Bank of Hawaii Corporation Financial Statements - Schedule of Condensed Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating Activities
Net Income	$ 153,804	$ 225,913	$ 219,602
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities:
Share-Based Compensation	7,578	8,337	8,146
Net (Gains) Losses on Investment Securities	(9,932)	3,986	3,938
Net Change in Other Assets and Other Liabilities	(127,934)	(20,039)	27,815
Net Cash Provided by Operating Activities	146,416	234,238	317,922
Investing Activities
Purchases	(1,661,180)	(1,380,430)	(419,640)
Net Cash Used in Investing Activities	(2,373,282)	(773,268)	(74,668)
Financing Activities
Proceeds from Issuance of Common Stock	9,389	7,872	7,873
Repurchase of Common Stock	(18,006)	(137,649)	(91,988)
Cash Dividends Paid	(107,434)	(105,478)	(98,496)
Net Cash Provided by (Used in) Financing Activities	2,282,296	571,719	(165,136)
Net Change in Cash and Cash Equivalents	55,430	32,689	78,118
Cash and Cash Equivalents at Beginning of Period	558,658	525,969	447,851
Cash and Cash Equivalents at End of Period	614,088	558,658	525,969
Parent Company
Operating Activities
Net Income	153,804	225,913	219,602
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities:
Share-Based Compensation	795	760	630
Net (Gains) Losses on Investment Securities	(13,336)	850	819
Equity in Undistributed Income of Subsidiaries	(11,331)	(7,134)	(35,429)
Net Change in Other Assets and Other Liabilities	(68)	(135)	870
Net Cash Provided by Operating Activities	129,864	220,254	186,492
Investing Activities
Proceeds from (Expenses related to) Sales of Investment Securities	18,336	4,259	(819)
Purchases	(2,501)	(4,933)
Net Cash Used in Investing Activities	15,835	(674)	(819)
Financing Activities
Proceeds from Issuance of Common Stock	9,389	7,872	7,873
Repurchase of Common Stock	(18,006)	(137,649)	(91,988)
Cash Dividends Paid	(107,434)	(105,478)	(98,496)
Net Cash Provided by (Used in) Financing Activities	(116,051)	(235,255)	(182,611)
Net Change in Cash and Cash Equivalents	29,648	(15,675)	3,062
Cash and Cash Equivalents at Beginning of Period	37,056	52,731	49,669
Cash and Cash Equivalents at End of Period	$ 66,704	$ 37,056	$ 52,731