Ratios and Amounts of Tier One Capital and Total Capital to Risk-Adjusted Assets and Leverage Ratios (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total risk-based capital to risk-weighted assets, actual amount	$ 79,055	$ 80,203
Tier I capital to risk-weighted assets, actual amount	52,251	53,371
Tier I capital to average assets, actual amount	52,251	53,371
Total risk-based capital to risk-weighted assets, actual ratio	10.93%	11.03%
Tier I capital to risk-weighted assets, actual ratio	7.22%	7.34%
Tier I capital to average assets, actual ratio	4.87%	4.95%
Total risk-based capital to risk-weighted assets, for capital adequacy purposes, amount	57,857	58,178
Tier I capital to risk-weighted assets, for capital adequacy purposes, amount	28,929	29,089
Tier I capital to average assets, for capital adequacy purposes, amount	42,939	43,156
Total risk-based capital to risk-weighted assets, for capital adequacy purposes, ratio	8.00%	8.00%
Tier I capital to risk-weighted assets, for capital adequacy purposes, ratio	4.00%	4.00%
Tier I capital to average assets, for capital adequacy purposes, ratio	4.00%	4.00%
Porter Bancorp and PBI Bank
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total risk-based capital to risk-weighted assets, actual amount	83,033	83,055
Total risk-based capital to risk-weighted assets, actual ratio	11.50%	11.44%
Total risk-based capital to risk-weighted assets, for capital adequacy purposes, amount	57,754	58,064
Total risk-based capital to risk-weighted assets, for capital adequacy purposes, ratio	8.00%	8.00%
Porter Bancorp
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier I capital to risk-weighted assets, actual amount	68,182	67,897
Tier I capital to risk-weighted assets, actual ratio	9.44%	9.35%
Tier I capital to risk-weighted assets, for capital adequacy purposes, amount	28,877	29,032
Tier I capital to risk-weighted assets, for capital adequacy purposes, ratio	4.00%	4.00%
PBI Bank
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total risk-based capital to risk-weighted assets, actual amount	83,033
Tier I capital to average assets, actual amount	68,182	67,897
Total risk-based capital to risk-weighted assets, actual ratio	11.50%
Tier I capital to average assets, actual ratio	6.36%	6.28%
Tier I capital to average assets, for capital adequacy purposes, amount	$ 42,880	$ 43,221
Tier I capital to average assets, for capital adequacy purposes, ratio	4.00%	4.00%