Marketable Securities (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Available for sale Securities, Debt Maturities [Abstract]
Due within one year	$ 25,880
Due in one to five years	2,879
Total	28,759
Short-Term Marketable Securities:
Marketable Securities [Line Items]
Amortized Cost	25,860	26,829
Gross Unrealized Gains	22	23
Gross Unrealized Losses	2	1
Fair Value	25,880	26,851
Long-Term Marketable Securities:
Marketable Securities [Line Items]
Amortized Cost	2,876	12,493
Gross Unrealized Gains	4	55
Gross Unrealized Losses	1	0
Fair Value	2,879	12,548
U.S. Treasury securities | Short-Term Marketable Securities:
Marketable Securities [Line Items]
Amortized Cost	1,500	1,800
Gross Unrealized Gains	3	5
Gross Unrealized Losses	0	0
Fair Value	1,503	1,805
U.S. Treasury securities | Long-Term Marketable Securities:
Marketable Securities [Line Items]
Amortized Cost		1,502
Gross Unrealized Gains		19
Gross Unrealized Losses		0
Fair Value		1,521
U.S. government and agency securities | Short-Term Marketable Securities:
Marketable Securities [Line Items]
Amortized Cost	151	3,018
Gross Unrealized Gains	1	5
Gross Unrealized Losses	0	0
Fair Value	152	3,023
U.S. government and agency securities | Long-Term Marketable Securities:
Marketable Securities [Line Items]
Amortized Cost		156
Gross Unrealized Gains		2
Gross Unrealized Losses		0
Fair Value		158
Commercial paper and certificates of deposit | Short-Term Marketable Securities:
Marketable Securities [Line Items]
Amortized Cost	1,300	6,001
Gross Unrealized Gains	0	2
Gross Unrealized Losses	0	0
Fair Value	1,300	6,003
Corporate debt securities | Short-Term Marketable Securities:
Marketable Securities [Line Items]
Amortized Cost	22,409	16,010
Gross Unrealized Gains	18	11
Gross Unrealized Losses	2	1
Fair Value	22,425	16,020
Corporate debt securities | Long-Term Marketable Securities:
Marketable Securities [Line Items]
Amortized Cost	2,876	10,835
Gross Unrealized Gains	4	34
Gross Unrealized Losses	1	0
Fair Value	2,879	10,869
Municipal debt securities | Short-Term Marketable Securities:
Marketable Securities [Line Items]
Amortized Cost	500	0
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	$ 500	$ 0