Available-For-Sale Securities Adjusted cost (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash and Cash Equivalents and Marketable Securities [Line Items]
Cost	$ 51,833,000	$ 66,514,000
Unrealized Gains	914,000	1,442,000
Unrealized Losses	(184,000)	(263,000)
Accrued Interest	81,000	109,000
Estimated Fair Value	52,644,000	67,802,000
Cash & Cash Equivalents	24,459,000	36,382,000	39,937,000	14,262,000
Investment Securities	28,185,000	31,420,000
Cash
Cash and Cash Equivalents and Marketable Securities [Line Items]
Cost	23,894,000	30,958,000
Unrealized Gains	0	0
Unrealized Losses	0	0
Accrued Interest	0	0
Estimated Fair Value	23,894,000	30,958,000
Cash & Cash Equivalents	23,894,000	30,958,000
Investment Securities	0	0
Fair Value, Inputs, Level 1
Cash and Cash Equivalents and Marketable Securities [Line Items]
Cost	19,265,000	24,037,000
Unrealized Gains	807,000	1,265,000
Unrealized Losses	(165,000)	(216,000)
Accrued Interest	15,000	26,000
Estimated Fair Value	19,922,000	25,112,000
Cash & Cash Equivalents	565,000	5,424,000
Investment Securities	19,357,000	19,688,000
Fair Value, Inputs, Level 1 | Money Market Accounts
Cash and Cash Equivalents and Marketable Securities [Line Items]
Cost	565,000	5,424,000
Unrealized Gains	0	0
Unrealized Losses	0	0
Accrued Interest	0	0
Estimated Fair Value	565,000	5,424,000
Cash & Cash Equivalents	565,000	5,424,000
Investment Securities	0	0
Fair Value, Inputs, Level 1 | Mutual Funds
Cash and Cash Equivalents and Marketable Securities [Line Items]
Cost	10,733,000	7,887,000
Unrealized Gains	63,000	127,000
Unrealized Losses	(129,000)	(164,000)
Accrued Interest	0	0
Estimated Fair Value	10,667,000	7,850,000
Cash & Cash Equivalents	0	0
Investment Securities	10,667,000	7,850,000
Fair Value, Inputs, Level 1 | Corporate Equity Securities
Cash and Cash Equivalents and Marketable Securities [Line Items]
Cost	3,408,000	4,614,000
Unrealized Gains	695,000	1,076,000
Unrealized Losses	(31,000)	(9,000)
Accrued Interest	0	0
Estimated Fair Value	4,072,000	5,681,000
Cash & Cash Equivalents	0	0
Investment Securities	4,072,000	5,681,000
Fair Value, Inputs, Level 1 | Government Agency Securities
Cash and Cash Equivalents and Marketable Securities [Line Items]
Cost	4,559,000	6,112,000
Unrealized Gains	49,000	62,000
Unrealized Losses	(5,000)	(43,000)
Accrued Interest	15,000	26,000
Estimated Fair Value	4,618,000	6,157,000
Cash & Cash Equivalents	0	0
Investment Securities	4,618,000	6,157,000
Fair Value, Inputs, Level 2
Cash and Cash Equivalents and Marketable Securities [Line Items]
Cost	8,674,000	11,519,000
Unrealized Gains	107,000	177,000
Unrealized Losses	(19,000)	(47,000)
Accrued Interest	66,000	83,000
Estimated Fair Value	8,828,000	11,732,000
Cash & Cash Equivalents	0	0
Investment Securities	8,828,000	11,732,000
Fair Value, Inputs, Level 2 | Municipal Bonds
Cash and Cash Equivalents and Marketable Securities [Line Items]
Cost	3,652,000	3,524,000
Unrealized Gains	78,000	103,000
Unrealized Losses	(7,000)	0
Accrued Interest	28,000	25,000
Estimated Fair Value	3,751,000	3,652,000
Cash & Cash Equivalents	0	0
Investment Securities	3,751,000	3,652,000
Fair Value, Inputs, Level 2 | Corporate Bonds
Cash and Cash Equivalents and Marketable Securities [Line Items]
Cost	5,022,000	7,995,000
Unrealized Gains	29,000	74,000
Unrealized Losses	(12,000)	(47,000)
Accrued Interest	38,000	58,000
Estimated Fair Value	5,077,000	8,080,000
Cash & Cash Equivalents	0	0
Investment Securities	$ 5,077,000	$ 8,080,000