INCOME TAXES - Unrecognized tax benefits (Details) |
12 Months Ended | ||
|---|---|---|---|
|
Dec. 31, 2015
USD ($)
item
|
Dec. 31, 2014
USD ($)
|
Dec. 31, 2013
USD ($)
|
|
| Reconciliation of the change in the amount of unrecognized tax benefits | |||
| Balance at beginning of period | $ 30,500,000 | $ 27,400,000 | $ 21,900,000 |
| Gross increases-current period tax positions | 1,700,000 | 1,600,000 | 3,800,000 |
| Gross increases-prior periods tax position | 1,100,000 | 1,500,000 | 2,200,000 |
| Favorable resolutions with authorities | (2,200,000) | (500,000) | |
| Lapse of statute of limitations | (1,000,000) | ||
| Balance at end of period | 30,100,000 | $ 30,500,000 | $ 27,400,000 |
| Gross decreases-tax position in prior periods | 800,000 | ||
| Interest expense recognized | $ 1,000,000 | ||
| Number of subsidiaries files income tax returns in the U.S. federal jurisdiction, and various state and foreign jurisdictions | item | 1 | ||