Available-For-Sale Securities Adjusted cost (Detail) (USD $)	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Cash and Cash Equivalents and Marketable Securites [Line Items]
Cost	$ 58,997,000	$ 33,037,000
Unrealized Gains	942,000	708,000
Unrealized Losses	(56,000)	(62,000)
Accrued Interest	111,000	117,000
Estimated Fair Value	59,994,000	33,800,000
Cash & Cash Equivalents	39,937,000	14,262,000	17,165,000	10,604,000
Investment Securities	20,057,000	19,538,000
Cash
Cash and Cash Equivalents and Marketable Securites [Line Items]
Cost	38,977,000	13,459,000
Unrealized Gains	0	0
Unrealized Losses	0	0
Accrued Interest	0	0
Estimated Fair Value	38,977,000	13,459,000
Cash & Cash Equivalents	38,977,000	13,459,000
Investment Securities	0	0
Fair Value, Inputs, Level 1
Cash and Cash Equivalents and Marketable Securites [Line Items]
Cost	10,051,000	11,049,000
Unrealized Gains	682,000	545,000
Unrealized Losses	(50,000)	(47,000)
Accrued Interest	34,000	43,000
Estimated Fair Value	10,717,000	11,590,000
Cash & Cash Equivalents	960,000	803,000
Investment Securities	9,757,000	10,787,000
Fair Value, Inputs, Level 1 | Money Market Accounts
Cash and Cash Equivalents and Marketable Securites [Line Items]
Cost	960,000	803,000
Unrealized Gains	0	0
Unrealized Losses	0	0
Accrued Interest	0	0
Estimated Fair Value	960,000	803,000
Cash & Cash Equivalents	960,000	803,000
Investment Securities	0	0
Fair Value, Inputs, Level 1 | Mutual Funds
Cash and Cash Equivalents and Marketable Securites [Line Items]
Cost	234,000	755,000
Unrealized Gains	13,000	17,000
Unrealized Losses	(1,000)	(8,000)
Accrued Interest	0	0
Estimated Fair Value	246,000	764,000
Cash & Cash Equivalents	0	0
Investment Securities	246,000	764,000
Fair Value, Inputs, Level 1 | Corporate Equity Securities
Cash and Cash Equivalents and Marketable Securites [Line Items]
Cost	1,853,000	1,319,000
Unrealized Gains	489,000	270,000
Unrealized Losses	(46,000)	(37,000)
Accrued Interest	0	0
Estimated Fair Value	2,296,000	1,552,000
Cash & Cash Equivalents	0	0
Investment Securities	2,296,000	1,552,000
Fair Value, Inputs, Level 1 | Government Agency Securities
Cash and Cash Equivalents and Marketable Securites [Line Items]
Cost	7,004,000	8,172,000
Unrealized Gains	180,000	258,000
Unrealized Losses	(3,000)	(2,000)
Accrued Interest	34,000	43,000
Estimated Fair Value	7,215,000	8,471,000
Cash & Cash Equivalents	0	0
Investment Securities	7,215,000	8,471,000
Fair Value, Inputs, Level 2
Cash and Cash Equivalents and Marketable Securites [Line Items]
Cost	9,969,000	8,529,000
Unrealized Gains	260,000	163,000
Unrealized Losses	(6,000)	(15,000)
Accrued Interest	77,000	74,000
Estimated Fair Value	10,300,000	8,751,000
Cash & Cash Equivalents	0	0
Investment Securities	10,300,000	8,751,000
Fair Value, Inputs, Level 2 | Municipal Bonds
Cash and Cash Equivalents and Marketable Securites [Line Items]
Cost	4,197,000	4,212,000
Unrealized Gains	124,000	119,000
Unrealized Losses	(4,000)	0
Accrued Interest	27,000	27,000
Estimated Fair Value	4,344,000	4,358,000
Cash & Cash Equivalents	0	0
Investment Securities	4,344,000	4,358,000
Fair Value, Inputs, Level 2 | Corporate Bond Securities
Cash and Cash Equivalents and Marketable Securites [Line Items]
Cost	5,772,000	4,317,000
Unrealized Gains	136,000	44,000
Unrealized Losses	(2,000)	(15,000)
Accrued Interest	50,000	47,000
Estimated Fair Value	5,956,000	4,393,000
Cash & Cash Equivalents	0	0
Investment Securities	$ 5,956,000	$ 4,393,000