Supplemental Cash Flow Information of the Operating Partnership - Reconciliation of Cash and Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH:
Cash and cash equivalents	$ 52,415	$ 51,604	$ 50,817	$ 57,649
Restricted cash	6,300	119,430	0	9,149
Cash and cash equivalents and restricted cash	58,715	171,034	50,817	66,798
Kilroy Realty L.P. [Member]
RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH:
Cash and cash equivalents	52,415	51,604		57,649
Restricted cash	6,300	119,430	0	9,149
Cash and cash equivalents and restricted cash	$ 58,715	$ 171,034	$ 50,817	$ 66,798