Amortized Cost and Fair Market Value of Available for Sale Investments (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 90,353	$ 67,702
Gross Unrealized Gains	1,206	931
Gross Unrealized Losses	35	145
Fair Market Value	91,524	68,488
Money market investments
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,094	1,989
Fair Market Value	1,094	1,989
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,833	3,017
Gross Unrealized Gains	89	61
Gross Unrealized Losses	1	18
Fair Market Value	2,921	3,060
Corporate bonds and direct obligations of government agencies
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	73,427	51,014
Gross Unrealized Gains	1,070	819
Gross Unrealized Losses	32	126
Fair Market Value	74,465	51,707
U.S. Treasury Obligations
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	12,999	11,682
Gross Unrealized Gains	47	51
Gross Unrealized Losses	2	1
Fair Market Value	$ 13,044	$ 11,732

Amount of debt securities categorized neither as held-to-maturity nor trading.

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+ Details

- Definition

This item represents the gross unrealized gains for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

+ References+ Details