CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balances at beginning of period at Dec. 31, 2015	$ (329,572)	$ 423	$ 1,055,838	$ (1,319,318)	$ (58,336)	$ (8,179)
Balances at beginning of period (in shares) at Dec. 31, 2015		42,339			(2,809)
Cumulative-effect adjustment due to adoption of ASU No. 2016-09	0		49	(49)
Stock issued pursuant to employee stock plans	5,243		(20,740)		$ 25,983
Stock issued pursuant to employee stock plans (in shares)					1,197
Stock-based compensation	7,916		7,916
Net (loss) income	48,219			48,219
Other comprehensive income (loss)	(1,717)					(1,717)
Balances at end of period at Dec. 31, 2016	(269,911)	$ 423	1,043,063	(1,271,148)	$ (32,353)	(9,896)
Balances at end of period (in shares) at Dec. 31, 2016		42,339			(1,612)
Stock issued pursuant to employee stock plans	(884)		(15,565)		$ 14,681
Stock issued pursuant to employee stock plans (in shares)					629
Stock-based compensation	8,311		8,311
Net (loss) income	(13,555)			(13,555)
Other comprehensive income (loss)	7,470					7,470
Partial retirement of convertible senior notes conversion feature	(5)		(5)
Partial unwind capped call cash receipt	4		4
Balances at end of period at Dec. 31, 2017	$ (268,570)	$ 423	1,035,808	(1,284,703)	$ (17,672)	(2,426)
Balances at end of period (in shares) at Dec. 31, 2017	41,356	42,339			(983)
Cumulative-effect adjustment due to adoption of ASU No. 2016-09	$ 108,367			108,367
Stock issued pursuant to employee stock plans	(643)		(13,084)		$ 12,441
Stock issued pursuant to employee stock plans (in shares)					592
Stock-based compensation	6,258		6,258
Net (loss) income	(10,674)			(10,674)
Other comprehensive income (loss)	(1,341)					(1,341)
Partial retirement of convertible senior notes conversion feature	(74)		(74)
Partial unwind capped call cash receipt	16		16
Balances at end of period at Dec. 31, 2018	$ (166,661)	$ 423	$ 1,028,924	$ (1,187,010)	$ (5,231)	$ (3,767)
Balances at end of period (in shares) at Dec. 31, 2018	41,948	42,339			(391)