Investments (Details) (USD $) In Thousands, unless otherwise specified	1 Months Ended	12 Months Ended
	Jan. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		$ 12,981	$ 32,515
Gross Unrealized Gains		616	430
Gross Unrealized Losses
Fair Value		13,597	32,945
Auction Rate Security [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		1,175	1,175
Gross Unrealized Gains		615	409
Gross Unrealized Losses
Fair Value		1,790	1,584
Sale proceeds	1,800		3,100
Realized gains	600		900
Gain resulted from reclassification adjustments out of accumulated other comprehensive income			300
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		11,806	31,340
Gross Unrealized Gains		1	21
Gross Unrealized Losses
Fair Value		$ 11,807	$ 31,361