INCOME TAXES - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Loss Carryforwards [Line Items]
Provisional tax expense	$ 97,900	$ 97,900
Provisional amount related to remeasurement of deferred tax assets and liabilities	96,400
One-time transition tax on mandatory deemed repatriation of foreign earnings	3,100
Undistributed earnings of foreign subsidiaries	20,100	20,100
Reversal of deferred tax liability for unremitted foreign earnings	1,600	$ 1,600
Remeasurement of certain deferred tax assets and liabilities net of reversal	1,500
Effective income tax rate		8.06%	2.52%	1.25%
Increase in effective income tax rate		5.54%
Impact of 2017 Tax Act on effective income tax rate		3.52%	0.00%	0.00%
Impact of increase in fee revenue on effective income tax rate		4.04%
Foreign tax credit carryforward	15,028	$ 15,028	$ 15,028
Valuation allowance	11,872	11,872	9,768
Significant change to tax positions within 12 months	0	0
Unrecognized tax benefits, penalties accrued		100	600
Unrecognized tax benefits, interest accrued		2,200	1,200
Unrecognized tax benefits, liability for penalties	2,300	2,300	2,300
Unrecognized tax benefits, liability for interest	7,900	7,900	$ 5,700
Federal
Operating Loss Carryforwards [Line Items]
Net operating loss carryforward	106,800	106,800
State and Local
Operating Loss Carryforwards [Line Items]
Net operating loss carryforward	$ 14,300	$ 14,300