ACQUISITIONS - Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	May 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Goodwill		$ 266,345	$ 261,705	$ 58,327
Weebly, Inc
Business Acquisition [Line Items]
Cash	$ 132,432
Stock (2,418,271 shares of Class A common stock)	$ 140,107
Equity consideration (in shares)	2,418,271
Consideration	$ 272,539
Current assets (inclusive of cash acquired of $25,758)	46,978
Cash acquired	25,758
Total liabilities assumed (including deferred revenue of $22,800)	(37,509)
Deferred revenue	22,800
Total identifiable net assets acquired	79,330
Goodwill	193,209
Total	272,539
Intangible customer assets | Weebly, Inc
Business Acquisition [Line Items]
Intangible assets	42,700
Intangible technology assets | Weebly, Inc
Business Acquisition [Line Items]
Intangible assets	14,900
Intangible trade name | Weebly, Inc
Business Acquisition [Line Items]
Intangible assets	11,300
Intangible other assets | Weebly, Inc
Business Acquisition [Line Items]
Intangible assets	$ 961