Retirement and Employee Benefit Plans (Details 1) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Hancock Plan [Member]
Weighted average assumptions as of measurement date
Discount rate for benefit obligations		5.30%
Whitney Plan [Member]
Weighted average assumptions as of measurement date
Discount rate for benefit obligations	4.10%
Defined Benefit Plan-Pension [Member] | Hancock Plan [Member]
Net periodic benefit cost
Service cost	$ 4,689	$ 3,500	$ 3,107
Interest cost	5,453	5,233	4,833
Expected return on plan assets	(5,490)	(4,646)	(3,873)
Recognized net amortization and deferral	2,343	2,281	2,648
Net periodic benefit cost	6,995	6,368	6,715
Other changes in plan assets and benefit obligations recognized in other comprehensive income, before taxes
Net (loss)/gain recognized during the year	(2,343)	(2,281)	(2,648)
Total recognized in other comprehensive income	29,446	2,057	(3,737)
Total recognized in net periodic benefit cost and other comprehensive income	36,441	8,425	2,978
Weighted average assumptions as of measurement date
Discount rate for benefit obligations	4.35%	5.46%	5.95%
Discount rate for net periodic benefit cost	5.46%	5.95%	5.96%
Expected long-term return on plan assets	7.50%	7.50%	7.50%
Rate of compensation increase	4.00%	4.00%	4.00%
Defined Benefit Plan-Pension [Member] | Whitney Plan [Member] | Qualified [Member]
Net periodic benefit cost
Service cost	3,751
Interest cost	6,664
Expected return on plan assets	(9,628)
Recognized net amortization and deferral
Net periodic benefit cost	787
Other changes in plan assets and benefit obligations recognized in other comprehensive income, before taxes
Net (loss)/gain recognized during the year
Total recognized in other comprehensive income	55,524
Total recognized in net periodic benefit cost and other comprehensive income	56,311
Weighted average assumptions as of measurement date
Discount rate for benefit obligations	4.31%
Discount rate for net periodic benefit cost	5.35%
Expected long-term return on plan assets	7.50%
Rate of compensation increase	3.58%
Defined Benefit Plan-Pension [Member] | Whitney Plan [Member] | Nonqualified [Member]
Net periodic benefit cost
Service cost	27
Interest cost	438
Expected return on plan assets
Recognized net amortization and deferral
Net periodic benefit cost	465
Other changes in plan assets and benefit obligations recognized in other comprehensive income, before taxes
Net (loss)/gain recognized during the year
Total recognized in other comprehensive income	1,597
Total recognized in net periodic benefit cost and other comprehensive income	2,062
Weighted average assumptions as of measurement date
Discount rate for benefit obligations	4.31%
Discount rate for net periodic benefit cost	5.35%
Rate of compensation increase	3.58%
Defined Benefit Plan-Postretirement [Member]
Weighted average assumptions as of measurement date
Discount rate for benefit obligations	4.25%
Defined Benefit Plan-Postretirement [Member] | Hancock Plan [Member]
Net periodic benefit cost
Service cost	137	124	114
Interest cost	611	556	565
Amortization of net loss	538	302	296
Amortization of prior service cost	(48)	(48)	(48)
Net periodic benefit cost	1,238	934	927
Other changes in plan assets and benefit obligations recognized in other comprehensive income, before taxes
Net (loss)/gain recognized during the year	(538)	(302)	(296)
Net actuarial (gain)/loss	4,293	2,098	1,574
Amortization of prior service cost	48	48	48
Total recognized in other comprehensive income	3,803	1,844	1,326
Total recognized in net periodic benefit cost and other comprehensive income	5,041	2,778	2,253
Defined Benefit Plan-Postretirement [Member] | Whitney Plan [Member]
Net periodic benefit cost
Service cost
Interest cost	480
Amortization of net loss
Amortization of prior service cost
Net periodic benefit cost	480
Other changes in plan assets and benefit obligations recognized in other comprehensive income, before taxes
Net (loss)/gain recognized during the year
Amortization of prior service cost
Total recognized in other comprehensive income	1,645
Total recognized in net periodic benefit cost and other comprehensive income	$ 2,125