Supplemental Cash Flow Information of the Operating Partnership - Supplemental Cash Flow (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jan. 01, 2019
SUPPLEMENTAL CASH FLOWS INFORMATION:
Cash paid for interest, net of capitalized interest of $38,780 and $28,267 as of June 30, 2019 and 2018, respectively	$ 23,009	$ 25,136
Capitalized interest	38,780	28,267
Cash paid for amounts included in the measurement of ground lease liabilities	2,699	2,349
NON-CASH INVESTING TRANSACTIONS:
Accrual for expenditures for operating properties and development properties	129,500	80,198
Assumption of accrued liabilities in connection with acquisitions	0	40,624
Tenant improvements funded directly by tenants	7,017	4,611
Operating right of use ground lease asset	82,647		$ 82,938
Operating ground lease liabilities	87,082		87,409
NON-CASH FINANCING TRANSACTIONS:
Accrual of distributions payable to common unitholders	50,800	47,348
Kilroy Realty L.P. [Member]
SUPPLEMENTAL CASH FLOWS INFORMATION:
Cash paid for interest, net of capitalized interest of $38,780 and $28,267 as of June 30, 2019 and 2018, respectively	23,009	25,136
Capitalized interest	38,780	28,267
Cash paid for amounts included in the measurement of ground lease liabilities	2,699	2,349
NON-CASH INVESTING TRANSACTIONS:
Accrual for expenditures for operating properties and development properties	129,500	80,198
Assumption of accrued liabilities in connection with acquisitions	0	40,624
Tenant improvements funded directly by tenants	7,017	4,611
Operating right of use ground lease asset	82,647		82,938
Operating ground lease liabilities	87,082		$ 87,409
NON-CASH FINANCING TRANSACTIONS:
Accrual of distributions payable to common unitholders	$ 50,800	$ 47,348