Loans and Other Repossessed Assets Acquired (Detail) - Loan portfolio by age of delinquency (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
30-59 Days Past Due	$ 10,956		$ 11,342
60-89 Days Past Due	2,784		5,740
90 Days and Greater Past Due	44,910		45,891
90 Days and Greater Accruing	6		43
Total Past Due	58,656		63,016
Current	2,417,486	[1]	2,432,308	[2]
Total Loans	2,476,142		2,495,324
Home Equity Loans [Member]
30-59 Days Past Due	2,430		2,328
60-89 Days Past Due	328		2,086
90 Days and Greater Past Due	9,295		10,049
90 Days and Greater Accruing	0		0
Total Past Due	12,053		14,463
Current	361,055	[1]	370,201	[2]
Total Loans	373,108		384,664
Manufactured Housing [Member]
30-59 Days Past Due	973		2,479
60-89 Days Past Due	189		762
90 Days and Greater Past Due	3,085		3,355
90 Days and Greater Accruing	0		0
Total Past Due	4,247		6,596
Current	277,867	[1]	273,504	[2]
Total Loans	282,114		280,100
Marine [Member]
30-59 Days Past Due	112		216
60-89 Days Past Due	42		68
90 Days and Greater Past Due	125		139
90 Days and Greater Accruing	0		0
Total Past Due	279		423
Current	79,049	[1]	75,313	[2]
Total Loans	79,328		75,736
Other Consumer [Member]
30-59 Days Past Due	140		261
60-89 Days Past Due	37		123
90 Days and Greater Past Due	265		275
90 Days and Greater Accruing	6		43
Total Past Due	448		702
Current	39,552	[1]	41,470	[2]
Total Loans	40,000		42,172
Total Consumer Loans [Member]
30-59 Days Past Due	3,655		5,284
60-89 Days Past Due	596		3,039
90 Days and Greater Past Due	12,770		13,818
90 Days and Greater Accruing	6		43
Total Past Due	17,027		22,184
Current	757,523	[1]	760,488	[2]
Total Loans	774,550		782,672
Commercial Business [Member]
30-59 Days Past Due	1,199		761
60-89 Days Past Due	56		86
90 Days and Greater Past Due	1,813		1,460
90 Days and Greater Accruing	0		0
Total Past Due	3,068		2,307
Current	127,101	[1]	116,072	[2]
Total Loans	130,169		118,379
Commercial Real Estate [Member]
30-59 Days Past Due	3,091		2,380
60-89 Days Past Due	1,161		1,112
90 Days and Greater Past Due	18,213		18,386
90 Days and Greater Accruing	0		0
Total Past Due	22,465		21,878
Current	445,425	[1]	469,689	[2]
Total Loans	467,890		491,567
Commercial Construction [Member]
30-59 Days Past Due	0		0
60-89 Days Past Due	0		0
90 Days and Greater Past Due	0		247
90 Days and Greater Accruing	0		0
Total Past Due	0		247
Current	1,092	[1]	817	[2]
Total Loans	1,092		1,064
Commercial Land [Member]
30-59 Days Past Due	1,321		966
60-89 Days Past Due	219		607
90 Days and Greater Past Due	3,845		4,058
90 Days and Greater Accruing	0		0
Total Past Due	5,385		5,631
Current	59,197	[1]	64,478	[2]
Total Loans	64,582		70,109
Total Commercial Loans [Member]
30-59 Days Past Due	5,611		4,107
60-89 Days Past Due	1,436		1,805
90 Days and Greater Past Due	23,871		24,151
90 Days and Greater Accruing	0		0
Total Past Due	30,918		30,063
Current	632,815	[1]	651,056	[2]
Total Loans	663,733		681,119
Residential 1-4 Family [Member]
30-59 Days Past Due	821		1,943
60-89 Days Past Due	612		857
90 Days and Greater Past Due	7,693		7,137
90 Days and Greater Accruing	0		0
Total Past Due	9,126		9,937
Current	953,927	[1]	946,418	[2]
Total Loans	963,053		956,355
Residential Construction [Member]
30-59 Days Past Due	284		0
60-89 Days Past Due	0		0
90 Days and Greater Past Due	0		0
90 Days and Greater Accruing	0		0
Total Past Due	284		0
Current	25,611	[1]	22,439	[2]
Total Loans	25,895		22,439
Residential Land [Member]
30-59 Days Past Due	585		8
60-89 Days Past Due	140		39
90 Days and Greater Past Due	576		785
90 Days and Greater Accruing	0		0
Total Past Due	1,301		832
Current	47,610	[1]	51,907	[2]
Total Loans	48,911		52,739
Total Residential Loans [Member]
30-59 Days Past Due	1,690		1,951
60-89 Days Past Due	752		896
90 Days and Greater Past Due	8,269		7,922
90 Days and Greater Accruing	0		0
Total Past Due	10,711		10,769
Current	1,027,148	[1]	1,020,764	[2]
Total Loans	1,037,859		1,031,533
Acquired Non-Covered Loans [Member]
30-59 Days Past Due	28		153
60-89 Days Past Due	0		329
90 Days and Greater Past Due	235		328
90 Days and Greater Accruing	0		0
Total Past Due	263		810
Current	111,837	[1]	117,321	[2]
Total Loans	112,100		118,131
Acquired Covered Loans [Member]
30-59 Days Past Due	2,951		1,472
60-89 Days Past Due	414		173
90 Days and Greater Past Due	8,769		8,649
90 Days and Greater Accruing	0		0
Total Past Due	12,134		10,294
Current	189,052	[1]	206,395	[2]
Total Loans	201,186		216,689
Legacy Loans [Member]
30-59 Days Past Due	7,977		9,717
60-89 Days Past Due	2,370		5,238
90 Days and Greater Past Due	35,906		36,914
90 Days and Greater Accruing	6		43
Total Past Due	46,259		51,912
Current	2,116,597	[1]	2,108,592	[2]
Total Loans	$ 2,162,856		$ 2,160,504

[1] Included in current loans are $3.8 million of accruing performing TDRs. Accruing TDRs include $257 thousand in residential land, $683 thousand in commercial business, $1.7 million in commercial real estate, $499 thousand in commercial land, $500 thousand in home equity and $134 thousand in manufactured housing.

[2] Included in current loans are $3.5 million of accruing performing TDRs. Accruing TDRs include $687 thousand in commercial business, $1.7 million in commercial real estate, $502 thousand in home equity, $499 thousand in commercial land and $135 thousand in manufactured housing.