General (Details 6) (USD $) In Thousands, unless otherwise specified	9 Months Ended		12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Short-term and long-term investments
Other-than-temporary unrealized losses	$ 0		$ 0
Realized gains or losses	(40)	0
Amortized Cost	201,575		208,468
Gross Unrealized Gains	29		20
Gross Unrealized Losses	(180)		(175)
Estimated Fair Value	201,424		208,313
U.S. Government and agency securities
Short-term and long-term investments
Amortized Cost	2,394		1,129
Gross Unrealized Losses	(1)
Estimated Fair Value	2,393		1,129
Obligations of government-sponsored enterprises
Short-term and long-term investments
Amortized Cost	15,222		8,441
Gross Unrealized Gains	2		2
Gross Unrealized Losses	(2)		(3)
Estimated Fair Value	15,222		8,440
Corporate debt securities
Short-term and long-term investments
Amortized Cost	182,809		198,748
Gross Unrealized Gains	27		18
Gross Unrealized Losses	(177)		(172)
Estimated Fair Value	182,659		198,594
Certificates of deposit
Short-term and long-term investments
Amortized Cost	1,150		150
Estimated Fair Value	$ 1,150		$ 150