Summary of Fair Value and Duration of Investments, Including Cash Equivalents, that have been Classified in Gross Unrealized Loss Position (Detail) (USD $)	Sep. 30, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months Fair Value	$ 7,015,000	$ 27,504,000
Less than 12 Months Unrealized Losses	(12,000)	(164,000)
More than 12 Months Fair Value	425,000	1,007,000
More than 12 Months Unrealized Losses	(9,000)	(9,000)
TOTAL Fair Value	7,440	28,511
TOTAL Unrealized Losses	(21)	(173)
Foreign government securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months Fair Value	2,001,000	3,778,000
Less than 12 Months Unrealized Losses	(1,000)	(4,000)
TOTAL Fair Value	2,001	3,778
TOTAL Unrealized Losses	(1)	(4)
Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months Fair Value	2,666,000	16,708,000
Less than 12 Months Unrealized Losses	(2,000)	(108,000)
More than 12 Months Fair Value		1,006,000
More than 12 Months Unrealized Losses		(9,000)
TOTAL Fair Value	2,666	17,714
TOTAL Unrealized Losses	(2)	(117)
Mortgage-backed securities - residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months Fair Value	2,348,000	3,508,000
Less than 12 Months Unrealized Losses	(9,000)	(42,000)
More than 12 Months Fair Value	425,000	1,000
More than 12 Months Unrealized Losses	(9,000)
TOTAL Fair Value	2,773	3,509
TOTAL Unrealized Losses	(18)	(42)
U.S. Government and securities and sponsored entities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months Fair Value		3,510,000
Less than 12 Months Unrealized Losses		(10,000)
TOTAL Fair Value		3,510
TOTAL Unrealized Losses		$ (10)