CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
REVENUES (Note 2):
Revenues	$ 837,454	$ 747,298	$ 719,001
EXPENSES:
Real estate taxes (Note 2)	78,097	70,820	66,449
Provision for bad debts (Notes 2 and 20)	0	5,685	3,269
Ground leases (Notes 2, 5 and 18)	8,113
Ground leases (Notes 2, 5 and 18)		6,176	6,337
General and administrative expenses (Note 15)	88,139	90,471	60,581
Leasing costs (Notes 2 and 5)	7,615
Depreciation and amortization (Notes 2 and 5)	273,130	254,281	245,886
Total expenses	615,131	561,220	512,493
OTHER (EXPENSES) INCOME:
Interest income and other net investment gain (loss) (Note 19)	4,641	(559)	5,503
Interest expense (Note 9)	(48,537)	(49,721)	(66,040)
Loss on early extinguishment of debt (Note 9)	0	(12,623)	(5,312)
Net gain on sales of land (Note 4)	0	11,825	449
Gains on sales of depreciable operating properties (Note 4)	36,802	142,926	39,507
Total other (expenses) income	(7,094)	91,848	(25,893)
NET INCOME	215,229	277,926	180,615
Net income attributable to noncontrolling common units of the Operating Partnership (Notes 2 and 11)	(3,766)	(5,193)	(3,223)
Net income attributable to noncontrolling interests in consolidated property partnerships (Notes 2 and 11)	(16,020)	(14,318)	(12,780)
Total income attributable to noncontrolling interests	(19,786)	(19,511)	(16,003)
NET INCOME ATTRIBUTABLE TO KILROY REALTY CORPORATION / KILROY REALTY, L.P.	195,443	258,415	164,612
Preferred dividends (Note 13)	0	0	(5,774)
Original issuance costs of redeemed preferred stock and preferred units (Note 13)	0	0	(7,589)
Total preferred dividends	0	0	(13,363)
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS (UNITHOLDERS)	$ 195,443	$ 258,415	$ 151,249
Net income available to common stockholders per share - basic (in dollars per share)	$ 1.87	$ 2.56	$ 1.52
Net income available to common stockholders per share - diluted (in dollars per share)	$ 1.86	$ 2.55	$ 1.51
Weighted average shares of common stock outstanding – basic (in shares)	103,200,568	99,972,359	98,113,561
Weighted average shares of common stock outstanding – diluted (in shares)	103,849,168	100,482,365	98,727,331
Rental income [Member]
REVENUES (Note 2):
Revenues	$ 826,472	$ 656,631	$ 633,896
Tenant reimbursements [Member]
REVENUES (Note 2):
Revenues	0	80,982	76,559
Other property income [Member]
REVENUES (Note 2):
Revenues	10,982	9,685	8,546
Property [Member]
EXPENSES:
Property expenses (Note 2)	$ 160,037	$ 133,787	$ 129,971