Marketable Securities - Fair Value Hierarchy of Assets Measured on Recurring Basis (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011
Schedule of Available-for-sale Securities [Line Items]
Total available-for-sale securities	$ 27,228	$ 27,165	$ 26,203
Level 1
Schedule of Available-for-sale Securities [Line Items]
Total available-for-sale securities	27,228	27,165	26,203
Level 2
Schedule of Available-for-sale Securities [Line Items]
Total available-for-sale securities	0	0	0
Level 3
Schedule of Available-for-sale Securities [Line Items]
Total available-for-sale securities	0	0	0
Common stock
Schedule of Available-for-sale Securities [Line Items]
Total available-for-sale securities	360	320	295
Common stock \| Level 1
Schedule of Available-for-sale Securities [Line Items]
Total available-for-sale securities	360	320	295
Common stock \| Level 2
Schedule of Available-for-sale Securities [Line Items]
Total available-for-sale securities	0	0	0
Common stock \| Level 3
Schedule of Available-for-sale Securities [Line Items]
Total available-for-sale securities	0	0	0
Government and agency securities
Schedule of Available-for-sale Securities [Line Items]
Total available-for-sale securities	26,868	26,845	25,908
Government and agency securities \| Level 1
Schedule of Available-for-sale Securities [Line Items]
Total available-for-sale securities	26,868	26,845	25,908
Government and agency securities \| Level 2
Schedule of Available-for-sale Securities [Line Items]
Total available-for-sale securities	0	0	0
Government and agency securities \| Level 3
Schedule of Available-for-sale Securities [Line Items]
Total available-for-sale securities	$ 0	$ 0	$ 0

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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