SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Net Loss Per Common Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended									12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013		Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Numerator:
Net income	$ 13,126	$ 4,284	$ 20,422	$ 4,022	$ 57,886	[1]	$ 5,542	$ 15,382	$ (4,758)	$ 41,854	$ 74,052	$ 9,660
Denominator:
Weighted average common shares outstanding - Basic (in shares)										46,252,960	45,898,019	45,951,276
Effect of dilutive shares:
Common stock equivalents arising from stock options and ESPP (in shares)										265,129	458,574	648,661
Restricted stock awards and units (in shares)										167,056	187,012	283,665
Weighted average common shares outstanding - Diluted (in shares)										46,685,145	46,543,605	46,883,602
Net income (loss) per common share:
Basic (in dollars per share)	$ 0.29	$ 0.09	$ 0.44	$ 0.09	$ 1.26		$ 0.12	$ 0.34	$ (0.10)	$ 0.90	$ 1.61	$ 0.21
Diluted (in dollars per share)	$ 0.28	$ 0.09	$ 0.44	$ 0.09	$ 1.24		$ 0.12	$ 0.33	$ (0.10)	$ 0.90	$ 1.59	$ 0.21
Anti-dilutive shares excluded from the calculation of diluted net loss per common share (in shares)										87,894	140,839	212,941
Deferred revenue [Abstract]
License fee agreement, term of agreement (in years)										6 years 4 months 24 days
Taxes, Other										4,300	178	406
Accounts receivable [Abstract]
Unbilled receivables, current	0				92					0	92
Research and Development [Abstract]
Development and operations in the Company’s facilities										27,891	23,491	21,381
PPG OLED Materials Agreement (Note 8)										10,614	7,470	6,170
Costs incurred under sponsored research agreements										2,014	2,671	2,058
Scientific Advisory Board compensation										635	583	423
Research and Development Expense, Total										$ 41,154	$ 34,215	$ 30,032

[1] During the three months ended December 31, 2013, the Company released income tax valuation allowances of $59.4 million.