Investments - Additional Information (Detail) (USD $)	Jun. 30, 2013	Dec. 31, 2012
Schedule of Trading Securities and Other Trading Assets [Line Items]
Short-term investments	$ 17,940,000	$ 24,361,000
Time deposits of cash and cash equivalents	6,500,000	7,900,000
US Treasury securities and agency [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Short-term investments	1,500,000
FDIC Guaranteed certificates of deposit [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Short-term investments	8,300,000
Corporate Notes and Bonds [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Short-term investments	5,100,000
Commercial Paper [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Short-term investments	998,000
Common stock [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Short-term investments	$ 2,000,000

- Definition

Any certificate of deposit or savings account held by a bank or other financial institution for a short-term specified period of time. Because of their short-term, time deposits are considered highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three-years ago does not become a cash equivalent when its remaining maturity is three months.

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