General (Details 6) - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Short-term and long-term investments
Bank overdrafts	$ 28,500	$ 0
Other-than-temporary unrealized losses	0		$ 0
Realized gains or losses	0	$ 0
Amortized Cost	370,988		267,891
Gross Unrealized Gains	55		9
Gross Unrealized Losses	(238)		(246)
Estimated Fair Value	370,805		267,654
U.S. Government and agency securities
Short-term and long-term investments
Amortized Cost	4,976		4,305
Gross Unrealized Gains	6
Gross Unrealized Losses			(2)
Estimated Fair Value	4,982		4,303
Obligations of government-sponsored enterprises
Short-term and long-term investments
Amortized Cost	43,045		15,318
Gross Unrealized Gains	25		1
Gross Unrealized Losses	(3)		(4)
Estimated Fair Value	43,067		15,315
Corporate debt securities
Short-term and long-term investments
Amortized Cost	321,817		247,118
Gross Unrealized Gains	24		8
Gross Unrealized Losses	(235)		(240)
Estimated Fair Value	321,606		246,886
Certificates of deposit
Short-term and long-term investments
Amortized Cost	1,150		1,150
Estimated Fair Value	$ 1,150		$ 1,150