BUSINESS COMBINATIONS - Purchase Price Allocation (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Oct. 03, 2016
Preliminary Recording of Assets Acquired and Liabilities Assumed
Goodwill	$ 184,932	$ 184,557
Creehan Holding Co., Inc.
Preliminary Recording of Assets Acquired and Liabilities Assumed
Cash and cash equivalents			$ 861
Accounts receivable			9,048
Other current assets			171
Property, equipment and capitalized software			641
Intangible assets			50,900
Goodwill	$ 184,932	$ 184,557	51,362
Total assets acquired			112,983
Current liabilities			(916)
Deferred revenue			(1,900)
Total liabilities assumed			(2,816)
Net assets acquired			$ 110,167