Supplemental Cash Flow Information of the Operating Partnership - Supplemental Cash Flow (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Jan. 01, 2019
SUPPLEMENTAL CASH FLOWS INFORMATION:
Cash paid for interest, net of capitalized interest of $20,403 and $18,901 as of March 31, 2020 and 2019, respectively	$ 10,035	$ 4,706
Capitalized interest	20,403	18,901
Cash paid for amounts included in the measurement of ground lease liabilities	1,332	1,220
NON-CASH INVESTING TRANSACTIONS:
Accrual for expenditures for operating properties and development properties	129,251	87,038
Tenant improvements funded directly by tenants	2,081	2,682
Initial measurement of operating right of use ground lease assets	96,145		$ 96,348	$ 82,938
Initial measurement of operating ground lease liabilities	98,247		98,400	87,409
NON-CASH FINANCING TRANSACTIONS:
Accrual of distributions payable to common unitholders (Notes 6 and 15)	57,620	47,676
Kilroy Realty L.P. [Member]
SUPPLEMENTAL CASH FLOWS INFORMATION:
Cash paid for interest, net of capitalized interest of $20,403 and $18,901 as of March 31, 2020 and 2019, respectively	10,035	4,706
Capitalized interest	20,403	18,901
Cash paid for amounts included in the measurement of ground lease liabilities	1,332	1,220
NON-CASH INVESTING TRANSACTIONS:
Accrual for expenditures for operating properties and development properties	129,251	87,038
Tenant improvements funded directly by tenants	2,081	2,682
Initial measurement of operating right of use ground lease assets	96,145		96,348	82,938
Initial measurement of operating ground lease liabilities	98,247		$ 98,400	$ 87,409
NON-CASH FINANCING TRANSACTIONS:
Accrual of distributions payable to common unitholders (Notes 6 and 15)	$ 57,620	$ 47,676