SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Narrative (Detail) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		12 Months Ended
	Jun. 30, 2016 segment	Mar. 31, 2016 segment	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 USD ($) shares	Jan. 01, 2019 USD ($)	Jan. 01, 2018 USD ($)	Dec. 31, 2015 USD ($)
Immaterial Error Corrections [Abstract]
Stockholders' equity			$ 290,230	$ 307,518	$ 231,880			$ 251,282
Inventories
Inventory reserves			1,100	900
Long-lived Assets (Excluding Goodwill and Intangibles)
Impairment of assets-held-for-sale			2,600
Goodwill
Impairment of goodwill			0	0	6,980
Research and Development
Research and development costs			$ 1,800	$ 3,700	$ 4,600
Earnings (Loss) per Share
Anti-dilutive share-based awards, excluded (in shares) | shares			3,647	2,543	2,499
Segment Reporting
Number of operating segments | segment	1	2
Recent Accounting Pronouncements
Accumulated deficit			$ (138,709)	$ (115,433)	$ (102,044)		$ (116,429)
Deferred income taxes, noncurrent			$ 13,955	$ 19,367	30,404		19,042
Accounting Standards Update 2014-09 | Adjustments
Recent Accounting Pronouncements
Accumulated deficit							(996)
Deferred income taxes, noncurrent							$ (325)
Accounting Standards Update 2015-17
Recent Accounting Pronouncements
Deferred income taxes, current					1,200
Deferred income taxes, noncurrent					$ (1,200)
Convertible Notes
Earnings (Loss) per Share
Anti-dilutive share-based awards, excluded (in shares) | shares			1,500	10,100	10,100
Convertible Senior Notes | Convertible Notes
Earnings (Loss) per Share
Debt instrument, conversion ratio | $ / shares			$ 14.83
Continuing Operations
Goodwill
Impairment of goodwill			$ 0	$ 0	$ 0
Minimum
Property and Equipment
Estimated useful lives of property and equipment			3 years
Intangibles
Estimated useful lives of intangible assets			1 year
Concentrations of Credit Risk
Percentage of contracts issued by US Government			90.00%
Income Taxes
Recognition of tax liability or benefits			50.00%
Maximum
Property and Equipment
Estimated useful lives of property and equipment			7 years
Intangibles
Estimated useful lives of intangible assets			16 years
Adjustment
Immaterial Error Corrections [Abstract]
Stockholders' equity				(3,494)	(1,056)
Recent Accounting Pronouncements
Accumulated deficit				(3,494)	(1,056)
Deferred income taxes, noncurrent				193	(5)
Forecast | Accounting Standards Update 2016-02
Recent Accounting Pronouncements
Right-of-use assets						$ 28,000
Lease liabilities						$ 38,000
Retained Earnings
Immaterial Error Corrections [Abstract]
Stockholders' equity			$ (138,709)	(115,433)	$ (102,044)			$ (75,803)
Retained Earnings | Adjustment
Immaterial Error Corrections [Abstract]
Stockholders' equity				$ 3,500