Loans - Investment in Loans by Portfolio Segment and Based on Impairment (Detail) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance, Beginning balance	$ 19,037,000	$ 30,933,000	$ 21,130,000	$ 42,271,000	$ 42,271,000
Loans individually evaluated for impairment	2,423,000		2,423,000		3,024,000
Provision	657,000	30,279,000	3,834,000	37,223,000
Loans collectively evaluated for impairment	18,609,000		18,609,000		18,106,000
Chargeoffs	(1,104,000)	(3,882,000)	(7,854,000)	(22,946,000)	0
Allowance, Ending balance	21,032,000	20,048,000	21,032,000	20,048,000	21,130,000
Recoveries	2,442,000	876,000	3,922,000	1,658,000
Loans individually evaluated for impairment	46,327,000		46,327,000		61,017,000
Net (chargeoffs) recovery from asset sale		(38,158,000)		(38,158,000)
Loans collectively evaluated for impairment	982,608,000		982,608,000		1,025,139,000
Allowance, Ending balance	21,032,000	20,048,000	21,032,000	20,048,000	21,130,000
Ending balance	1,028,935,000		1,028,935,000		1,086,156,000
Permanent Real Estate Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance, Beginning balance	12,129,000	22,121,000	13,819,000	31,323,000	31,323,000
Loans individually evaluated for impairment	1,222,000		1,222,000		2,380,000
Provision	2,286,000	27,905,000	5,064,000	32,539,000
Loans collectively evaluated for impairment	12,634,000		12,634,000		11,439,000
Chargeoffs	(651,000)	(2,267,000)	(5,794,000)	(16,328,000)
Allowance, Ending balance	13,856,000	12,483,000	13,856,000	12,483,000
Recoveries	92,000	468,000	767,000	693,000
Loans individually evaluated for impairment	26,259,000		26,259,000		43,013,000
Net (chargeoffs) recovery from asset sale		(35,744,000)		(35,744,000)
Loans collectively evaluated for impairment	742,473,000		742,473,000		769,155,000
Allowance, Ending balance	13,856,000	12,483,000	13,856,000	12,483,000
Ending balance	768,732,000		768,732,000		812,168,000
Construction Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance, Beginning balance	1,803,000	2,490,000	1,404,000	4,493,000	4,493,000
Loans individually evaluated for impairment	677,000		677,000		478,000
Provision	(1,800,000)	1,678,000	(1,354,000)	2,293,000
Loans collectively evaluated for impairment	1,202,000		1,202,000		926,000
Chargeoffs	(37,000)	(543,000)	(402,000)	(3,213,000)
Allowance, Ending balance	1,879,000	1,630,000	1,879,000	1,630,000
Recoveries	1,913,000	139,000	2,231,000	191,000
Loans individually evaluated for impairment	3,333,000		3,333,000		7,547,000
Net (chargeoffs) recovery from asset sale		(2,134,000)		(2,134,000)
Loans collectively evaluated for impairment	35,599,000		35,599,000		25,305,000
Allowance, Ending balance	1,879,000	1,630,000	1,879,000	1,630,000
Ending balance	38,932,000		38,932,000		32,852,000
Consumer Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance, Beginning balance	4,202,000	4,805,000	4,459,000	4,576,000	4,576,000
Loans individually evaluated for impairment	524,000		524,000
Provision	394,000	1,288,000	967,000	2,422,000
Loans collectively evaluated for impairment	3,929,000		3,929,000		4,459,000
Chargeoffs	(400,000)	(839,000)	(1,514,000)	(2,198,000)
Allowance, Ending balance	4,453,000	4,557,000	4,453,000	4,557,000
Recoveries	257,000	125,000	541,000	579,000
Loans individually evaluated for impairment	12,407,000		12,407,000		8,784,000
Net (chargeoffs) recovery from asset sale		(822,000)		(822,000)
Loans collectively evaluated for impairment	181,976,000		181,976,000		205,809,000
Allowance, Ending balance	4,453,000	4,557,000	4,453,000	4,557,000
Ending balance	194,383,000		194,383,000		214,593,000
Commercial Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance, Beginning balance	903,000	1,517,000	1,448,000	1,879,000	1,879,000
Loans individually evaluated for impairment					166,000
Provision	(223,000)	(592,000)	(843,000)	(31,000)
Loans collectively evaluated for impairment	844,000		844,000		1,282,000
Chargeoffs	(16,000)	(233,000)	(144,000)	(1,207,000)
Allowance, Ending balance	844,000	1,378,000	844,000	1,378,000
Recoveries	180,000	144,000	383,000	195,000
Loans individually evaluated for impairment	4,328,000		4,328,000		1,673,000
Net (chargeoffs) recovery from asset sale		542,000		542,000
Loans collectively evaluated for impairment	22,560,000		22,560,000		24,870,000
Allowance, Ending balance	844,000	1,378,000	844,000	1,378,000
Ending balance	$ 26,888,000		$ 26,888,000		$ 26,543,000