Segments and Major Customers (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Financial information of business segments
Revenues	$ 99,134	$ 89,855	$ 291,205	$ 239,038
Segment operating expenses	40,728	39,393	126,787	103,898
Segment reconciling items	(41,396)	(38,646)	(125,730)	(102,022)
Operating income (loss)	17,010	11,816	38,688	33,118
Interest and other income (expense), net	(3,079)	(3,051)	(9,263)	(7,975)
Income (Loss) before income taxes	13,931	8,765	29,425	25,143
MID Segment
Financial information of business segments
Revenues	68,787	63,142	206,784	171,154
Segment operating expenses	21,130	20,060	65,187	44,797
Segment Operating Income (Loss)	47,657	43,082	141,597	126,357
RSD Segment
Financial information of business segments
Revenues	26,312	22,532	72,883	53,040
Segment operating expenses	11,796	12,493	36,409	37,507
Segment Operating Income (Loss)	14,516	10,039	36,474	15,533
Other
Financial information of business segments
Revenues	4,035	4,181	11,538	14,844
Segment operating expenses	7,802	6,840	25,191	21,594
Segment Operating Income (Loss)	(3,767)	(2,659)	(13,653)	(6,750)
Operating Segments [Member]
Financial information of business segments
Segment Operating Income (Loss)	$ 58,406	$ 50,462	$ 164,418	$ 135,140