Retirement and Employee Benefit Plans (Details 5) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011
Hancock Plan [Member]
Assumed health care cost trend rates
Aggregated service and interest cost, 1% decrease in rates	$ 654
Aggregated service and interest cost, assumed rates	748
Aggregated service and interest cost, 1% increase in rates	866
Postretirement benefit obligation, 1% decrease in rates	14,655
Postretirement benefit obligation, assumed rates	16,653
Postretirement benefit obligation, 1% increase in rates	19,114
Whitney Plan [Member]
Assumed health care cost trend rates
Aggregated service and interest cost, 1% decrease in rates	431
Aggregated service and interest cost, assumed rates	480
Aggregated service and interest cost, 1% increase in rates	538
Postretirement benefit obligation, 1% decrease in rates	15,620
Postretirement benefit obligation, assumed rates	17,454
Postretirement benefit obligation, 1% increase in rates	$ 19,631