Regulatory Changes - Company's Analysis of Its Capital Position as Compared to the Basel III Requirements (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common Equity Tier 1 Capital Ratio, Amount	$ 96,461
Tier 1 Capital Ratio to Risk Weighted Assets, Amount	106,461
Minimum Total Capital Ratio to Risk Weighted Assets, Amount	113,818
Common Equity Tier 1 Capital Ratio, Ratio	16.40%
Tier 1 Capital Ratio to Risk Weighted Assets, Ratio	18.10%
Minimum Total Capital Ratio to Risk Weighted Assets, Ratio	19.30%
Consolidated [Member] | Heritage Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common Equity Tier 1 Capital Ratio, Amount	100,371
Tier 1 Capital Ratio to Risk Weighted Assets, Amount	100,371
Minimum Total Capital Ratio to Risk Weighted Assets, Amount	107,728
Common Equity Tier 1 Capital Ratio, Ratio	17.10%
Tier 1 Capital Ratio to Risk Weighted Assets, Ratio	17.10%
Minimum Total Capital Ratio to Risk Weighted Assets, Ratio	18.40%
Minimum [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common Equity Tier 1 Capital Ratio, Amount	26,495
Tier 1 Capital Ratio to Risk Weighted Assets, Amount	35,327
Minimum Total Capital Ratio to Risk Weighted Assets, Amount	47,103
Common Equity Tier 1 Capital Ratio, Ratio	4.50%
Tier 1 Capital Ratio to Risk Weighted Assets, Ratio	6.00%
Minimum Total Capital Ratio to Risk Weighted Assets, Ratio	8.00%
Minimum [Member] | Consolidated [Member] | Heritage Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common Equity Tier 1 Capital Ratio, Amount	26,402
Tier 1 Capital Ratio to Risk Weighted Assets, Amount	35,203
Minimum Total Capital Ratio to Risk Weighted Assets, Amount	46,937
Common Equity Tier 1 Capital Ratio, Ratio	4.50%
Tier 1 Capital Ratio to Risk Weighted Assets, Ratio	6.00%
Minimum Total Capital Ratio to Risk Weighted Assets, Ratio	8.00%
Minimum Including Buffer [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common Equity Tier 1 Capital Ratio, Amount	41,215
Tier 1 Capital Ratio to Risk Weighted Assets, Amount	50,047
Minimum Total Capital Ratio to Risk Weighted Assets, Amount	61,823
Common Equity Tier 1 Capital Ratio, Ratio	7.00%
Tier 1 Capital Ratio to Risk Weighted Assets, Ratio	8.50%
Minimum Total Capital Ratio to Risk Weighted Assets, Ratio	10.50%
Minimum Including Buffer [Member] | Consolidated [Member] | Heritage Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common Equity Tier 1 Capital Ratio, Amount	41,070
Tier 1 Capital Ratio to Risk Weighted Assets, Amount	49,870
Minimum Total Capital Ratio to Risk Weighted Assets, Amount	$ 61,605
Common Equity Tier 1 Capital Ratio, Ratio	7.00%
Tier 1 Capital Ratio to Risk Weighted Assets, Ratio	8.50%
Minimum Total Capital Ratio to Risk Weighted Assets, Ratio	10.50%