Significant Accounting Policies, Cash, Cash Equivalents and Investments (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Cash and Cash Equivalents and Investments [Line Items]
Amortized cost	$ 75,557	$ 72,373
Gross unrealized gains	7	8
Gross unrealized losses	(15)	(24)
Fair value disclosure	75,549	72,357
Cash [Member]
Cash and Cash Equivalents and Investments [Line Items]
Amortized cost	18,527	15,660
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Fair value disclosure	18,527	15,660
Money Market Funds [Member]
Cash and Cash Equivalents and Investments [Line Items]
Amortized cost	12,362	11,771
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Fair value disclosure	12,362	11,771
Certificates of Deposit [Member]
Cash and Cash Equivalents and Investments [Line Items]
Amortized cost	4,080	4,258
Gross unrealized gains	0	0
Gross unrealized losses	(2)	(2)
Fair value disclosure	4,078	4,256
Commercial Paper [Member]
Cash and Cash Equivalents and Investments [Line Items]
Amortized cost	11,297	7,298
Gross unrealized gains	0	0
Gross unrealized losses	(2)	0
Fair value disclosure	11,295	7,298
Corporate notes and bonds [Member]
Cash and Cash Equivalents and Investments [Line Items]
Amortized cost	29,291	33,386
Gross unrealized gains	7	8
Gross unrealized losses	(11)	(22)
Fair value disclosure	29,287	33,372
Cash and cash equivalents [Member]
Cash and Cash Equivalents and Investments [Line Items]
Amortized cost	31,609	28,390
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Fair value disclosure	31,609	28,390
Short-term investments [Member]
Cash and Cash Equivalents and Investments [Line Items]
Amortized cost	43,948	43,983
Gross unrealized gains	7	8
Gross unrealized losses	(15)	(24)
Fair value disclosure	$ 43,940	$ 43,967