Summary of Significant Accounting Policies, Summary of Significant Accounting Policies continued (Details) (USD $)	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Assets and liabilities measured at fair value on a recurring basis [Abstract]
Assets measured at fair value on a recurring basis	$ 99,707,000		$ 109,086,000
Losses [Abstract]
Auction rate securities, fair value	1,000,000
Foreign Currencies [Abstract]
Foreign currency transaction loss	40,000		299,000
Foreign currency transaction gain					298,000
Components of accumulated other comprehensive loss [Abstract]
Unrealized loss on marketable securities, net of taxes	(185,661)		(192,861)
Foreign currency translation adjustment	(67,230)		(70,988)
Total accumulated other comprehensive loss	(252,891)		(263,849)
Level 1 [Member]
Assets and liabilities measured at fair value on a recurring basis [Abstract]
Assets measured at fair value on a recurring basis	98,710,000		108,088,000
Level 2 [Member]
Assets and liabilities measured at fair value on a recurring basis [Abstract]
Assets measured at fair value on a recurring basis	0		0
Level 3 [Member]
Assets and liabilities measured at fair value on a recurring basis [Abstract]
Assets measured at fair value on a recurring basis	997,000		998,000
Cash and Cash Equivalents [Member]
Assets and liabilities measured at fair value on a recurring basis [Abstract]
Assets measured at fair value on a recurring basis	55,116,000		63,077,000
Cash and Cash Equivalents [Member] | Level 1 [Member]
Assets and liabilities measured at fair value on a recurring basis [Abstract]
Assets measured at fair value on a recurring basis	55,116,000		63,077,000
Cash and Cash Equivalents [Member] | Level 2 [Member]
Assets and liabilities measured at fair value on a recurring basis [Abstract]
Assets measured at fair value on a recurring basis	0		0
Cash and Cash Equivalents [Member] | Level 3 [Member]
Assets and liabilities measured at fair value on a recurring basis [Abstract]
Assets measured at fair value on a recurring basis	0		0
Short-term Investments [Member]
Assets and liabilities measured at fair value on a recurring basis [Abstract]
Assets measured at fair value on a recurring basis	33,058,000	[1]	24,740,000	[1]
Short-term Investments [Member] | Level 1 [Member]
Assets and liabilities measured at fair value on a recurring basis [Abstract]
Assets measured at fair value on a recurring basis	33,058,000	[1]	24,740,000	[1]
Short-term Investments [Member] | Level 2 [Member]
Assets and liabilities measured at fair value on a recurring basis [Abstract]
Assets measured at fair value on a recurring basis	0	[1]	0	[1]
Short-term Investments [Member] | Level 3 [Member]
Assets and liabilities measured at fair value on a recurring basis [Abstract]
Assets measured at fair value on a recurring basis	0	[1]	0	[1]
Other Investments [Member]
Assets and liabilities measured at fair value on a recurring basis [Abstract]
Assets measured at fair value on a recurring basis	10,536,000	[1]	20,271,000	[1]
Other Investments [Member] | Level 1 [Member]
Assets and liabilities measured at fair value on a recurring basis [Abstract]
Assets measured at fair value on a recurring basis	10,536,000	[1]	20,271,000	[1]
Other Investments [Member] | Level 2 [Member]
Assets and liabilities measured at fair value on a recurring basis [Abstract]
Assets measured at fair value on a recurring basis	0	[1]	0	[1]
Other Investments [Member] | Level 3 [Member]
Assets and liabilities measured at fair value on a recurring basis [Abstract]
Assets measured at fair value on a recurring basis	0	[1]	0	[1]
Auction Rate Municipal Securities [Member]
Assets and liabilities measured at fair value on a recurring basis [Abstract]
Assets measured at fair value on a recurring basis	997,000		998,000
Investment par value	1,300,000		1,300,000
Maturity date	Dec. 31, 2045		Dec. 31, 2045
Summary of change in balance sheet carrying values associated with Level 3 financial instruments [Roll Forward]
Balance at December 31, 2011	998
Net transfers in/(out) of Level 3	0
Purchases	0
Settlements (at par)	0
Gains
Realized	0
Unrealized	0
Losses [Abstract]
Realized	0
Unrealized	(1)
Balance at December 31, 2012	997		998
Auction Rate Municipal Securities [Member] | Level 1 [Member]
Assets and liabilities measured at fair value on a recurring basis [Abstract]
Assets measured at fair value on a recurring basis	0		0
Auction Rate Municipal Securities [Member] | Level 2 [Member]
Assets and liabilities measured at fair value on a recurring basis [Abstract]
Assets measured at fair value on a recurring basis	0		0
Auction Rate Municipal Securities [Member] | Level 3 [Member]
Assets and liabilities measured at fair value on a recurring basis [Abstract]
Assets measured at fair value on a recurring basis	$ 997,000		$ 998,000

[1] The amortized cost of these investments approximates fair market value.