and liabilities by approximately $337.0 million (of which $319.8 million is related to real estate held for investment on our consolidated balance sheet) and $111.1 million, respectively, at December 31, 2012. During the three months ended March 31, 2013, the Section 1031 Exchanges were completed and the VIEs were terminated. As a result, $228.3 million of restricted cash set aside at December 31, 2012 to facilitate the Section 1031 Exchanges was released from escrow.

Organization_and_Basis_of_Pres2

Organization and Basis of Presentation (Tables)	9 Months Ended
	Sep. 30, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Summary of real estate properties	Our stabilized portfolio of operating properties was comprised of the following office properties at September 30, 2013:
		Number of		Rentable	Number of	Percentage
		Buildings		Square Feet	Tenants	Occupied
	Stabilized Office Properties (1)	103		12,536,495	654	92.2	%
	______________
	-1	Excludes 13 properties located in San Diego, California and one property in Anaheim, California that were held for sale at September 30, 2013 (see Note 12 “Discontinued Operations”).
	Our stabilized portfolio includes all of our properties with the exception of properties held for sale, undeveloped land, development and redevelopment properties currently under construction or committed for construction, and “lease-up” properties. As of September 30, 2013, our stabilized portfolio of operating properties excluded the 14 properties that were classified as held for sale as of that date. (See Note 12 for additional information). We define redevelopment properties as those projects for which we expect to spend significant development and construction costs on 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 properties we recently developed or redeveloped that have not yet reached 95% occupancy and are within one year following cessation of major construction activities. As of September 30, 2013, the following properties were excluded from our stabilized portfolio:
		Number of Properties	Estimated Rentable
			Square Feet
	Properties Held for Sale (1)	14	1,159,185
	Development properties under construction (2)	5	1,516,000
	Lease-up properties	2	508,000
	_______________
	-1	Includes 13 properties located in San Diego, California and one property in Anaheim, California (see Note 12).
	(2)    Estimated rentable square feet upon completion.

Acquisitions_Tables

Acquisitions (Tables)	9 Months Ended
	Sep. 30, 2013
Office Properties Acquisitions [Member]
Business Acquisition [Line Items]
Acquired operating properties from unrelated third parties	During the nine months ended September 30, 2013, we acquired the four operating office properties, listed below, in two transactions from unrelated third parties. The January 2013 acquisition was funded with a portion of the remaining proceeds from the sale of our industrial portfolio that was included in restricted cash at December 31, 2012 and the assumption of existing mortgage debt (see Note 5). The September 2013 acquisition was funded with proceeds from our September 2013 equity offering (see Note 7).
	Property		Date of Acquisition	Number of	Rentable Square	Occupancy as of September 30, 2013	Purchase
				Buildings	Feet		Price
							(in millions) (1)
	320 Westlake Ave. N. and 321 Terry Ave. N. (2)(3)
	Seattle, WA		January 16, 2013	2	320,398	100.00%	$	170
	12780 and 12790 El Camino Real (4)
	San Diego, CA		September 19, 2013	2	218,940	100.00%	126.4
	Total			4	539,338		$	296.4
	_______________
	-1	Excludes acquisition-related costs and includes assumed tenant improvements.
	-2	We acquired these properties through a new special purpose entity wholly owned by the Finance Partnership.
	-3	In connection with this acquisition, we assumed secured debt with an outstanding principal balance of $83.9 million that was recorded at fair value on the acquisition date, resulting in a premium of approximately $11.6 million (see Note 5).
	-4	As of September 30, 2013, these properties, together the “Heights of Del Mar” project, are temporarily being held in a separate VIE to facilitate potential Section 1031 Exchanges (see Note 1). The $126.4 million purchase price includes $9.4 million for 4.2 acres of undeveloped land the Company acquired in connection with this acquisition.
Fair values of assets acquired and liabilities assumed	The following table summarizes the estimated fair values of the assets acquired and liabilities assumed at the acquisition date:
		Total 2013
		Acquisitions (1)
		(in thousands)
	Assets
	Land and improvements	$	53,790
	Buildings and improvements (2)	218,211
	Undeveloped land and construction in progress (3)	9,360
	Deferred leasing costs and acquisition-related intangible assets (4)	30,789
	Total assets acquired	312,150
	Liabilities
	Deferred revenue and acquisition-related intangible liabilities (5)	4,190
	Secured debt (6)	95,496
	Accounts payable, accrued expenses and other liabilities	422
	Total liabilities assumed	100,108
	Net assets and liabilities acquired (7)	$	212,042
	_______________
	-1	The purchase price of the two acquisitions completed during the nine months ended September 30, 2013 were individually less than 5% and in aggregate less than 10% of the Company’s total assets as of September 30, 2013.
	-2	Represents buildings, building improvements and tenant improvements.
	-3	In connection with one of the acquisitions, we acquired undeveloped land of approximately 4.2 acres that was added to the Company’s future development pipeline upon acquisition.
	-4	Represents in-place leases (approximately $19.6 million with a weighted average amortization period of 4.7 years), above-market leases (approximately $3.2 million with a weighted average amortization period of 6.1 years), and leasing commissions (approximately $7.9 million with a weighted average amortization period of 5.9 years).
	-5	Represents below-market leases (approximately $4.2 million with a weighted average amortization period of 7.7 years).
	-6	Represents the mortgage loan, which includes an unamortized premium of approximately $11.6 million at the date of acquisition, assumed in connection with the properties acquired in January 2013 (see Note 5).
	-7	Reflects the purchase price net of assumed secured debt and other lease-related obligations.
Redwood City Partners, LLC [Member]
Business Acquisition [Line Items]
Fair values of assets acquired and liabilities assumed	The following table summarizes the allocation of the assets acquired and liabilities assumed at the acquisition date (in thousands):
	Assets
	Undeveloped land and construction in progress	$	11,222
	Total assets	11,222
	Liabilities
	Secured debt (1)	1,750
	Accounts payable, accrued expenses and other liabilities	1,952
	Total liabilities	3,702
	Noncontrolling interest in consolidated subsidiary	4,885
	Net assets and liabilities acquired	$	2,635
	_______________
	(1)    This note was repaid as of September 30, 2013.

Deferred_Leasing_Costs_and_Acq1

Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, net (Tables)	9 Months Ended
	Sep. 30, 2013
Intangible Assets and Liabilities Disclosure [Abstract]
Summary of identified deferred leasing costs and acquisition-related intangible assets and liabilities [Table Text Block]	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 September 30, 2013 and December 31, 2012:
		September 30, 2013			December 31, 2012
		(in thousands)
	Deferred Leasing Costs and Acquisition-related Intangible Assets, net:
	Deferred leasing costs	$	170,609		$	168,087
	Accumulated amortization	(59,943		)	(61,443		)
	Deferred leasing costs, net	110,666			106,644
	Above-market operating leases	28,842			27,977
	Accumulated amortization	(14,038		)	(12,180		)
	Above-market operating leases, net	14,804			15,797
	In-place leases	108,612			101,061
	Accumulated amortization	(44,476		)	(34,019		)
	In-place leases, net	64,136			67,042
	Below-market ground lease obligation	490			690
	Accumulated amortization	(11		)	(205		)
	Below-market ground lease obligation, net	479			485
	Total deferred leasing costs and acquisition-related intangible assets, net	$	190,085		$	189,968
	Acquisition-related Intangible Liabilities, net: (1)
	Below-market operating leases	$	70,966		$	70,486
	Accumulated amortization	(24,074		)	(17,555		)
	Below-market operating leases, net	46,892			52,931
	Above-market ground lease obligation	6,320			6,320
	Accumulated amortization	(198		)	(122		)
	Above-market ground lease obligation, net	6,122			6,198
	Total acquisition-related intangible liabilities, net	$	53,014		$	59,129
	_______________
	-1	Included in deferred revenue and acquisition-related intangible liabilities, net in the consolidated balance sheets.
Schedule Of Finite Lived Intangible Assets and Liabilities Amortization Expense [Table Text Block]	The following table sets forth amortization related to deferred leasing costs and acquisition-related intangibles, including amounts attributable to discontinued operations, for the three and nine months ended September 30, 2013 and 2012:
		Three Months Ended September 30,						Nine Months Ended September 30,
		2013			2012			2013			2012
		(in thousands)
	Deferred leasing costs (1)	$	6,945		$	5,238		$	20,882		$	14,126
	Above-market operating leases (2)	1,417			1,459			4,214			4,205
	In-place leases (1)	7,677			6,479			22,546			14,858
	Below-market ground lease obligation (3)	2			52			6			153
	Below-market operating leases (4)	(3,355		)	(3,487		)	(10,229		)	(8,821		)
	Above-market ground lease obligation (5)	(25		)	(25		)	(76		)	(60		)
	Total	$	12,661		$	9,716		$	37,343		$	24,461
	_______________
	-1	The amortization of deferred leasing costs and in-place leases is recorded to depreciation and amortization expense 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.
ScheduleofFiniteLivedIntangibleAssetsAndLiabilitiesFutureAmortizationExpense [Table Text Block]	The following table sets forth the estimated annual amortization expense related to deferred leasing costs and acquisition-related intangibles as of September 30, 2013 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)
	Remaining 2013	$	6,384		$	1,367		$	6,549		$	2		$	(3,201	)	$	(25	)
	2014	23,533			4,837			19,053			8			(11,903		)	(101		)
	2015	19,669			3,035			12,676			8			(9,385		)	(101		)
	2016	16,920			2,007			9,445			8			(7,195		)	(101		)
	2017	14,468			1,690			7,744			8			(6,127		)	(101		)
	Thereafter	29,692			1,868			8,669			445			(9,081		)	(5,693		)
	Total	$	110,666		$	14,804		$	64,136		$	479		$	(46,892	)	$	(6,122	)
	_______________
	-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)	9 Months Ended
	Sep. 30, 2013
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 September 30, 2013 and December 31, 2012:
		September 30, 2013 (1)			31-Dec-12
		(in thousands)
	Current receivables	$	14,301		$	11,801
	Allowance for uncollectible tenant receivables	(2,532		)	(2,581		)
	Current receivables, net	$	11,769		$	9,220
	_______________
	-1	Excludes current receivables, net related to properties held for sale at September 30, 2013.
Deferred Rent Receivables, net	Deferred rent receivables, net consisted of the following as of September 30, 2013 and December 31, 2012:
		September 30, 2013 (1)			31-Dec-12
		(in thousands)
	Deferred rent receivables	$	123,632		$	118,025
	Allowance for deferred rent receivables	(1,973		)	(2,607		)
	Deferred rent receivables, net	$	121,659		$	115,418
	_______________
	-1	Excludes deferred rent receivables, net related to properties held for sale at September 30, 2013.

Secured_and_Unsecured_Debt_of_1

Secured and Unsecured Debt of the Operating Partnership (Tables) (Kilroy Realty, L.P. [Member])	9 Months Ended
	Sep. 30, 2013
Debt Instrument [Line Items]
Per Share Average Trading Price Of Companys Common Stock On Stock Exchange [Tables Text Block]	For the three and nine months ended September 30, 2013 and 2012, the per share average trading price of the Company’s common stock on the NYSE was higher than the $35.93 exchange price for the 4.25% Exchangeable Notes, as presented below:
		Three Months Ended September 30,			Nine Months Ended September 30,
		2013		2012	2013		2012
	Per share average trading price of the Company’s common stock	$51.57		$47.56	$52.42		$45.74
Schedule of Debt Conversions, Fair Value Upon Conversion [Table Text Block]	The 4.25% Exchangeable Notes were exchangeable as of September 30, 2013, and were not exchangeable as of September 30, 2012. If the Exchangeable Notes were exchangeable for all periods presented, the approximate fair value of the shares upon exchangeable at September 30, 2013 and 2012, using the per share average trading price presented in the table above, would have been as follows:
		Three Months Ended September 30,							Nine Months Ended September 30,
		2013			2012				2013				2012
		(in thousands)
	Approximate fair value of shares upon conversion	$	245,200		$	225,100			$	248,000			$	218,600
	Principal amount of the 4.25% Exchangeable Notes	172,500			172,500				172,500				172,500
	Approximate fair value in excess amount of principal amount	$	72,700		$	52,600			$	75,500			$	46,100
Interest expense for the exchangeable notes	The following table summarizes the total interest expense attributable to the 4.25% Exchangeable Notes and attributable to the 3.25% Exchangeable Notes (which were repaid upon maturity in April 2012), in each case based on the respective effective interest rates, before the effect of capitalized interest, for the three and nine months ended September 30, 2013 and 2012:
		Three Months Ended September 30,							Nine Months Ended September 30,
		2013			2012				2013				2012
		(in thousands)
	Contractual interest payments (1)	$	1,833		$	1,833			$	5,498			$	6,888
	Amortization of discount (1)	1,116			1,041				3,291				3,993
	Interest expense attributable to the Exchangeable Notes (1)	$	2,949		$	2,874			$	8,789			$	10,881
	_______________
	-1	The Company repaid the 3.25% Exchangeable Notes in April 2012. Interest payments and discount amortization for the three and nine months ended September 30, 2013 and three months ended September 30, 2012 are solely attributable to the 4.25% Exchangeable Notes.
Capped call Transactions	The table below summarizes our capped call option positions for the 4.25% Exchangeable Notes as of September 30, 2013 and December 31, 2012.
		4.25% Exchangeable Notes
	Referenced shares of common stock	4,800,796
	Exchange price including effect of capped calls	$	42.81
Unsecured Revolving Credit Facility	The following table summarizes the balance and terms of our revolving credit facility as of September 30, 2013 and December 31, 2012, respectively:
		September 30,			December 31,
		2013			2012
		(in thousands)
	Outstanding borrowings	$	—		$	185,000
	Remaining borrowing capacity	500,000			315,000
	Total borrowing capacity (1)	$	500,000		$	500,000
	Interest rate (2)				1.66		%
	Facility fee-annual rate (3)	0.30%
	Maturity date (4)	Apr-17
	_______________
	-1	We may elect to borrow, subject to bank approval, up to an additional $200.0 million under an accordion feature under the terms of the revolving credit facility.
	-2	The revolving credit facility interest rate was calculated based on an annual rate of LIBOR plus 1.450% as of both September 30, 2013 and December 31, 2012. No interest rate is shown as of September 30, 2013 because no borrowings were outstanding.
	-3	The facility fee is paid on a quarterly basis and is calculated based on the total borrowing capacity. In addition to the facility fee, from 2010 to 2012 we incurred debt origination and legal costs totaling approximately $10.2 million that are currently being amortized through the maturity date of the revolving credit facility.
	-4	Under the terms of the revolving credit facility, we may exercise an option to extend the maturity date by one year.
Stated debt maturities and scheduled amortization payments, excluding debt discounts	The following table summarizes the stated debt maturities and scheduled amortization payments, excluding debt discounts and premiums, as of September 30, 2013:
	Year	(in thousands)
	Remaining 2013	$	2,387
	2014	265,346
	2015	395,104
	2016	249,431
	2017	71,748
	Thereafter	1,169,742
	Total (1)	$	2,153,758
	________________________
	-1	Includes gross principal balance of outstanding debt before impact of net unamortized premiums totaling approximately $8.4 million.
Capitalized interest and loan fees	The following table sets forth gross interest expense reported in continuing operations, including debt discount/premium and loan cost amortization, net of capitalized interest, for the three and nine months ended September 30, 2013 and 2012. The interest expense capitalized was recorded as a cost of development and redevelopment, and increased the carrying value of undeveloped land and construction in progress.
		Three Months Ended September 30,							Nine Months Ended September 30,
		2013			2012				2013				2012
		(in thousands)
	Gross interest expense	$	27,942		$	24,843			$	83,322			$	73,326
	Capitalized interest	(9,089		)	(4,989		)		(25,301		)		(13,154		)
	Interest expense	$	18,853		$	19,854			$	58,021			$	60,172
Secured Debt [Member]
Debt Instrument [Line Items]
Balance and significant terms of debt	The following table sets forth the composition of our secured debt as of September 30, 2013 and December 31, 2012:
	Type of Debt	Annual Stated Interest Rate (1)		GAAP	Maturity Date		September 30, 2013 (3)				December 31, 2012 (3)
				Effective Rate (1)(2)
							(in thousands)
	Mortgage note payable	4.27%		4.27%	Feb-18		$	133,689			$	135,000
	Mortgage note payable (4)	4.48%		4.48%	Jul-27		97,000				97,000
	Mortgage note payable (4)(5)	6.05%		3.50%	Jun-19		93,306				—
	Mortgage note payable (6)	6.37%		3.55%	Apr-13		—				83,116
	Mortgage note payable	6.51%		6.51%	Feb-17		67,907				68,615
	Mortgage note payable (4)	5.23%		3.50%	Jan-16		55,007				56,302
	Mortgage note payable (4)	5.57%		3.25%	Feb-16		41,999				43,016
	Mortgage note payable (4)	5.09%		3.50%	Aug-15		34,979				35,379
	Mortgage note payable (4)	4.94%		4.00%	Apr-15		27,970				28,941
	Mortgage note payable	7.15%		7.15%	May-17		9,546				11,210
	Other	Various		Various	Various		2,495				2,517
	Total						$	563,898			$	561,096
	______________
	-1	All interest rates presented are fixed-rate interest rates.
	-2	This represents the rate at which interest expense is recorded for financial reporting purposes, which reflects the amortization of discounts/premiums, excluding debt issuance costs.
	-3	Amounts reported include the amounts of unamortized debt premiums and discounts for the periods presented.
	-4	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.
	-5	In January 2013, in connection with the acquisition of two office buildings in Seattle, Washington, we assumed a mortgage loan that is secured by the project. The assumed mortgage had a principal balance of $83.9 million at the acquisition date and was recorded at fair value on the date of the acquisition resulting in a premium of approximately $11.6 million. The loan requires monthly principal and interest payments based on a 6.4 year amortization period.
	-6	In January 2013, we repaid this loan prior to the stated maturity date.
Convertible Debt [Member]
Debt Instrument [Line Items]
Balance and significant terms of debt	The table below summarizes the balance and significant terms of the Company’s 4.25% Exchangeable Notes due November 2014 (the “4.25% Exchangeable Notes”) outstanding as of September 30, 2013 and December 31, 2012.
		4.25% Exchangeable Notes
		September 30,			December 31,
		2013			2012
		(in thousands)
	Principal amount	$	172,500		$	172,500
	Unamortized discount	(5,264		)	(8,556		)
	Net carrying amount of liability component	$	167,236		$	163,944
	Carrying amount of equity component	$19,835
	Issuance date	Nov-09
	Maturity date	Nov-14
	Stated coupon rate (1)	4.25%
	Effective interest rate (2)	7.13%
	Exchange rate per $1,000 principal value of the 4.25% Exchangeable Notes, as adjusted (3)	27.8307
	Exchange price, as adjusted (3)	$35.93
	Number of shares on which the aggregate consideration to be delivered on conversion is determined (3)	4,800,796
	_______________
	-1	Interest on the 4.25% Exchangeable Notes is payable semi-annually in arrears on May 15th and November 15th of each year.
	-2	The rate at which we record interest expense for financial reporting purposes, which reflects the amortization of the discounts on the 4.25% Exchangeable Notes. This rate represents our conventional debt borrowing rate at the date of issuance.
	-3	The exchange rate, exchange price, and the number of shares to be delivered upon conversion are subject to adjustment under certain circumstances including increases in our common dividends.

Stockholders_Equity_of_the_Com1

Stockholders' Equity of the Company (Tables)	9 Months Ended
	Sep. 30, 2013
Equity [Abstract]
Schedule of Stockholders Equity	The following table sets forth information regarding sales of our common stock under our at-the-market offering program for the three and nine months ended September 30, 2013:
		Three Months Ended September 30, 2013		Nine Months Ended September 30, 2013
		(in millions, except share and per share data)
	Common shares sold during the period	226,430		1,040,838
	Weighted average price per common share	$	51.12	$	53.11
	Aggregate gross proceeds	$	11.6	$	55.3
	Aggregate net proceeds after sales agent compensation	$	11.4	$	54.4

Partners_Capital_of_the_Operat1

Partners' Capital of the Operating Partnership Ownership Interest (Tables)	9 Months Ended
	Sep. 30, 2013
Noncontrolling Interest [Abstract]
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-affiliate 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:
		September 30, 2013		December 31, 2012		September 30, 2012
	Company owned common units in the Operating Partnership	82,113,491		74,926,981		74,692,939
	Company owned general partnership interest	97.8	%	97.6	%	97.6	%
	Noncontrolling common units of the Operating Partnership	1,821,503		1,826,503		1,826,503
	Ownership interest of noncontrolling interest	2.2	%	2.4	%	2.4	%

ShareBased_Compensation_Tables

Share-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Summary of Restricted Stock Units	A summary of our nonvested and vested restricted stock activity for the nine months ended September 30, 2013 and 2012 is presented below:
		Shares Granted				Shares Vested
	Nine months ended September 30,	Non-Vested		Weighted-Average Grant Date		Vested Shares		Total Fair Value at Vest Date(1)
		Shares Issued		Fair Value				(in thousands)
				Per Share
	2013	—		$	—	(47,291	)	$	2,290
	2012	62,137		41.84		(35,623	)	1.388
	_______________
	-1	Total fair value of shares vested was calculated based on the quoted closing share price of the Company’s common stock on the NYSE on the date of vesting.
Summary of nonvested shares	A summary of our nonvested restricted stock activity from January 1, 2013 through September 30, 2013 is presented below:
		Non-Vested		Weighted-Average
		Restricted Stock		Grant Date
				Fair Value
				Per Share
	Outstanding at January 1, 2013	95,241		$	40.42
	Granted	—		—
	Vested (1)	(47,291	)	39.12
	Outstanding as of September 30, 2013	47,950		$	41.71
	_______________
	-1	The total shares vested include 20,880 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 obligations.
Schedule of Share-based Compensation, Stock Options, Activity	A summary of our stock option activity from January 1, 2013 through September 30, 2013 is presented below:
		Number of Options		Exercise Price		Remaining Contractual Term (years)
	Outstanding at January 1, 2013	1,540,000		$	42.61
	Granted	—		—
	Exercised	(3,000	)	42.61
	Forfeited	(12,000	)	42.61
	Outstanding at September 30, 2013 (1)(2)	1,525,000		$	42.61	8.4
	_______________
	-1	As of September 30, 2013, 305,000 of the outstanding stock options were exercisable.
	-2	The total intrinsic value of options outstanding at September 30, 2013 was $11.2 million.
Market Measure-Based Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units market-measure assumptions [Table Text Block]	The expected life of the RSUs is equal to the six year vesting period.
		April 2013 Market-Measure based RSU Grant
	Grant date fair value per share	$44.55
	Expected share price volatility	27.00%
	Risk-free interest rate	0.90%
	Dividend yield	3.60%
	Expected life	6 years
Summary of Restricted Stock Units	A summary of our market-measure based RSU activity for the nine months ended September 30, 2013 and 2012 is presented below:
		RSUs Granted				RSUs Vested
	Nine months ended September 30,	Non-Vested		Weighted-Average Grant Date		Vested RSUs		Total Vest-Date Fair Value
		RSUs Issued		Fair Value				(in thousands)
				Per Share
	2013	9,542		$	44.55	—		$	—
	2012	103,239		41.2		—		—
	A summary of our market-measure based RSU activity from January 1, 2013 through September 30, 2013 is presented below:
		Nonvested RSUs				Vested RSUs		Total RSUs
		Amount		Weighted-Average
				Grant Date
				Fair Value
				Per Share
	Outstanding at January 1, 2013	88,491		$	41.2	14,748		103,239
	Granted	9,542		44.55		—		9,542
	Vested	—		—		—		—
	Settled	—				—		—
	Issuance of dividend equivalents	—				—		—
	Modified from time based (1)	61,327		53.05		—		61,327
	Canceled					—		—
	Outstanding as of September 30, 2013	159,360		$	45.96	14,748		174,108
	_______________
	-1	On April 4, 2013 the terms of time-based RSU’s granted to certain officers of the Company in January were modified to include market-measure and performance-based vesting requirements.
Time-Based Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Summary of Restricted Stock Units	A summary of our time-based RSU activity from January 1, 2013 through September 30, 2013 is presented below:
		Nonvested RSUs				Vested RSUs		Total RSUs
		Amount		Weighted-Average
				Grant Date
				Fair Value
				Per Share
	Outstanding at January 1, 2013	279,102		$	41.3	769,761		1,048,863
	Granted, net of forfeitures	173,758		49.45		—		173,758
	Vested	(73,574	)	38.8		73,574		—
	Settled (1)					(10,342	)	(10,342	)
	Issuance of dividend equivalents (2)					20,421		20,421
	Modified to market-measure based (3)	(61,327	)	53.05		—		(61,327	)
	Canceled (1)(4)					(3,800	)	(3,800	)
	Outstanding as of September 30, 2013	317,959		$	46.13	849,614		1,167,573
	_______________
	-1	Represents vested RSUs that are settled in cash or shares of the Company’s common stock.
	-2	RSUs issued as dividend equivalents are vested upon issuance.
	-3	During the second quarter the terms of time-based RSUs granted to certain officers of the Company in January were modified to include market-measure based vesting requirements.
	-4	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 issuance, vesting or settlement of RSUs in accordance with the terms of the 2006 Plan.
	A summary of our time-based RSU activity for the nine months ended September 30, 2013 and 2012 is presented below:
		RSUs Granted				RSUs Vested
	Nine months ended September 30,	Non-Vested		Weighted-Average Grant Date		Vested RSUs		Total Vest-Date Fair Value (1)
		RSUs Issued		Fair Value				(in thousands)
				Per Share
	2013	173,758		$	49.45	(73,574	)	$	3,677
	2012	204,829		44.34		(58,940	)	2,420
	_______________
	-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.

Fair_Value_Measurements_and_Di1

Fair Value Measurements and Disclosures (Tables)	9 Months Ended
	Sep. 30, 2013
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 September 30, 2013 and December 31, 2012:
		Fair Value (Level  1) (1)
		September 30, 2013		December 31, 2012
	Description	(in thousands)
	Marketable securities (2)	$	9,192	$	7,435
	_______________
	-1	Based on quoted prices in active markets for identical securities.
	-2	The marketable securities are held in a limited rabbi trust.
Fair value adjustment of marketable securities and deferred compensation plan liability	The following table sets forth the net gain on marketable securities recorded during the three and nine months ended September 30, 2013 and 2012:
		Three Months Ended September 30,				Nine Months Ended September 30,
		2013		2012		2013		2012
	Description	(in thousands)
	Net gain on marketable securities	$	669	$	315	$	995	$	595
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 September 30, 2013 and December 31, 2012:
		September 30, 2013				December 31, 2012
		Carrying		Fair		Carrying		Fair
		Value		Value		Value		Value
		(in thousands)
	Liabilities
	Secured debt (1)	$	563,898	$	574,661	$	561,096	$	591,993
	Exchangeable senior notes, net (1)	167,236		178,379		163,944		181,223
	Unsecured debt, net (2)	1,431,048		1,522,228		1,130,895		1,254,047
	Unsecured line of credit (1)	—		—		185,000		185,049
	_______________
	-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.
	-2	Fair value calculated using Level I and Level II inputs. Level I inputs are based on quoted prices for identical instruments in active markets. The carrying value and fair value of the Level I instruments was $841.9 million and $932.2 million, respectively, as of September 30, 2013. The carrying value and fair value of the Level I instruments at December 31, 2012, was $573.3 million and $653.0 million, respectively. The carrying value and fair value of the Level II instruments was $589.2 million and $590.0 million, respectively, as of September 30, 2013. The carrying value and fair value of the Level II instruments at December 31, 2012, was $557.6 million and $601.0 million, respectively.

Discontinued_Operations_Tables

Discontinued Operations (Tables)	9 Months Ended
	Sep. 30, 2013
Discontinued Operations and Disposal Groups [Abstract]
Property Sold During The Period	The following table summarizes the property sold during the nine months ended September 30, 2013:
	Location		Property Type		Month of Disposition		Number of Buildings		Rentable			Sales Price
									Square Feet			(in millions)
	26541 Agoura Road, Calabasas, CA		Office		June		1		90,156			$	14.7
Assets Held-for-sale	As of September 30, 2013, the following properties were classified as held for sale:
	Location		City/Submarket		Property Type		Number of Buildings			Rentable Square Feet
	San Diego Properties, San Diego, CA (1)		I-15 Corridor/Sorrento Mesa		Office		13			1,099,395
	8101 Kaiser Boulevard, Anaheim, CA (2)		Anaheim		Office		1			59,790
	Total properties held for sale						14			1,159,185
	________________________
	-1	The San Diego Properties included the following: 4910 Directors Place, 10020 Pacific Mesa Boulevard, 6055 Lusk Avenue, 5010 and 5005 Wateridge Vista Drive, 15435 and 15445 Innovation Drive, and 15051, 15073, 15231, 15253, 15333 and 15378 Avenue of Science.
	-2	We closed on the disposition of this property on October 2, 2013. The sales price was $9.6 million.
Schedule of Disposal Groups, Including Discontinued Operations, Income Statement, Balance Sheet and Additional Disclosures	The major classes of assets and liabilities of the properties held for sale as of September 30, 2013 were as follows:
	Real estate assets and other assets held for sale	(in thousands)
	Land and improvements	$	54,273
	Buildings and improvements	236,792
	Undeveloped land and construction in progress	1,441
	Total real estate held for sale	292,506
	Accumulated depreciation	(70,084		)
	Total real estate held for sale, net	222,422
	Current receivables, net	303
	Deferred rent receivables, net	9,062
	Deferred leasing costs and acquisition-related intangible assets, net	6,643
	Prepaid expenses and other assets, net	981
	Real estate and other assets held for sale, net	$	239,411
	Liabilities and deferred revenue of real estate assets held for sale
	Accounts payable and other liabilities	$	2,554
	Deferred revenue and acquisition-related intangible liabilities, net	12,785
	Rents received in advance and tenant security deposits	1,412
	Liabilities and deferred revenue of real estate assets held for sale	$	16,751
	The following table summarizes the revenue and expense components that comprise Income from discontinued operations for the three and nine months ended September 30, 2013 and 2012:
		Three Months Ended September 30,								Nine Months Ended September 30,
		2013				2012				2013				2012
		(in thousands)
	Revenues:
	Rental income	$	6,604			$	10,522			$	18,334			$	33,105
	Tenant reimbursements	892				1,639				2,331				5,296
	Other property income	4,610				229				4,617				884
	Total revenues	12,106				12,390				25,282				39,285
	Expenses:
	Property expenses	2,020				2,044				3,920				6,287
	Real estate taxes	684				1,301				2,048				3,719
	Provision for bad debts	(23		)		(194		)		(23		)		(194		)
	Depreciation and amortization	3,081				4,550				8,531				13,870
	Total expenses	5,762				7,701				14,476				23,682
	Income from discontinued operations before net gain on dispositions	6,344				4,689				10,806				15,603
	of discontinued operations
	Net gain on dispositions of discontinued operations	—				—				423				72,809
	Total income from discontinued operations	$	6,344			$	4,689			$	11,229			$	88,412

Net_Loss_Income_Available_to_C2

Net (Loss) Income Available to Common Stockholders Per Share of the Company (Tables)	9 Months Ended
	Sep. 30, 2013
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 (loss) available to common stockholders for the three and nine months ended September 30, 2013 and 2012:
		Three Months Ended September 30,						Nine Months Ended September 30,
		2013			2012			2013			2012
		(in thousands, except share and
		per share amounts)
	Numerator:
	Income (loss) from continuing operations	$	2,683		$	(2,167	)	$	10,289		$	(4,941	)
	Loss (income) from continuing operations attributable to	14			179			(8		)	564
	noncontrolling common units of the Operating Partnership
	Preferred distributions and dividends	(3,312		)	(5,342		)	(9,938		)	(17,775		)
	Allocation to participating securities (1)	(450		)	(408		)	(1,292		)	(1,225		)
	Numerator for basic and diluted loss from continuing	(1,065		)	(7,738		)	(949		)	(23,377		)
	operations available to common stockholders
	Income from discontinued operations	6,344			4,689			11,229			88,412
	Income from discontinued operations attributable to	(145		)	(112		)	(258		)	(2,272		)
	noncontrolling common units of the Operating Partnership
	Numerator for basic and diluted net income (loss)	$	5,134		$	(3,161	)	$	10,022		$	62,763
	available to common stockholders
	Denominator:
	Basic weighted average vested shares outstanding	76,768,893			71,889,475			75,750,822			67,975,309
	Effect of dilutive securities – contingently issuable shares	—			—			—			—
	and stock options
	Diluted weighted average vested shares and common share	76,768,893			71,889,475			75,750,822			67,975,309
	equivalents outstanding
	Basic earnings per share:
	Loss from continuing operations available to common	$	(0.01	)	$	(0.10	)	$	(0.01	)	$	(0.34	)
	stockholders per share
	Income from discontinued operations per common share	0.08			0.06			0.14			1.26
	Net income (loss) available to common stockholders per share	$	0.07		$	(0.04	)	$	0.13		$	0.92
	Diluted earnings per share:
	Loss from continuing operations available to common	$	(0.01	)	$	(0.10	)	$	(0.01	)	$	(0.34	)
	stockholders per share
	Income from discontinued operations per common share	0.08			0.06			0.14			1.26
	Net income (loss) available to common stockholders per share	$	0.07		$	(0.04	)	$	0.13		$	0.92
	________________________
	-1	Participating securities include nonvested shares, time-based RSUs and vested market-measure RSUs.

Net_Loss_Income_Available_to_C3

Net (Loss) Income Available to Common Unitholders Per Unit of the Operating Partnership (Tables)	9 Months Ended
	Sep. 30, 2013
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 (loss) available to common stockholders for the three and nine months ended September 30, 2013 and 2012:
		Three Months Ended September 30,						Nine Months Ended September 30,
		2013			2012			2013			2012
		(in thousands, except share and
		per share amounts)
	Numerator:
	Income (loss) from continuing operations	$	2,683		$	(2,167	)	$	10,289		$	(4,941	)
	Loss (income) from continuing operations attributable to	14			179			(8		)	564
	noncontrolling common units of the Operating Partnership
	Preferred distributions and dividends	(3,312		)	(5,342		)	(9,938		)	(17,775		)
	Allocation to participating securities (1)	(450		)	(408		)	(1,292		)	(1,225		)
	Numerator for basic and diluted loss from continuing	(1,065		)	(7,738		)	(949		)	(23,377		)
	operations available to common stockholders
	Income from discontinued operations	6,344			4,689			11,229			88,412
	Income from discontinued operations attributable to	(145		)	(112		)	(258		)	(2,272		)
	noncontrolling common units of the Operating Partnership
	Numerator for basic and diluted net income (loss)	$	5,134		$	(3,161	)	$	10,022		$	62,763
	available to common stockholders
	Denominator:
	Basic weighted average vested shares outstanding	76,768,893			71,889,475			75,750,822			67,975,309
	Effect of dilutive securities – contingently issuable shares	—			—			—			—
	and stock options
	Diluted weighted average vested shares and common share	76,768,893			71,889,475			75,750,822			67,975,309
	equivalents outstanding
	Basic earnings per share:
	Loss from continuing operations available to common	$	(0.01	)	$	(0.10	)	$	(0.01	)	$	(0.34	)
	stockholders per share
	Income from discontinued operations per common share	0.08			0.06			0.14			1.26
	Net income (loss) available to common stockholders per share	$	0.07		$	(0.04	)	$	0.13		$	0.92
	Diluted earnings per share:
	Loss from continuing operations available to common	$	(0.01	)	$	(0.10	)	$	(0.01	)	$	(0.34	)
	stockholders per share
	Income from discontinued operations per common share	0.08			0.06			0.14			1.26
	Net income (loss) available to common stockholders per share	$	0.07		$	(0.04	)	$	0.13		$	0.92
	________________________
	-1	Participating securities include nonvested shares, time-based RSUs and vested market-measure 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 (loss) available to common unitholders for the three and nine months ended September 30, 2013 and 2012:
		Three Months Ended September 30,						Nine Months Ended September 30,
		2013			2012			2013			2012
		(in thousands, except unit and
		per unit amounts)
	Numerator:
	Income (loss) from continuing operations	$	2,683		$	(2,167	)	$	10,289		$	(4,941	)
	Income from continuing operations attributable to	(47		)	(48		)	(178		)	(144		)
	noncontrolling interests in consolidated subsidiaries
	Preferred distributions	(3,312		)	(5,342		)	(9,938		)	(17,775		)
	Allocation to participating securities (1)	(450		)	(408		)	(1,292		)	(1,225		)
	Numerator for basic and diluted loss from continuing	(1,126		)	(7,965		)	(1,119		)	(24,085		)
	operations available to common unitholders
	Income from discontinued operations	6,344			4,689			11,229			88,412
	Numerator for basic and diluted net income (loss) available	$	5,218		$	(3,276	)	$	10,110		$	64,327
	to common unitholders
	Denominator:
	Basic weighted average vested units outstanding	78,590,396			73,680,259			77,574,907			69,717,834
	Effect of dilutive securities - contingently issuable shares	—			—			—			—
	and stock options
	Diluted weighted average vested units and common unit	78,590,396			73,680,259			77,574,907			69,717,834
	equivalents outstanding
	Basic earnings per unit:
	Loss from continuing operations available to common	$	(0.01	)	$	(0.10	)	$	(0.01	)	$	(0.34	)
	unitholders per unit
	Income from discontinued operations per common unit	0.08			0.06			0.14			1.26
	Net income (loss) available to common unitholders per unit	$	0.07		$	(0.04	)	$	0.13		$	0.92
	Diluted earnings per unit:
	Loss from continuing operations available to common	$	(0.01	)	$	(0.10	)	$	(0.01	)	$	(0.34	)
	unitholders per unit
	Income from discontinued operations per common unit	0.08			0.06			0.14			1.26
	Net income (loss) available to common unitholders per unit	$	0.07		$	(0.04	)	$	0.13		$	0.92
	________________________
	-1	Participating securities include nonvested shares, time-based RSUs and vested market-measure RSUs.

Organization_and_Basis_of_Pres3

Organization and Basis of Presentation (Details)	Sep. 30, 2013
	building
Real Estate Properties [Line Items]
Number of buildings	14
Office Properties [Member]
Real Estate Properties [Line Items]
Number of buildings	103	[1]
Rentable square feet	12,536,495	[1]
Number of Tenants	654	[1]
Percentage Occupied	92.20%	[1]
Other Segments [Member] | Properties Held for Sale [Member]
Real Estate Properties [Line Items]
Number of buildings	14	[2]
Rentable square feet	1,159,185	[2]
Other Segments [Member] | Development Properties [Member]
Real Estate Properties [Line Items]
Number of buildings	5	[3]
Rentable square feet	1,516,000	[3]
Other Segments [Member] | Lease Up Properties [Member]
Real Estate Properties [Line Items]
Number of buildings	2
Rentable square feet	508,000
San Diego, California [Member] | Other Segments [Member] | Properties Held for Sale [Member]
Real Estate Properties [Line Items]
Number of buildings	13	[3],[4]
Anaheim, California [Member] | Other Segments [Member] | Properties Held for Sale [Member]
Real Estate Properties [Line Items]
Number of buildings	1	[3],[5]
[1]	Excludes 13 properties located in San Diego, California and one property in Anaheim, California that were held for sale at September 30, 2013 (see Note 12 “Discontinued Operations”).
[2]	Includes 13 properties located in San Diego, California and one property in Anaheim, California (see Note 12).
[3]	Estimated rentable square feet upon completion.
[4]	The San Diego Properties included the following: 4910 Directors Place, 10020 Pacific Mesa Boulevard, 6055 Lusk Avenue, 5010 and 5005 Wateridge Vista Drive, 15435 and 15445 Innovation Drive, and 15051, 15073, 15231, 15253, 15333 and 15378 Avenue of Science.
[5]	We closed on the disposition of this property on October 2, 2013. The sales price was $9.6 million.

Organization_and_Basis_of_Pres4

Organization and Basis of Presentation (Details Textuals) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013		Sep. 30, 2013		Sep. 30, 2012	Dec. 31, 2012
	building		building			entity
	entity		entity
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Stabilized Occupancy	95.00%
Percentage of general partnership interest owned by the company in the Operating Partnership	97.80%		97.80%		97.60%	97.60%
Percentage of Common limited partnership interest owned by certain non-affiliated investors and certain directors and officers of the Company in the Operating Partnership	2.20%		2.20%		2.40%	2.40%
Number of buildings	14		14
Number of VIE's	2		2			2
VIE Assets	$135,300,000		$135,300,000			$337,000,000
VIE Liabilities	4,100,000		4,100,000			111,100,000
Impact of VIE to Noncontrolling interest	4,885,000		4,885,000			0
Restricted cash	228,300,000		229,613,000		-5,526,000
WASHINGTON
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of buildings	11		11
Kilroy Realty, L.P. [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%
Percentage of limited partnership interest owned by Operating Partnership	99.00%
Properties Held for Sale [Member] | Other Segments [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of buildings	14	[1]	14	[1]
Properties Held for Sale [Member] | Other Segments [Member] | San Diego, California [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of buildings	13	[2],[3]	13	[2],[3]
Properties Held for Sale [Member] | Other Segments [Member] | Anaheim, California [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of buildings	1	[2],[4]	1	[2],[4]
Real Estate Investment [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
VIE Assets	$119,262,000		$119,262,000			$319,770,000
[1]	Includes 13 properties located in San Diego, California and one property in Anaheim, California (see Note 12).
[2]	Estimated rentable square feet upon completion.
[3]	The San Diego Properties included the following: 4910 Directors Place, 10020 Pacific Mesa Boulevard, 6055 Lusk Avenue, 5010 and 5005 Wateridge Vista Drive, 15435 and 15445 Innovation Drive, and 15051, 15073, 15231, 15253, 15333 and 15378 Avenue of Science.
[4]	We closed on the disposition of this property on October 2, 2013. The sales price was $9.6 million.

Acquisitions_Details

Acquisitions (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013		Sep. 30, 2013		Sep. 30, 2013		Jun. 27, 2013
	building		Office Properties Acquisitions [Member]		320 & 321 Westlake Terry, Seattle WA [Member]		12780 and 12790 El Camino Real, Sandiego, CA [Member]		Redwood City Partners, LLC [Member]
			sqft		building		sqft
			building		sqft		building
Business Acquisition [Line Items]
Date of Acquisition					16-Jan-13	[1],[2]	19-Sep-13	[3]
Number of buildings	14		4		2	[1],[2]	2	[3]
Rentable square feet			539,338		320,398	[1],[2]	218,940	[3]
Occupancy as of September 30, 2013					100.00%	[1],[2]	100.00%	[3]
Purchase price			$296,400,000	[4]	$170,000,000	[1],[2],[4]	$126,400,000	[3],[4]
Assets
Undeveloped land and construction in progress									11,222,000
Land and improvements			53,790,000	[5]
Buildings and improvements			218,211,000	[5],[6]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Undeveloped Land And Construction-in-Progress			9,360,000	[5],[7]
Deferred leasing costs and acquisition-related intangible assets			30,789,000	[5],[8]
Total assets acquired			312,150,000	[5]					11,222,000
Liabilities
Deferred revenue and acquisition-related intangible liabilities			4,190,000	[5],[9]
Secured debt			95,496,000	[10],[5]					1,750,000	[11]
Accounts payable, accrued expenses, and other liabilities			422,000	[5]					1,952,000
Total liabilities assumed			100,108,000	[5]					3,702,000
Noncontrolling interest	55,486,000	46,303,000							4,885,000
Net assets and liabilities acquired			$212,042,000	[12],[5]					$2,635,000
[1]	We acquired these properties through a new special purpose entity wholly owned by the Finance Partnership.
[2]	In connection with this acquisition, we assumed secured debt with an outstanding principal balance of $83.9 million that was recorded at fair value on the acquisition date, resulting in a premium of approximately $11.6 million (see Note 5).
[3]	As of September 30, 2013, these properties, together the “Heights of Del Mar” project, are temporarily being held in a separate VIE to facilitate potential Section 1031 Exchanges (see Note 1). The $126.4 million purchase price includes $9.4 million for 4.2 acres of undeveloped land the Company acquired in connection with this acquisition.
[4]	Excludes acquisition-related costs and includes assumed tenant improvements.
[5]	The purchase price of the two acquisitions completed during the nine months ended September 30, 2013 were individually less than 5% and in aggregate less than 10% of the Company’s total assets as of September 30, 2013.
[6]	Represents buildings, building improvements and tenant improvements.
[7]	In connection with one of the acquisitions, we acquired undeveloped land of approximately 4.2 acres that was added to the Company’s future development pipeline upon acquisition.
[8]	Represents in-place leases (approximately $19.6 million with a weighted average amortization period of 4.7 years), above-market leases (approximately $3.2 million with a weighted average amortization period of 6.1 years), and leasing commissions (approximately $7.9 million with a weighted average amortization period of 5.9 years).
[9]	Represents below-market leases (approximately $4.2 million with a weighted average amortization period of 7.7 years).
[10]	Represents the mortgage loan, which includes an unamortized premium of approximately $11.6 million at the date of acquisition, assumed in connection with the properties acquired in January 2013 (see Note 5).
[11]	This note was repaid as of September 30, 2013.
[12]	Reflects the purchase price net of assumed secured debt and other lease-related obligations.

Acquisitions_Details_Textuals

Acquisitions (Details Textuals) (USD $)

9 Months Ended

9 Months Ended

9 Months Ended

1 Months Ended

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Jun. 27, 2013

Sep. 30, 2013

Sep. 30, 2013

Oct. 29, 2013

building

In-Place Leases [Member]

Above-Market Leases [Member]

Deferred Leasing Costs [Member]

6.05% Mortgage Payable Due June 1, 2019 [Member]

Office Properties Acquisitions [Member]

320 & 321 Westlake Terry, Seattle WA [Member]

12780 and 12790 El Camino Real, Sandiego, CA [Member]

Redwood City Partners, LLC [Member]

Purchase Price Of Business Combination [Member]

Purchase Price Of Business Combination [Member]

Subsequent Event [Member]

sqft

Kilroy Realty, L.P. [Member]

building

building

acre

acre

Assets, Total [Member]

Assets, Total [Member]

acre

Secured Debt [Member]

building

sqft

Office Properties Acquisitions [Member]

320 & 321 Westlake Terry, Seattle WA [Member]

Business Acquisition [Line Items]

Number of buildings

14

4

2

[1],[2]

2

[3]

Concentration risk, percentage

10.00%

5.00%

Principal amount of secured debt

$83,900,000

Debt premium

11,600,000

Deferred leasing costs and acquisition-related intangible assets

19,600,000

3,200,000

7,900,000

30,789,000

[4],[5]

Weighted average amortization period in years for deferred leasing and acquisition-related intangible assets

4 years 8 months 0 days

6 years 1 month 0 days

5 years 11 months 0 days

Below Market Lease, Acquired

4,200,000

Weighted average amortization period in years for acquisition-related liabilities

7 years 8 months 0 days

Area of real estate property

1,159,185

300,000

Payments to acquire land

$9,400,000

$17,000,000

Area of land

4.2

0.35

2

[1]

We acquired these properties through a new special purpose entity wholly owned by the Finance Partnership.

[2]

In connection with this acquisition, we assumed secured debt with an outstanding principal balance of $83.9 million that was recorded at fair value on the acquisition date, resulting in a premium of approximately $11.6 million (see Note 5).

[3]

As of September 30, 2013, these properties, together the “Heights of Del Mar” project, are temporarily being held in a separate VIE to facilitate potential Section 1031 Exchanges (see Note 1). The $126.4 million purchase price includes $9.4 million for 4.2 acres of undeveloped land the Company acquired in connection with this acquisition.

[4]

The purchase price of the two acquisitions completed during the nine months ended September 30, 2013 were individually less than 5% and in aggregate less than 10% of the Company’s total assets as of September 30, 2013.

[5]

Represents in-place leases (approximately $19.6 million with a weighted average amortization period of 4.7 years), above-market leases (approximately $3.2 million with a weighted average amortization period of 6.1 years), and leasing commissions (approximately $7.9 million with a weighted average amortization period of 5.9 years).

Deferred_Leasing_Costs_and_Acq2

Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, net (Details) (USD $)	Sep. 30, 2013		Dec. 31, 2012
In Thousands, unless otherwise specified
Deferred Leasing Costs and Acquisition-related Intangible Assets, Net
Total deferred leasing costs and acquisition-related intangible assets, net	$190,085		$189,968
Acquisition-related Intangible Liabilities, Net
Total acquisitions-related intangible liabilities, net	53,014	[1]	59,129	[1]
Deferred Leasing Costs [Member]
Deferred Leasing Costs and Acquisition-related Intangible Assets, Net
Finite-lived intangible assets, gross	170,609		168,087
Finite-lived intangible assets accumulated amortization	-59,943		-61,443
Finite-lived intangible assets, net	110,666		106,644
Above-Market Leases [Member]
Deferred Leasing Costs and Acquisition-related Intangible Assets, Net
Finite-lived intangible assets, gross	28,842		27,977
Finite-lived intangible assets accumulated amortization	-14,038		-12,180
Finite-lived intangible assets, net	14,804	[2]	15,797
In-Place Leases [Member]
Deferred Leasing Costs and Acquisition-related Intangible Assets, Net
Finite-lived intangible assets, gross	108,612		101,061
Finite-lived intangible assets accumulated amortization	-44,476		-34,019
Finite-lived intangible assets, net	64,136		67,042
Below Market Ground Lease Obligation [Member]
Deferred Leasing Costs and Acquisition-related Intangible Assets, Net
Finite-lived intangible assets, gross	490		690
Finite-lived intangible assets accumulated amortization	-11		-205
Finite-lived intangible assets, net	479	[3]	485
Below Market Lease [Member]
Acquisition-related Intangible Liabilities, Net
FiniteLivedIntangibleLiabilitiesGross	70,966		70,486
Accumulated amortization	-24,074		-17,555
Acquisition-related Intangible Liabilities, net	46,892	[1],[4]	52,931	[1]
Above-Market Ground Lease Obligation [Member]
Acquisition-related Intangible Liabilities, Net
FiniteLivedIntangibleLiabilitiesGross	6,320		6,320
Accumulated amortization	-198		-122
Acquisition-related Intangible Liabilities, net	$6,122	[1],[5]	$6,198	[1]
[1]	Included in deferred revenue and acquisition-related intangible liabilities, net in the consolidated balance sheets.
[2]	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.
[3]	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.
[4]	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.
[5]	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.

Deferred_Leasing_Costs_and_Acq3

Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, net (Details 1) (USD $)	3 Months Ended				9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012		Dec. 31, 2012
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 intangible assets	$12,661		$9,716		$37,343		$24,461
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 intangible assets	6,945	[1]	5,238	[1]	20,882	[1]	14,126	[1]
Estimated annual amortization related to acquisition-related intangibles
Remaining 2013	6,384				6,384
2014	23,533				23,533
2015	19,669				19,669
2016	16,920				16,920
2017	14,468				14,468
Thereafter	29,692				29,692
Finite-lived intangible assets, net	110,666				110,666				106,644
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 intangible assets	1,417	[2]	1,459	[2]	4,214	[2]	4,205	[2]
Estimated annual amortization related to acquisition-related intangibles
Remaining 2013	1,367	[3]			1,367	[3]
2014	4,837	[3]			4,837	[3]
2015	3,035	[3]			3,035	[3]
2016	2,007	[3]			2,007	[3]
2017	1,690	[3]			1,690	[3]
Thereafter	1,868	[3]			1,868	[3]
Finite-lived intangible assets, net	14,804	[3]			14,804	[3]			15,797
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 intangible assets	7,677	[1]	6,479	[1]	22,546	[1]	14,858	[1]
Estimated annual amortization related to acquisition-related intangibles
Remaining 2013	6,549				6,549
2014	19,053				19,053
2015	12,676				12,676
2016	9,445				9,445
2017	7,744				7,744
Thereafter	8,669				8,669
Finite-lived intangible assets, net	64,136				64,136				67,042
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 intangible assets	2	[4]	52	[4]	6	[4]	153	[4]
Estimated annual amortization related to acquisition-related intangibles
Remaining 2013	2	[5]			2	[5]
2014	8	[5]			8	[5]
2015	8	[5]			8	[5]
2016	8	[5]			8	[5]
2017	8	[5]			8	[5]
Thereafter	445	[5]			445	[5]
Finite-lived intangible assets, net	479	[5]			479	[5]			485
Below Market Leases [Member]
Amortization for the period related to deferred leasing costs and acquisition-related intangibles
Amortization for the period related to acquistion-related liabilities	-3,355	[6]	-3,487	[6]	-10,229	[6]	-8,821	[6]
Estimated annual amortization related to acquisition-related intangibles
Remaining 2013	-3,201	[7]			-3,201	[7]
2014	-11,903	[7]			-11,903	[7]
2015	-9,385	[7]			-9,385	[7]
2016	-7,195	[7]			-7,195	[7]
2017	-6,127	[7]			-6,127	[7]
Thereafter	-9,081	[7]			-9,081	[7]
Acquisition-related Intangible Liabilities, net	-46,892	[7],[8]			-46,892	[7],[8]			-52,931	[8]
Above-Market Ground Lease Obligation [Member]
Amortization for the period related to deferred leasing costs and acquisition-related intangibles
Amortization for the period related to acquistion-related liabilities	-25	[9]	-25	[9]	-76	[9]	-60	[9]
Estimated annual amortization related to acquisition-related intangibles
Remaining 2013	-25	[10]			-25	[10]
2014	-101	[10]			-101	[10]
2015	-101	[10]			-101	[10]
2016	-101	[10]			-101	[10]
2017	-101	[10]			-101	[10]
Thereafter	-5,693	[10]			-5,693	[10]
Acquisition-related Intangible Liabilities, net	($6,122)	[10],[8]			($6,122)	[10],[8]			($6,198)	[8]
[1]	The amortization of deferred leasing costs and in-place leases is recorded to depreciation and amortization expense 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]	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.
[4]	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.
[5]	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.
[6]	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.
[7]	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.
[8]	Included in deferred revenue and acquisition-related intangible liabilities, net in the consolidated balance sheets.
[9]	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.
[10]	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_Details

Receivables (Details) (USD $)	Sep. 30, 2013		Dec. 31, 2012
In Thousands, unless otherwise specified
Current Receivables, net
Current receivables	$14,301		$11,801
Allowance for uncollectible tenant receivables	-2,532		-2,581
Current receivables, net	11,769	[1]	9,220
Deferred Rent Receivables, net
Deferred rent receivables	123,632		118,025
Allowance for deferred rent receivables	-1,973		-2,607
Deferred rent receivables, net	$121,659	[2]	$115,418
[1]	Excludes current receivables, net related to properties held for sale at September 30, 2013.
[2]	Excludes deferred rent receivables, net related to properties held for sale at September 30, 2013.

Secured_and_Unsecured_Debt_of_2

Secured and Unsecured Debt of the Operating Partnership (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013		Sep. 30, 2013		Dec. 31, 2012
Debt Instrument [Line Items]
Secured Debt	$563,898,000	[1]	$563,898,000	[1]	$561,096,000	[1]
Kilroy Realty, L.P. [Member]
Debt Instrument [Line Items]
Secured Debt	563,898,000		563,898,000		561,096,000
Kilroy Realty, L.P. [Member] | Secured Debt [Member] | 4.27% Mortgage Payable due Feb. 01, 2018 [Member]
Debt Instrument [Line Items]
Annual Stated Interest Rate	4.27%	[2]	4.27%	[2]
GAAP Effective Rate	4.27%	[2],[3]	4.27%	[2],[3]
Maturity Date			1-Feb-18
Secured Debt	133,689,000	[1]	133,689,000	[1]	135,000,000	[1]
Kilroy Realty, L.P. [Member] | Secured Debt [Member] | 4.48% Mortgage Payable due July 1, 2027 [Member]
Debt Instrument [Line Items]
Annual Stated Interest Rate	4.48%	[2]	4.48%	[2]
GAAP Effective Rate	4.48%	[2],[3]	4.48%	[2],[3]
Maturity Date			1-Jul-27
Secured Debt	97,000,000	[1],[4]	97,000,000	[1],[4]	97,000,000	[1],[4]
Kilroy Realty, L.P. [Member] | Secured Debt [Member] | 6.05% Mortgage Payable Due June 1, 2019 [Member]
Debt Instrument [Line Items]
Annual Stated Interest Rate	6.05%	[2]	6.05%	[2]
GAAP Effective Rate	3.50%	[2],[3]	3.50%	[2],[3]
Maturity Date			1-Jun-19
Secured Debt	93,306,000	[1],[4],[5]	93,306,000	[1],[4],[5]	0	[1],[4],[5]
Principal amount of secured debt	83,900,000		83,900,000
Debt premium	11,600,000		11,600,000
Amortization period of debt	6 years 5 months
Kilroy Realty, L.P. [Member] | Secured Debt [Member] | 6.37% Mortgage Payable due April 01, 2013 [Member]
Debt Instrument [Line Items]
Annual Stated Interest Rate	6.37%	[2]	6.37%	[2]
GAAP Effective Rate	3.55%	[2],[3]	3.55%	[2],[3]
Maturity Date			1-Apr-13
Secured Debt	0	[1],[6]	0	[1],[6]	83,116,000	[1],[6]
Kilroy Realty, L.P. [Member] | Secured Debt [Member] | 6.51% Mortgage Payable due Feb. 01, 2017 [Member]
Debt Instrument [Line Items]
Annual Stated Interest Rate	6.51%	[2]	6.51%	[2]
GAAP Effective Rate	6.51%	[2],[3]	6.51%	[2],[3]
Maturity Date			1-Feb-17
Secured Debt	67,907,000	[1]	67,907,000	[1]	68,615,000	[1]
Kilroy Realty, L.P. [Member] | Secured Debt [Member] | 5.23% Mortgage Payable due Jan. 01, 2016 [Member]
Debt Instrument [Line Items]
Annual Stated Interest Rate	5.23%	[2]	5.23%	[2]
GAAP Effective Rate	3.50%	[2],[3]	3.50%	[2],[3]
Maturity Date			1-Jan-16
Secured Debt	55,007,000	[1],[4]	55,007,000	[1],[4]	56,302,000	[1],[4]
Kilroy Realty, L.P. [Member] | Secured Debt [Member] | 5.57% Morgage Payable Due Feb. 11, 2016 [Member]
Debt Instrument [Line Items]
Annual Stated Interest Rate	5.57%	[2]	5.57%	[2]
GAAP Effective Rate	3.25%	[2],[3]	3.25%	[2],[3]
Maturity Date			11-Feb-16
Secured Debt	41,999,000	[1],[4]	41,999,000	[1],[4]	43,016,000	[1],[4]
Kilroy Realty, L.P. [Member] | Secured Debt [Member] | 5.09% Mortgage Payable due Aug. 7, 2015 [Member]
Debt Instrument [Line Items]
Annual Stated Interest Rate	5.09%	[2]	5.09%	[2]
GAAP Effective Rate	3.50%	[2],[3]	3.50%	[2],[3]
Maturity Date			7-Aug-15
Secured Debt	34,979,000	[1],[4]	34,979,000	[1],[4]	35,379,000	[1],[4]
Kilroy Realty, L.P. [Member] | Secured Debt [Member] | 4.94% Mortgage Payable due April 15, 2015 [Member]
Debt Instrument [Line Items]
Annual Stated Interest Rate	4.94%	[2]	4.94%	[2]
GAAP Effective Rate	4.00%	[2],[3]	4.00%	[2],[3]
Maturity Date			15-Apr-15
Secured Debt	27,970,000	[1],[4]	27,970,000	[1],[4]	28,941,000	[1],[4]
Kilroy Realty, L.P. [Member] | Secured Debt [Member] | 7.15% Mortgage Payable due May 01, 2017 [Member]
Debt Instrument [Line Items]
Annual Stated Interest Rate	7.15%	[2]	7.15%	[2]
GAAP Effective Rate	7.15%	[2],[3]	7.15%	[2],[3]
Maturity Date			1-May-17
Secured Debt	9,546,000	[1]	9,546,000	[1]	11,210,000	[1]
Kilroy Realty, L.P. [Member] | Secured Debt [Member] | Municipal Bonds [Member]
Debt Instrument [Line Items]
Secured Debt	$2,495,000	[1]	$2,495,000	[1]	$2,517,000	[1]
[1]	Amounts reported include the amounts of unamortized debt premiums and discounts for the periods presented.
[2]	All interest rates presented are fixed-rate interest rates.
[3]	This represents the rate at which interest expense is recorded for financial reporting purposes, which reflects the amortization of discounts/premiums, excluding debt issuance costs.
[4]	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.
[5]	In January 2013, in connection with the acquisition of two office buildings in Seattle, Washington, we assumed a mortgage loan that is secured by the project. The assumed mortgage had a principal balance of $83.9 million at the acquisition date and was recorded at fair value on the date of the acquisition resulting in a premium of approximately $11.6 million. The loan requires monthly principal and interest payments based on a 6.4 year amortization period.
[6]	In January 2013, we repaid this loan prior to the stated maturity date.

Secured_and_Unsecured_Debt_of_3

Secured and Unsecured Debt of the Operating Partnership (Details 1) (USD $)	3 Months Ended			9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012	Sep. 30, 2013		Sep. 30, 2012		Dec. 31, 2012
Debt Instrument [Line Items]
Unsecured debt	$1,431,048,000			$1,431,048,000				$1,130,895,000
Balance and significant terms of the Exchangeable Notes outstanding
Net carrying amount of liability component	167,236,000			167,236,000				163,944,000
Per Share Average Trading Price Of Companys Common Stock On Stock Exchange Abstract
Average trading price of the Companys stock	$51.57		$47.56	$52.42		$45.74
Kilroy Realty, L.P. [Member]
Debt Instrument [Line Items]
Unsecured debt	1,431,048,000			1,431,048,000				1,130,895,000
Balance and significant terms of the Exchangeable Notes outstanding
Net carrying amount of liability component	167,236,000			167,236,000				163,944,000
Kilroy Realty, L.P. [Member] | Secured Debt [Member] | 6.05% Mortgage Payable Due June 1, 2019 [Member]
Balance and significant terms of the Exchangeable Notes outstanding
Maturity Date				1-Jun-19
Stated coupon rate	6.05%	[1]		6.05%	[1]
Effective interest rate	3.50%	[1],[2]		3.50%	[1],[2]
Kilroy Realty, L.P. [Member] | Exchangeable Notes [Member]
Interest Expense for the Exchangeable Notes
Contractual interest payments	1,833,000		1,833,000	5,498,000		6,888,000	[3]
Amortization of discount	1,116,000		1,041,000	3,291,000		3,993,000	[3]
Interest expense attributable to the Exchangeable Notes	2,949,000		2,874,000	8,789,000		10,881,000	[3]
Kilroy Realty, L.P. [Member] | Exchangeable Notes [Member] | 4.25% Exchangeable Notes [Member]
Balance and significant terms of the Exchangeable Notes outstanding
Principal amount	172,500,000		172,500,000	172,500,000		172,500,000		172,500,000
Unamortized discount	-5,264,000			-5,264,000				-8,556,000
Net carrying amount of liability component	167,236,000			167,236,000				163,944,000
Carrying amount of equity component	19,835,000			19,835,000
Stated coupon rate	4.25%	[4]		4.25%	[4]
Effective interest rate	7.13%	[5]		7.13%	[5]
Exchange rate per $1,000 principal value of the Exchangeable Notes, as adjusted	27.8307	[6]
Exchange price, as adjusted	$35.93	[6]
Number of Shares on which aggregate consideration to be delivered upon conversion is determined	4,800,796	[6]
Minimum percentage of exchange price	130.00%
Per Share Average Trading Price Of Companys Common Stock On Stock Exchange Abstract
Fair Value Of Shares Upon Conversion If Exchangeable Notes Were Converted On Specified Date	245,200,000		225,100,000	248,000,000		218,600,000
Debt Instrument, Convertible, If-converted Value in Excess of Principal	72,700,000		52,600,000	75,500,000		46,100,000
Capped call transactions
Referenced shares of common stock	4,800,796			4,800,796
Exchange price including effect of capped calls	$42.81			$42.81
[1]	All interest rates presented are fixed-rate interest rates.
[2]	This represents the rate at which interest expense is recorded for financial reporting purposes, which reflects the amortization of discounts/premiums, excluding debt issuance costs.
[3]	The Company repaid the 3.25% Exchangeable Notes in April 2012. Interest payments and discount amortization for the three and nine months ended September 30, 2013 and three months ended September 30, 2012 are solely attributable to the 4.25% Exchangeable Notes.
[4]	Interest on the 4.25% Exchangeable Notes is payable semi-annually in arrears on May 15th and November 15th of each year.
[5]	The rate at which we record interest expense for financial reporting purposes, which reflects the amortization of the discounts on the 4.25% Exchangeable Notes. This rate represents our conventional debt borrowing rate at the date of issuance.
[6]	The exchange rate, exchange price, and the number of shares to be delivered upon conversion are subject to adjustment under certain circumstances including increases in our common dividends.

Unsecured_Senior_Notes_Details

Unsecured Senior Notes (Details 2) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013
In Thousands, unless otherwise specified			Kilroy Realty, L.P. [Member]	Kilroy Realty, L.P. [Member]	Kilroy Realty, L.P. [Member]
					Unsecured Senior Notes, 3.8%, Due 2023 [Member]
					Senior Notes [Member]
Debt Instrument [Line Items]
Unsecured debt	$1,431,048	$1,130,895	$1,431,048	$1,130,895	$300,000
Maturity Date					15-Jan-23
Stated coupon rate					3.80%
Debt Instrument, Unamortized Discount					$100

Unsecured_Revolving_Credit_Fac

Unsecured Revolving Credit Facility (Details 3) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013		Sep. 30, 2013		Dec. 31, 2012		Dec. 31, 2012
			Kilroy Realty, L.P. [Member]	Kilroy Realty, L.P. [Member]	Kilroy Realty, L.P. [Member]		Kilroy Realty, L.P. [Member]		Kilroy Realty, L.P. [Member]		Kilroy Realty, L.P. [Member]
					Revolving Credit Facility [Member]		Revolving Credit Facility [Member]		Revolving Credit Facility [Member]		Line of Credit [Member]
Line of Credit Facility [Line Items]
Unsecured debt additional borrowing amount					$200,000,000
Terms of the Credit Facility
Unsecured line of credit	0	185,000,000	0	185,000,000	0		0		185,000,000
Remaining borrowing capacity					500,000,000		500,000,000		315,000,000
Total borrowing capacity					500,000,000	[1]	500,000,000	[1]	500,000,000	[1]
Interest rate									1.66%	[2]
Facility fee - annual rate					0.30%	[3]
Maturity date					3-Apr-17	[4]
Debt Instrument, Basis Spread on Variable Rate							1.45%
Debt Issuance Cost											$10,200,000
[1]	We may elect to borrow, subject to bank approval, up to an additional $200.0 million under an accordion feature under the terms of the revolving credit facility.
[2]	The revolving credit facility interest rate was calculated based on an annual rate of LIBOR plus 1.450% as of both September 30, 2013 and December 31, 2012. No interest rate is shown as of September 30, 2013 because no borrowings were outstanding.
[3]	The facility fee is paid on a quarterly basis and is calculated based on the total borrowing capacity. In addition to the facility fee, from 2010 to 2012 we incurred debt origination and legal costs totaling approximately $10.2 million that are currently being amortized through the maturity date of the revolving credit facility.
[4]	Under the terms of the revolving credit facility, we may exercise an option to extend the maturity date by one year.

Debt_Maturities_Details_4

Debt Maturities (Details 4) (Debt [Member], Kilroy Realty, L.P. [Member], USD $)	Sep. 30, 2013
Debt [Member] | Kilroy Realty, L.P. [Member]
Stated debt maturities and scheduled amortization payments, excluding debt discounts
Remaining 2013	$2,387,000
2014	265,346,000
2015	395,104,000
2016	249,431,000
2017	71,748,000
Thereafter	1,169,742,000
Total	2,153,758,000	[1]
Unamortized discount (premium)	($8,400,000)
[1]	Includes gross principal balance of outstanding debt before impact of net unamortized premiums totaling approximately $8.4 million.

Secured_and_Unsecured_Debt_of_4

Secured and Unsecured Debt of the Operating Partnership Capitalized Interest and Loan Fees (Details 5) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Capitalized Interest and Loan Fees [Line Items]
Interest Expense	$18,853	$19,854	$58,021	$60,172
Kilroy Realty, L.P. [Member]
Capitalized Interest and Loan Fees [Line Items]
Gross interest expense	27,942	24,843	83,322	73,326
Capitalized interest	-9,089	-4,989	-25,301	-13,154
Interest Expense	$18,853	$19,854	$58,021	$60,172

Noncontrolling_Interests_on_th1

Noncontrolling Interests on the Company's Consolidated Financial Statements (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Noncontrolling Interest [Abstract]
Percentage of general partnership interest owned by the company in the Operating Partnership	97.80%	97.60%	97.60%
Percentage of Common limited partnership interest owned by certain non-affiliated investors and certain directors and officers of the Company in the Operating Partnership	2.20%	2.40%	2.40%
Common units outstanding held by common limited partners	1,821,503	1,826,503	1,826,503
Common stock, par value	$0.01
Aggregate value upon redemption of outstanding noncontrolling common units	$92,300,000	$85,400,000
Noncontrolling Interest in consolidated subsidiary (Notes 2 and 6)	$4,885,000	$0

Stockholders_Equity_of_the_Com2

Stockholders' Equity of the Company (Details) (USD $)	9 Months Ended				0 Months Ended		3 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Dec. 31, 2012	Sep. 18, 2013	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013
			Common Stock [Member]	Common Stock [Member]	Issuance of Equity - equity offering [Domain]	Issuance of Equity - at the market ofering [Member]	Issuance of Equity - at the market ofering [Member]	Issuance of Equity - at the market ofering [Member]
					Common Stock [Member]		Common Stock [Member]	Common Stock [Member]
Common Stock of the Company [Abstract]
Issuance of common stock, shares					6,175,000		226,430	1,040,838
Proceeds from Issuance of Common stock, net					$295,900,000		$11,400,000	$54,400,000
At the Market Stock Offering Program Aggregate Value Of Common Stock								200,000,000
Average price per common shares sold							$51.12	$53.11
Net proceeds from issuance of common stock (Note 7)	349,951,000	662,371,000					11,600,000	55,300,000
Common stock, shares issued			82,113,491	74,926,981		2,183,261
At Market Stock Aggregate Gross Sales Price of Common Stock							105,300,000	105,300,000
At the Market Stock Offering Program Remained Available For Issuance								$94,700,000

Partners_Capital_of_the_Operat2

Partners' Capital of the Operating Partnership (Details) (USD $)

9 Months Ended

0 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

Sep. 30, 2013

Sep. 30, 2012

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2012

Sep. 18, 2013

Sep. 18, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Kilroy Realty, L.P. [Member]

Kilroy Realty, L.P. [Member]

Kilroy Realty, L.P. [Member]

Issuance of Equity - equity offering [Domain]

Capital Units [Member]

Issuance of Equity - at the market ofering [Member]

Issuance of Equity - at the market ofering [Member]

Issuance of Equity - at the market ofering [Member]

Issuance of Equity - at the market ofering [Member]

Capital Units [Member]

Capital Units [Member]

Capital Units [Member]

Common Stock [Member]

Common Stock [Member]

Common Stock [Member]

Capital Units [Member]

Capital Units [Member]

General Partners' Capital Account [Abstract]

Issuance of common stock, shares

6,175,000

226,430

1,040,838

Proceeds from Issuance of Common stock, net

$295,900,000

$11,400,000

$54,400,000

Net proceeds from issuance of common stock

$349,951,000

$662,371,000

$11,600,000

$55,300,000

Partners' Capital Account, Units, Sold in Public Offering

6,175,000

226,430

1,040,838

General Partners' Capital Account, Units Outstanding

82,113,491

74,926,981

74,692,939

Noncontrolling Interest, Ownership Percentage by Parent

97.80%

97.60%

97.60%

Common units held by limited partners

1,821,503

1,826,503

1,826,503

Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners

2.20%

2.40%

2.40%

ShareBased_Compensation_Market

Share-Based Compensation Market Measure-based RSU Grant (Details) (Market Measure-Based Restricted Stock Units (RSUs) [Member], USD $)	9 Months Ended	0 Months Ended	9 Months Ended						9 Months Ended			9 Months Ended
	Sep. 30, 2012	Mar. 30, 2012	Sep. 30, 2013	Sep. 30, 2013		Sep. 30, 2013		Dec. 31, 2012	Sep. 30, 2013		Dec. 31, 2012	Sep. 30, 2013
		Chief Executive Officer [Member]	Chief Executive Officer [Member]	Weighted Average Grant Date Fair Value Per Share [Member]		Vested Restricted Stock Units R S U [Member]		Vested Restricted Stock Units R S U [Member]	Restricted Stock Units (RSUs) [Member]		Restricted Stock Units (RSUs) [Member]	Nonvested Restricted Stock Units R S U [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, Number						14,748		14,748
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number									174,108		103,239
Expected Volatility Rate			27.00%
Risk Free Interest Rate			0.90%
Expected Dividend Rate			3.60%
Expected Term			6 years
Outstanding, Jan. 01, 2013												88,491
Granted	103,239	103,239				0			9,542			9,542
Vested	0					0			0			0
Settled						0			0			0
Issuance of dividend equivalents						0			0			0
Modified from time based						0	[1]		61,327	[1]		61,327	[1]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period						0			0
Outstanding, Sept. 30, 2013												159,360
Oustanding, Jan. 01, 2013				$41.20
Granted	$41.20		$44.55	$44.55
Vested	$0			$0
Modified from time based				$53.05	[1]
Oustanding, Sept. 30, 2013				$45.96
[1]	On April 4, 2013 the terms of time-based RSU’s granted to certain officers of the Company in January were modified to include market-measure and performance-based vesting requirements.

ShareBased_Compensation_Timeba

Share-Based Compensation Time-based RSUs (Details) (Time-Based Restricted Stock Units (RSUs) [Member], USD $)

9 Months Ended

In Thousands, except Share data, unless otherwise specified

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Dec. 31, 2012

Nonvested Shares [Member]

Nonvested Shares [Member]

Vested Restricted Stock Units R S U [Member]

Vested Restricted Stock Units R S U [Member]

Restricted Stock Units (RSUs) [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, Non-Option Equity Instruments, Outstanding, Number

1,167,573

1,048,863

Share Based Compensation Arrangement By Share Based Payment Award, Equity Instruments Other Than Options, Vested, Number

849,614

769,761

Outstanding, Jan. 01, 2013

279,102

Granted

173,758

204,829

0

173,758

Vested

-73,574

-73,574

-58,940

0

Settled

-10,342

[1]

-10,342

[1]

Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Issuance Of Dividend Equivalents In Period

20,421

[2]

20,421

[2]

Modified to time based

-61,327

[3]

0

[3]

61,327

[3]

Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period

3,800

[1],[4]

3,800

[1],[4]

Outstanding, Sept. 30, 2013

317,959

Oustanding, Jan. 01, 2013

$41.30

Granted

$49.45

$44.34

Vested

$38.80

Modified to time based

$53.05

[3]

Oustanding, Sept. 30, 2013

$46.13

Total Fair Value

$3,677

[5]

$2,420

[5]

[1]

Represents vested RSUs that are settled in cash or shares of the Company’s common stock.

[2]

RSUs issued as dividend equivalents are vested upon issuance.

[3]

During the second quarter the terms of time-based RSUs granted to certain officers of the Company in January were modified to include market-measure based vesting requirements.

[4]

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 issuance, vesting or settlement of RSUs in accordance with the terms of the 2006 Plan.

[5]

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.

ShareBased_Compensation_Nonves

Share-Based Compensation Nonvested Shares (Details) (Restricted Stock [Member], USD $)	3 Months Ended	9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2013		Sep. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted				62,137
Vested				-35,623
Granted				$41.84
Shares Paid for Tax Withholding for Share Based Compensation	20,880
Total Fair Value		$2,290	[1]	$1	[1]
Nonvested Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding, Jan. 01, 2013		95,241
Granted		0
Vested		-47,291	[2]
Outstanding, Sept. 30, 2013	47,950	47,950
Weighted Average Grant Date Fair Value Per Share [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Oustanding, Jan. 01, 2013		$40.42
Granted		$0
Vested		$39.12
Oustanding, Sept. 30, 2013	41.71	$41.71
[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.
[2]	The total shares vested include 20,880 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 obligations.

ShareBased_Compensation_Stock_

Share-Based Compensation Stock Options (Details) (USD $)	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Dec. 31, 2012
In Millions, except Share data, unless otherwise specified			Stock Options [Member]	Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding, Jan. 01, 2013	1,525,000	1,540,000	1,540,000
Granted			0
Exercise			-3,000
Forfeited			-12,000
Outstanding, Sept. 30, 2013	1,525,000	1,540,000	1,525,000
Outstanding, Jan. 01, 2013			$42.61	$42.61
Granted			$0
Exercise			$42.61
Forfeited			$42.61
Outstanding, Sept. 30, 2013			$42.61	$42.61
Weighted Average Remaining Contractual Term (years)			8 years 5 months
Options Exercisable			305,000
Intrinsic Value			$11.20

ShareBased_Compensation_Detail

Share-Based Compensation (Details Textuals) (USD $)

3 Months Ended

9 Months Ended

9 Months Ended

0 Months Ended

9 Months Ended

In Millions, except Share data, unless otherwise specified

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Apr. 04, 2013

Apr. 04, 2013

Apr. 04, 2013

Mar. 30, 2012

Sep. 30, 2013

Full Value Awards [Member]

Restricted Stock [Member]

Time-Based Restricted Stock Units (RSUs) [Member]

Market Measure-Based Restricted Stock Units (RSUs) [Member]

Chief Executive Officer [Member]

Chief Executive Officer [Member]

Chief Executive Officer [Member]

Chief Executive Officer [Member]

Chief Executive Officer [Member]

Restricted Stock [Member]

Time-Based Restricted Stock Units (RSUs) [Member]

Market Measure-Based Restricted Stock Units (RSUs) [Member]

Market Measure-Based Restricted Stock Units (RSUs) [Member]

Market Measure-Based Restricted Stock Units (RSUs) [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Modified to time based

$53.05

[1]

Expected Term

6 years

Share-based Compensation, Historical volatility period

12 years

Share-based Compensation, Grants in Period

62,137

103,239

19,084

103,239

Share-based Compensation, Grant Date Fair Value

$0.50

$0.40

Share-based Compensation, Fair Value Assumptions, Exercise Price

$53.05

Share-based Compensation, Number of Shares Available for Grant

28,355

28,355

9,711

Document Period End Date

30-Sep-13

Share-based Compensation, Vesting, Number of Annual Installments

7 years

Share-Based Compensation (Textuals) [Abstract]

Allocated Share-based Compensation Expense

2.5

2.4

7.2

6.2

Share-based Compensation Capitalized

0.2

0.2

0.6

0.7

Share-based Compensation, Unrecognized costs

$27.90

$27.90

Share-based Compensation, Unrecognized costs, weighted-average vesting period

2 years 4 months

[1]

During the second quarter the terms of time-based RSUs granted to certain officers of the Company in January were modified to include market-measure based vesting requirements.

Commitments_and_Contingencies_

Commitments and Contingencies (Details 1) (USD $)	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013
In Millions, unless otherwise specified		Maximum [Member]	Former Tenant Litigation Case [Member]	Property Damage Litigation Case [Member]
Long-term Purchase Commitment [Line Items]
Commitments for contracts and executed leases, operating and redevelopment and development properties	$447.70
Purchase Option, Maximum Price		27.5
Proceeds from Legal Settlements			$3.70	$5.20

Fair_Value_Measurements_and_Di2

Fair Value Measurements and Disclosures (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Fair value adjustment of marketable securities and deferred compensation plan liability
Net gain (loss) on marketable securities	$669	$315	$995	$595

Fair_Value_Measurements_and_Di3

Fair Value Measurements and Disclosures (Details 1) (USD $)	Sep. 30, 2013		Dec. 31, 2012
Liabilities
Secured Debt	$563,898,000	[1]	$561,096,000	[1]
Exchangeable senior notes, net	167,236,000		163,944,000
Unsecured debt	1,431,048,000		1,130,895,000
Unsecured line of credit	0		185,000,000
Carrying Value [Member]
Liabilities
Secured Debt	563,898,000		561,096,000
Exchangeable senior notes, net	167,236,000		163,944,000
Unsecured debt	1,431,048,000		1,130,895,000
Unsecured line of credit	0		185,000,000
Fair Value [Member]
Liabilities
Secured Debt	574,661,000	[2]	591,993,000	[2]
Exchangeable senior notes, net	178,379,000	[2]	181,223,000	[2]
Unsecured debt	1,522,228,000	[3]	1,254,047,000	[3]
Unsecured line of credit	0	[2]	185,049,000	[2]
Fair Value (Level 2) [Member] | Carrying Value [Member]
Liabilities
Unsecured debt	589,200,000		557,600,000
Fair Value (Level 2) [Member] | Fair Value [Member]
Liabilities
Unsecured debt	590,000,000		601,000,000
Unsecured Debt [Member] | Fair Value (Level 1) [Member] | Carrying Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Fair Value Disclosure	841,900,000		573,300,000
Unsecured Debt [Member] | Fair Value (Level 1) [Member] | Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument, Fair Value Disclosure	$932,200,000		$653,000,000
[1]	Amounts reported include the amounts of unamortized debt premiums and discounts for the periods presented.
[2]	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.
[3]	Fair value calculated using Level I and Level II inputs. Level I inputs are based on quoted prices for identical instruments in active markets. The carrying value and fair value of the Level I instruments was $841.9 million and $932.2 million, respectively, as of September 30, 2013. The carrying value and fair value of the Level I instruments at December 31, 2012, was $573.3 million and $653.0 million, respectively. The carrying value and fair value of the Level II instruments was $589.2 million and $590.0 million, respectively, as of September 30, 2013. The carrying value and fair value of the Level II instruments at December 31, 2012, was $557.6 million and $601.0 million, respectively.

Discontinued_Operations_Detail

Discontinued Operations (Details) (USD $)	3 Months Ended		9 Months Ended			9 Months Ended					0 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Sep. 30, 2013	Sep. 30, 2013		Sep. 30, 2013		Oct. 02, 2013	Sep. 30, 2013		Sep. 30, 2013		Sep. 30, 2013
	building		building			Agoura Road, 26541, Calabasas, CA [Member]	San Diego Properties, San Diego, CA [Member]		Kaiser Boulevard, Anaheim, California [Member]		Subsequent Event [Member]	Other Segments [Member]		Other Segments [Member]		Other Segments [Member]
	sqft		sqft			sqft	sqft		sqft		Kaiser Boulevard, Anaheim, California [Member]	Properties Held for Sale [Member]		San Diego, California [Member]		Anaheim, California [Member]
						building						building		Properties Held for Sale [Member]		Properties Held for Sale [Member]
														building		building
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of buildings	14		14			1						14	[1]	13	[2],[3]	1	[2],[4]
Rentable Square Feet	1,159,185		1,159,185			90,156	1,099,395	[3]	59,790	[4]
Dispositions Sales Price						$14,700,000					$9,600,000
Disposal Group, Including Discontinued Operation, Balance Sheet Disclosures [Abstract]
Land and improvements	54,273,000		54,273,000
Buildings and improvements	236,792,000		236,792,000
Undeveloped land and construction in progress	1,441,000		1,441,000
Total real estate held for sale	292,506,000		292,506,000
Accumulated depreciation	-70,084,000		-70,084,000
Total real estate held for sale, net	222,422,000		222,422,000
Current receivables, net	303,000		303,000
Deferred rent receivables, net	9,062,000		9,062,000
Deferred leasing costs and acquisition-related intangible assets, net	6,643,000		6,643,000
Prepaid expenses and other assets, net	981,000		981,000
Real estate and other assets held for sale, net	239,411,000		239,411,000		0
Accounts payable and other liabilities	2,554,000		2,554,000
Deferred revenue and acquisition-related intangible liabilities, net	12,785,000		12,785,000
Rents received in advance and tenant security deposits	1,412,000		1,412,000
Liabilities and deferred revenue of real estate assets held for sale	16,751,000		16,751,000		0
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Rental income	6,604,000	10,522,000	18,334,000	33,105,000
Tenant reimbursements	892,000	1,639,000	2,331,000	5,296,000
Other property income	4,610,000	229,000	4,617,000	884,000
Total revenues	12,106,000	12,390,000	25,282,000	39,285,000
Property expenses	2,020,000	2,044,000	3,920,000	6,287,000
Real estate taxes	684,000	1,301,000	2,048,000	3,719,000
Provision for bad debts	-23,000	-194,000	-23,000	-194,000
Depreciation and amortization	3,081,000	4,550,000	8,531,000	13,870,000
Total expenses	5,762,000	7,701,000	14,476,000	23,682,000
Income from discontinued operations before net gain on dispositions of discontinued operations	6,344,000	4,689,000	10,806,000	15,603,000
Net gain on dispositions of discontinued operations	0	0	423,000	72,809,000
Total income from discontinued operations	$6,344,000	$4,689,000	$11,229,000	$88,412,000
[1]	Includes 13 properties located in San Diego, California and one property in Anaheim, California (see Note 12).
[2]	Estimated rentable square feet upon completion.
[3]	The San Diego Properties included the following: 4910 Directors Place, 10020 Pacific Mesa Boulevard, 6055 Lusk Avenue, 5010 and 5005 Wateridge Vista Drive, 15435 and 15445 Innovation Drive, and 15051, 15073, 15231, 15253, 15333 and 15378 Avenue of Science.
[4]	We closed on the disposition of this property on October 2, 2013. The sales price was $9.6 million.

Net_Loss_Income_Available_to_C4

Net (Loss) Income Available to Common Stockholders Per Share of the Company (Details) (USD $)	3 Months Ended				9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Numerator:
Income (loss) from continuing operations	$2,683		($2,167)		$10,289		($4,941)
Loss (income) from continuing operations attributable to noncontrolling common units of the Operating Partnership	14		179		-8		564
Preferred distributions and dividends	-3,312		-5,342		-9,938		-17,775
Allocation to participating securities	-450	[1]	-408	[1]	-1,292	[1]	-1,225	[1]
Numerator for basic and diluted loss from continuing operations available to common stockholders	-1,065		-7,738		-949		-23,377
Income from discontinued operations	6,344		4,689		11,229		88,412
Income from discontinued operations attributable to noncontrolling common units of the Operating Partnership	-145		-112		-258		-2,272
Numerator for basic and diluted net income (loss) available to common stockholders	5,134		-3,161		10,022		62,763
Denominator:
Weighted average common shares outstanding - basic (Note 13)	76,768,893		71,889,475		75,750,822		67,975,309
Effect of dilutive securities - contingently issuable shares and stock options	0		0		0		0
Weighted average common shares outstanding-diluted	76,768,893		71,889,475		75,750,822		67,975,309
Basic earnings per share:
Loss from continuing operations available to common unitholders per common unit-basic (Note 14)	($0.01)		($0.10)		($0.01)		($0.34)
Income from discontinued operations per common share	$0.08		$0.06		$0.14		$1.26
Net (loss) income available to common stockholders per share-basic	$0.07		($0.04)		$0.13		$0.92
Diluted earnings per share:
Loss from continuing operations available to common unitholders per common unit-diluted (Note 14)	($0.01)		($0.10)		($0.01)		($0.34)
Income from discontinued operations per common share	$0.08		$0.06		$0.14		$1.26
Net (loss) income available to common stockholders per share-diluted	$0.07		($0.04)		$0.13		$0.92
Stock options outstanding	1,525,000		1,540,000		1,525,000		1,540,000
Kilroy Realty, L.P. [Member]
Numerator:
Income (loss) from continuing operations	2,683		-2,167		10,289		-4,941
Preferred distributions and dividends	-3,312		-5,342		-9,938		-17,775
Allocation to participating securities	450	[1]	408	[1]	1,292	[1]	1,225	[1]
Numerator for basic and diluted loss from continuing operations available to common stockholders	-1,126		-7,965		-1,119		-24,085
Income from discontinued operations	6,344		4,689		11,229		88,412
Numerator for basic and diluted net income (loss) available to common stockholders	$5,218		($3,276)		$10,110		$64,327
Denominator:
Weighted average common shares outstanding - basic (Note 13)	78,590,396		73,680,259		77,574,907		69,717,834
Effect of dilutive securities - contingently issuable shares and stock options	0		0		0		0
Weighted average common shares outstanding-diluted	78,590,396		73,680,259		77,574,907		69,717,834
Basic earnings per share:
Loss from continuing operations available to common unitholders per common unit-basic (Note 14)	($0.01)		($0.10)		($0.01)		($0.34)
Income from discontinued operations per common share	$0.08		$0.06		$0.14		$1.26
Net (loss) income available to common stockholders per share-basic	$0.07		($0.04)		$0.13		$0.92
Diluted earnings per share:
Loss from continuing operations available to common unitholders per common unit-diluted (Note 14)	($0.01)		($0.10)		($0.01)		($0.34)
Income from discontinued operations per common share	$0.08		$0.06		$0.14		$1.26
Net (loss) income available to common stockholders per share-diluted	$0.07		($0.04)		$0.13		$0.92
[1]	Participating securities include nonvested shares, time-based RSUs and vested market-measure RSUs.

Net_Income_Available_to_Common

Net Income Available to Common Unitholders Per Unit of the Operating Partnership (Details) (USD $)	3 Months Ended				9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Numerator:
Income (loss) from continuing operations	$2,683		($2,167)		$10,289		($4,941)
Total preferred distributions	-3,312		-5,342		-9,938		-17,775
Allocation to participating securities	-450	[1]	-408	[1]	-1,292	[1]	-1,225	[1]
Numerator for basic and diluted loss from continuing operations available to common unitholders	-1,065		-7,738		-949		-23,377
Income from discontinued operations	6,344		4,689		11,229		88,412
Numerator for basic and diluted net income (loss) available to common unitholders	5,134		-3,161		10,022		62,763
Denominator:
Weighted average common units outstanding - basic (Note 14)	76,768,893		71,889,475		75,750,822		67,975,309
Effect of dilutive securities - contingently issuable shares and stock options	0		0		0		0
Weighted average common units outstanding - diluted (Note 14)	76,768,893		71,889,475		75,750,822		67,975,309
Basic earnings per unit:
Loss from continuing operations available to common unitholders per common unit-basic (Note 14)	($0.01)		($0.10)		($0.01)		($0.34)
Income from discontinued operations per common unit	$0.08		$0.06		$0.14		$1.26
Net income (loss) available to common unitholders per unit-basic (Note 14)	$0.07		($0.04)		$0.13		$0.92
Diluted earnings per unit:
Loss from continuing operations available to common unitholders per common unit-diluted (Note 14)	($0.01)		($0.10)		($0.01)		($0.34)
Income from discontinued operations per common unit	$0.08		$0.06		$0.14		$1.26
Net income (loss) available to common unitholders per unit-diluted (Note 14)	$0.07		($0.04)		$0.13		$0.92
Stock options outstanding	1,525,000		1,540,000		1,525,000		1,540,000
Kilroy Realty, L.P. [Member]
Numerator:
Income (loss) from continuing operations	2,683		-2,167		10,289		-4,941
Income from continuing operations attributable to noncontrolling interests in consolidated subsidiaries	-47		-48		-178		-144
Total preferred distributions	-3,312		-5,342		-9,938		-17,775
Allocation to participating securities	450	[1]	408	[1]	1,292	[1]	1,225	[1]
Numerator for basic and diluted loss from continuing operations available to common unitholders	-1,126		-7,965		-1,119		-24,085
Income from discontinued operations	6,344		4,689		11,229		88,412
Numerator for basic and diluted net income (loss) available to common unitholders	$5,218		($3,276)		$10,110		$64,327
Denominator:
Weighted average common units outstanding - basic (Note 14)	78,590,396		73,680,259		77,574,907		69,717,834
Effect of dilutive securities - contingently issuable shares and stock options	0		0		0		0
Weighted average common units outstanding - diluted (Note 14)	78,590,396		73,680,259		77,574,907		69,717,834
Basic earnings per unit:
Loss from continuing operations available to common unitholders per common unit-basic (Note 14)	($0.01)		($0.10)		($0.01)		($0.34)
Income from discontinued operations per common unit	$0.08		$0.06		$0.14		$1.26
Net income (loss) available to common unitholders per unit-basic (Note 14)	$0.07		($0.04)		$0.13		$0.92
Diluted earnings per unit:
Loss from continuing operations available to common unitholders per common unit-diluted (Note 14)	($0.01)		($0.10)		($0.01)		($0.34)
Income from discontinued operations per common unit	$0.08		$0.06		$0.14		$1.26
Net income (loss) available to common unitholders per unit-diluted (Note 14)	$0.07		($0.04)		$0.13		$0.92
Market Measure-Based Restricted Stock Units (RSUs) [Member] | Kilroy Realty, L.P. [Member]
Diluted earnings per unit:
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements, Restricted Stock Units	159,360		103,238		159,360		103,238
[1]	Participating securities include nonvested shares, time-based RSUs and vested market-measure RSUs.

Subsequent_Events_Details

Subsequent Events (Details) (USD $)	9 Months Ended		0 Months Ended	1 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Oct. 17, 2013	Oct. 29, 2013
			Subsequent Event [Member]	Subsequent Event [Member]
				acre
Subsequent Event [Line Items]
Aggregate dividends, distributions, and dividend equivalents paid to common stockholders and common unitholders	$82,152,000	$70,517,000	$29,800,000
Area of land				2
Payments to acquire land				$17,000,000