Retirement Benefit Plans - Additional Information (Detail) - USD ($) $ in Thousands		12 Months Ended
	Dec. 31, 2007	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Period of employment required to cover employee stock purchase plan		60 days
Percentage of compensation saved by participant for which employer contributes hundred percent		100.00%
Employer matching contribution for first one percent of compensation saved		1.00%
Percentage of compensation saved by participant for which employer contributes fifty percent		50.00%
Employer matching contribution for next five percent of compensation saved		5.00%
Initial saving rate for employees not participating in plan		3.00%
Estimated amounts of actuarial loss that will be amortized from AOCI into net periodic benefit cost over the next year		$ 5,500
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions		86,123	$ 1,123
Funded status at end of year-net asset (liability)		28,731	$ (18,203)
Defined benefit plan, excess of plan assets over the benefit obligation		44,000
Defined Benefit Plan, Unfunded Benefit Obligation		$ 15,300
Hancock Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Minimum age for increase in per capita cost of health care benefit		55 years
Year of service who have reached 55 years of age		10 years
Increase (decrease) in pre- and post-medicare age health costs rate		7.50%
Decrease in ultimate rate over a period of time		5.00%
Defined benefit plan mortality assumption period			7 years
Whitney 401K Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Minimum age for increase in per capita cost of health care benefit	55 years
Year of service who have reached 55 years of age	10 years
Hancock 401k Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions		$ 7,400	$ 7,100	$ 7,000