INCOME TAXES - General (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income (loss) before income taxes
United States	$ (6,331)	$ (20,892)	$ 12,273
Foreign	13,993	15,040	4,832
Total	7,662	(5,852)	17,105
Current:
Federal	(8,459)	(6,735)	9,121
State	(187)	(362)	1,849
Foreign	2,700	3,120	1,542
Total	(5,946)	(3,977)	12,512
Deferred:
Federal	14,006	2,599	(4,687)
State	11,103	(3,270)	(1,724)
Foreign	437	133	(106)
Total	25,546	(538)	(6,517)
Total income tax expense (benefit)	19,600	(4,515)	5,995
Reconciliation of the provision for income taxes at the statutory rate to the provision for income taxes at effective rate
Income (loss) before income taxes	7,662	(5,852)	17,105
Consolidated income tax expense (benefit)	$ 19,600	$ (4,515)	$ 5,995
Summary effective tax rate, domestic	35.00%	35.00%	35.00%
Summary effective tax rate, consolidated	255.80%	77.20%	35.00%
Income tax expense (benefit) at the statutory rate	$ 2,682	$ (2,048)	$ 5,987
Valuation allowances	16,794	1,095	707
State income taxes, net of federal tax effect	654	(2,796)	(85)
Foreign income taxes	(1,593)	(2,253)	(863)
Permanent differences	1,335	1,189	797
Uncertain tax positions	(133)	(112)	447
Research and development credits	(770)	(513)	(676)
Nondeductible compensation	(20)	411
Share-based compensation	491	469
Domestic production activities deduction		(5)	(422)
Other	160	48	103
Deferred tax assets:
U.S. net operating loss carryforwards	15,175	2,305
Foreign net operating loss carryforwards	767	831
Income tax credit carryforwards	2,969	1,274
Share-based compensation	5,068	6,206
Intangible assets	2,109	11,747
Deferred rent	812	426
Accrued liabilities	10,211	4,765
Cash flow hedges	1,600	1,067
Allowance for doubtful accounts	646	1,379
Other	658	195
Valuation allowances	(19,230)	(1,903)
Total deferred tax assets	20,785	28,292
Deferred tax liabilities:
Prepaid expenses	(3,837)	(1,875)
Goodwill	(47,343)	(42,994)
Property and equipment and software development costs	(15,216)	(11,324)
Deferred debt discharge income	(1,336)	(1,985)
Total deferred tax liabilities	(67,732)	(58,178)
Net deferred tax liability	$ (46,947)	(29,886)
United Kingdom
Reconciliation of the provision for income taxes at the statutory rate to the provision for income taxes at effective rate
Effective tax rate	21.00%
United States.
Deferred:
Total income tax expense (benefit)	$ 16,463	(7,768)	4,559
Reconciliation of the provision for income taxes at the statutory rate to the provision for income taxes at effective rate
Consolidated income tax expense (benefit)	$ 16,463	$ (7,768)	$ 4,559
Effective tax rate	41.00%
Summary effective tax rate, domestic	(260.00%)	37.20%	37.10%
Foreign
Deferred:
Total income tax expense (benefit)	$ 3,137	$ 3,253	$ 1,436
Reconciliation of the provision for income taxes at the statutory rate to the provision for income taxes at effective rate
Consolidated income tax expense (benefit)	$ 3,137	$ 3,253	$ 1,436
Summary effective tax rate, foreign	22.40%	21.60%	29.70%