Loans and Other Repossessed Assets Acquired (Detail) - Consumer Credit Quality (Consumer Loan [Member], USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Consumer Credit Quality	$ 774,550	[1]	$ 782,672	[1]
Performing Financing Receivable [Member] | Home Equity Loans [Member]
Consumer Credit Quality	342,164	[1]	355,983	[1]
Performing Financing Receivable [Member] | Manufactured Housing [Member]
Consumer Credit Quality	278,329	[1]	276,522	[1]
Performing Financing Receivable [Member] | Marine [Member]
Consumer Credit Quality	79,153	[1]	75,544	[1]
Performing Financing Receivable [Member] | Other Consumer [Member]
Consumer Credit Quality	39,512	[1]	41,644	[1]
Performing Financing Receivable [Member]
Consumer Credit Quality	739,158	[1]	749,693	[1]
Performing Classified [Member] | Home Equity Loans [Member]
Consumer Credit Quality	10,226	[1]	6,858	[1]
Performing Classified [Member] | Manufactured Housing [Member]
Consumer Credit Quality	566	[1]	87	[1]
Performing Classified [Member] | Marine [Member]
Consumer Credit Quality	50	[1]	53	[1]
Performing Classified [Member] | Other Consumer [Member]
Consumer Credit Quality	93	[1]	59	[1]
Performing Classified [Member]
Consumer Credit Quality	10,935	[1]	7,057	[1]
Nonperforming Financing Receivable [Member] | Home Equity Loans [Member]
Consumer Credit Quality	9,795	[1]	10,551	[1]
Nonperforming Financing Receivable [Member] | Manufactured Housing [Member]
Consumer Credit Quality	3,219	[1]	3,491	[1]
Nonperforming Financing Receivable [Member] | Marine [Member]
Consumer Credit Quality	125	[1]	139	[1]
Nonperforming Financing Receivable [Member] | Other Consumer [Member]
Consumer Credit Quality	271	[1]	318	[1]
Nonperforming Financing Receivable [Member]
Consumer Credit Quality	13,410	[1]	14,499	[1]
Total Consumer Loans [Member] | Home Equity Loans [Member]
Consumer Credit Quality	362,185	[1]	373,392	[1]
Total Consumer Loans [Member] | Manufactured Housing [Member]
Consumer Credit Quality	282,114	[1]	280,100	[1]
Total Consumer Loans [Member] | Marine [Member]
Consumer Credit Quality	79,328	[1]	75,736	[1]
Total Consumer Loans [Member] | Other Consumer [Member]
Consumer Credit Quality	39,876	[1]	42,021	[1]
Total Consumer Loans [Member]
Consumer Credit Quality	763,503	[1]	771,249	[1]
ASC 310-30 Loans [Member] | Home Equity Loans [Member]
Consumer Credit Quality	10,923	[1]	11,272	[1]
ASC 310-30 Loans [Member] | Manufactured Housing [Member]
Consumer Credit Quality	0	[1]	0	[1]
ASC 310-30 Loans [Member] | Marine [Member]
Consumer Credit Quality	0	[1]	0	[1]
ASC 310-30 Loans [Member] | Other Consumer [Member]
Consumer Credit Quality	124	[1]	151	[1]
ASC 310-30 Loans [Member]
Consumer Credit Quality	11,047	[1]	11,423	[1]
Home Equity Loans [Member]
Consumer Credit Quality	373,108	[1]	384,664	[1]
Manufactured Housing [Member]
Consumer Credit Quality	282,114	[1]	280,100	[1]
Marine [Member]
Consumer Credit Quality	79,328	[1]	75,736	[1]
Other Consumer [Member]
Consumer Credit Quality	$ 40,000	[1]	$ 42,172	[1]

[1] Credit quality indicators are reviewed and updated as applicable on an ongoing basis in accordance with credit policies.