CONSOLIDATED STATEMENT OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]	Treasury Stock [Member]	Series A Nonconvertible Preferred Stock [Member] Preferred Stock [Member]
BALANCE at Dec. 31, 2015					$ (9,819)
Net income	$ 1,949
Other comprehensive income	(703)
BALANCE at Mar. 31, 2016					(10,522)
BALANCE (in shares) at Dec. 31, 2016		48,270,990				1,357,863	200,000
BALANCE at Dec. 31, 2016	528,468	$ 483	$ 604,364	$ (25,557)	(10,666)	$ (40,158)	$ 2
Cumulative effect of recording excess tax benefits from share-based payment arrangements	26,450			26,450
Net income	10,365			10,365
Cash dividend	(1,414)			(1,414)
Other comprehensive income	314				314
Exercise of common stock options (in shares)		1,500
Exercise of common stock options	24		24
Issuance of common stock to employees (in shares)		114,038
Issuance of common stock to employees	3,273	$ 1	3,272
Shares withheld for employee taxes (in shares)		(42,277)
Shares withheld for employee taxes	(3,541)		(3,541)
Issuance of common stock to Board of Directors and Scientific Advisory Board (in shares)		17,314
Issuance of common stock to Board of Directors and Scientific Advisory Board	1,009		1,009
Issuance of common stock to employees under an ESPP (in shares)		3,330
Issuance of common stock to employees under an ESPP	203		203
BALANCE (in shares) at Mar. 31, 2017		48,364,895				1,357,863	200,000
BALANCE at Mar. 31, 2017	$ 565,151	$ 484	$ 605,331	$ 9,844	$ (10,352)	$ (40,158)	$ 2