STOCK-BASED COMPENSATION PLANS - Summary of fully vested and exercisable stock options and stock options expected to vest (Details 2) (Stock Option, USD $) Share data in Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fully Vested and Exercisable, Total shares	2,532
Fully Vested and Exercisable, Weighted-average exercise price	$ 6.31
Fully Vested and Exercisable, Aggregate intrinsic value	$ 4,921,295
Fully Vested and Exercisable, Weighted-average remaining contractual term (in years)	6 years
Expected to Vest, Total shares	4,376
Expected to Vest, Weighted-average exercise price	$ 6.52
Expected to Vest, Aggregate intrinsic value	$ 5,917,234
Expected to Vest, Weighted-average remaining contractual term (in years)	7 years 1 month 6 days