REGULATORY MATTERS - Capital amounts and ratios for Bank (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Bankwell Bank
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital to Risk-Weighted Assets, Actual Capital, Amount	$ 112,989	$ 66,674
Total Capital to Risk-Weighted Assets, Actual Capital, Ratio	15.27%	10.74%
Total Capital to Risk-Weighted Assets, For Capital Adequacy Purposes, Amount	59,199	49,682
Total Capital to Risk-Weighted Assets, For Capital Adequacy Purposes, Ratio	8.00%	8.00%
Total Capital to Risk-Weighted Assets, To be Well Capitalized Under Prompt Corrective Action Provisions, Amount	73,999	62,103
Total Capital to Risk-Weighted Assets, To be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	10.00%	10.00%
Tier I Capital to Risk-Weighted Assets, Actual Capital, Amount	103,735	58,908
Tier I Capital to Risk-Weighted Assets, Actual Capital, Ratio	14.02%	9.49%
Tier I Capital to Risk-Weighted Assets, For Capital Adequacy Purposes, Amount	29,599	24,841
Tier I Capital to Risk-Weighted Assets, For Capital Adequacy Purposes, Ratio	4.00%	4.00%
Tier I Capital to Risk-Weighted Assets, To be Well Capitalized Under Prompt Corrective Action Provisions, Amount	44,399	37,262
Tier I Capital to Risk-Weighted AssetsTo be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	6.00%	6.00%
Tier I Capital to Average Assets, Actual Capital, Amount	103,735	58,908
Tier I Capital to Average Assets, Actual Capital, Ratio	11.93%	7.91%
Tier I Capital to Average Assets, For Capital Adequacy Purposes, Amount	34,793	29,772
Tier I Capital to Average Assets, For Capital Adequacy Purposes, Ratio	4.00%	4.00%
Tier I Capital to Average Assets, To be Well Capitalized Under Prompt Corrective Action Provisions, Amount	43,491	37,215
Tier I Capital to Average Assets, To be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	5.00%	5.00%
Bankwell Financial Group Inc.
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital to Risk-Weighted Assets, Actual Capital, Amount	126,846	76,537
Total Capital to Risk-Weighted Assets, Actual Capital, Ratio	16.96%	12.32%
Total Capital to Risk-Weighted Assets, For Capital Adequacy Purposes, Amount	59,829	49,683
Total Capital to Risk-Weighted Assets, For Capital Adequacy Purposes, Ratio	8.00%	8.00%
Total Capital to Risk-Weighted Assets, To be Well Capitalized Under Prompt Corrective Action Provisions, Amount
Total Capital to Risk-Weighted Assets, To be Well Capitalized Under Prompt Corrective Action Provisions, Ratio
Tier I Capital to Risk-Weighted Assets, Actual Capital, Amount	117,495	68,766
Tier I Capital to Risk-Weighted Assets, Actual Capital, Ratio	15.71%	11.07%
Tier I Capital to Risk-Weighted Assets, For Capital Adequacy Purposes, Amount	29,914	24,841
Tier I Capital to Risk-Weighted Assets, For Capital Adequacy Purposes, Ratio	4.00%	4.00%
Tier I Capital to Risk-Weighted Assets, To be Well Capitalized Under Prompt Corrective Action Provisions, Amount
Tier I Capital to Risk-Weighted AssetsTo be Well Capitalized Under Prompt Corrective Action Provisions, Ratio
Tier I Capital to Average Assets, Actual Capital, Amount	117,495	68,766
Tier I Capital to Average Assets, Actual Capital, Ratio	13.38%	9.15%
Tier I Capital to Average Assets, For Capital Adequacy Purposes, Amount	35,131	30,068
Tier I Capital to Average Assets, For Capital Adequacy Purposes, Ratio	4.00%	4.00%
Tier I Capital to Average Assets, To be Well Capitalized Under Prompt Corrective Action Provisions, Amount
Tier I Capital to Average Assets, To be Well Capitalized Under Prompt Corrective Action Provisions, Ratio