Retirement Benefit Plans - Fair Values Measurements of Pension Plan Assets (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of pension plan assets	$ 379,133	$ 328,060
Cash and equivalents [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of pension plan assets	4,850	12,189
Hancock Horizon Government Money Market Fund [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of pension plan assets	1,596	28,081
Cash And Money Markets [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of pension plan assets	6,446	40,270
U.S. government and agency securities and other [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of pension plan assets	54,246	44,017
Hancock Horizon Strategic Income Bond Fund [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of pension plan assets	49,192	29,895
Corporate debt securities [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of pension plan assets	39,273	33,319
Fixed Income Securities [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of pension plan assets	142,711	107,231
Hancock Horizon Quantitative Long/ Short Fund [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of pension plan assets	7,481	3,674
Hancock Horizon Diversified International Fund [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of pension plan assets	32,984	24,528
Hancock Horizon Burkenroad Fund [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of pension plan assets	3,863	2,414
Hancock Horizon Growth Fund [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of pension plan assets	27,332	13,403
Hancock Horizon Diversified Value Fund [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of pension plan assets	28,543	19,742
Equity securities-large cap [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of pension plan assets	87,769	72,607
Equity securities-small cap [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of pension plan assets	42,004	44,191
Equity securities [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of pension plan assets	229,976	180,559
Level 1 [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of pension plan assets	296,019	265,756
Level 1 [Member] | Cash and equivalents [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of pension plan assets	4,850	12,189
Level 1 [Member] | Hancock Horizon Government Money Market Fund [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of pension plan assets	1,596	28,081
Level 1 [Member] | Cash And Money Markets [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of pension plan assets	6,446	40,270
Level 1 [Member] | U.S. government and agency securities and other [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of pension plan assets	10,405	15,032
Level 1 [Member] | Hancock Horizon Strategic Income Bond Fund [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of pension plan assets	49,192	29,895
Level 1 [Member] | Fixed Income Securities [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of pension plan assets	59,597	44,927
Level 1 [Member] | Hancock Horizon Quantitative Long/ Short Fund [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of pension plan assets	7,481	3,674
Level 1 [Member] | Hancock Horizon Diversified International Fund [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of pension plan assets	32,984	24,528
Level 1 [Member] | Hancock Horizon Burkenroad Fund [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of pension plan assets	3,863	2,414
Level 1 [Member] | Hancock Horizon Growth Fund [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of pension plan assets	27,332	13,403
Level 1 [Member] | Hancock Horizon Diversified Value Fund [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of pension plan assets	28,543	19,742
Level 1 [Member] | Equity securities-large cap [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of pension plan assets	87,769	72,607
Level 1 [Member] | Equity securities-small cap [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of pension plan assets	42,004	44,191
Level 1 [Member] | Equity securities [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of pension plan assets	229,976	180,559
Level 2 [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of pension plan assets	83,114	62,304
Level 2 [Member] | U.S. government and agency securities and other [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of pension plan assets	43,841	28,985
Level 2 [Member] | Corporate debt securities [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of pension plan assets	39,273	33,319
Level 2 [Member] | Fixed Income Securities [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value of pension plan assets	$ 83,114	$ 62,304