Stockholders' Equity - Schedule of Compliance with Regulatory Capital Requirements (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Hancock [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total capital (to risk weighted assets), Actual, Amount	$ 1,945,710	$ 1,877,832
Tier 1 capital (to risk weighted assets), Actual, Amount	1,777,348	1,685,058
Tier 1 leverage capital Actual, Amount	1,777,348	1,685,058
Total capital (to risk weighted assets), Actual, Ratio %	12.30%	13.11%
Tier 1 capital (to risk weighted assets), Actual, Ratio %	11.23%	11.76%
Tier 1 leverage capital, Actual, Ratio %	9.17%	9.34%
Total capital (to risk weighted assets), Required for Minimum Capital Adequacy, Amount	1,265,796	1,146,061
Tier 1 capital (to risk weighted assets), Required for Minimum Capital Adequacy, Amount	632,898	573,030
Tier 1 leverage capital, Required for Minimum Capital Adequacy, Amount	581,263	541,066
Total capital (to risk weighted assets), Required for Minimum Capital Adequacy, Ratio %	8.00%	8.00%
Tier 1 capital (to risk weighted assets), Required for Minimum Capital Adequacy, Ratio %	4.00%	4.00%
Tier 1 leverage capital, Required for Minimum Capital Adequacy, Ratio %	3.00%	3.00%
Total capital (to risk weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio %	10.00%
Tier 1 capital (to risk weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio %	6.00%
Tier 1 leverage capital, To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio %	5.00%
Hancock Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total capital (to risk weighted assets), Actual, Amount		636,871
Tier 1 capital (to risk weighted assets), Actual, Amount		577,280
Tier 1 leverage capital Actual, Amount		577,280
Total capital (to risk weighted assets), Actual, Ratio %		13.48%
Tier 1 capital (to risk weighted assets), Actual, Ratio %		12.21%
Tier 1 leverage capital, Actual, Ratio %		9.01%
Total capital (to risk weighted assets), Required for Minimum Capital Adequacy, Amount		378,093
Tier 1 capital (to risk weighted assets), Required for Minimum Capital Adequacy, Amount		189,047
Tier 1 leverage capital, Required for Minimum Capital Adequacy, Amount		192,137
Total capital (to risk weighted assets), Required for Minimum Capital Adequacy, Ratio %		8.00%
Tier 1 capital (to risk weighted assets), Required for Minimum Capital Adequacy, Ratio %		4.00%
Tier 1 leverage capital, Required for Minimum Capital Adequacy, Ratio %		3.00%
Total capital (to risk weighted assets), To Be Well Capitalized Under Prompt Correct Action Provisions, Amount		472,617
Tier 1 capital (to risk weighted assets), To Be Well Capitalized Under Prompt Correct Action Provisions, Amount		283,570
Tier 1 leverage capital, To Be Well Capitalized Under Prompt Correct Action Provisions, Amount		320,228
Total capital (to risk weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio %		10.00%
Tier 1 capital (to risk weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio %		6.00%
Tier 1 leverage capital, To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio %		5.00%
Whitney Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total capital (to risk weighted assets), Actual, Amount	1,925,175	1,187,699
Tier 1 capital (to risk weighted assets), Actual, Amount	1,756,813	1,088,339
Tier 1 leverage capital Actual, Amount	1,756,813	1,088,339
Total capital (to risk weighted assets), Actual, Ratio %	12.20%	12.25%
Tier 1 capital (to risk weighted assets), Actual, Ratio %	11.13%	11.22%
Tier 1 leverage capital, Actual, Ratio %	9.13%	9.02%
Total capital (to risk weighted assets), Required for Minimum Capital Adequacy, Amount	1,262,439	775,709
Tier 1 capital (to risk weighted assets), Required for Minimum Capital Adequacy, Amount	631,220	387,854
Tier 1 leverage capital, Required for Minimum Capital Adequacy, Amount	577,493	361,878
Total capital (to risk weighted assets), Required for Minimum Capital Adequacy, Ratio %	8.00%	8.00%
Tier 1 capital (to risk weighted assets), Required for Minimum Capital Adequacy, Ratio %	4.00%	4.00%
Tier 1 leverage capital, Required for Minimum Capital Adequacy, Ratio %	3.00%	3.00%
Total capital (to risk weighted assets), To Be Well Capitalized Under Prompt Correct Action Provisions, Amount	1,578,049	969,636
Tier 1 capital (to risk weighted assets), To Be Well Capitalized Under Prompt Correct Action Provisions, Amount	946,829	581,782
Tier 1 leverage capital, To Be Well Capitalized Under Prompt Correct Action Provisions, Amount	$ 962,488	$ 603,129
Total capital (to risk weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio %	10.00%	10.00%
Tier 1 capital (to risk weighted assets), To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio %	6.00%	6.00%
Tier 1 leverage capital, To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio %	5.00%	5.00%