REVENUE RECOGNITION - Cumulative Effect of Revenue Accounting Changes on the Consolidated Balance Sheet (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Current assets:
Accounts receivable, net	$ 1,530,321	$ 1,423,125	$ 1,217,801
Current liabilities:
Accounts payable	841,274	839,167	667,523
Accrued expenses and other current liabilities	1,238,815	1,183,354	1,138,980
Deferred merchant bookings	1,425,649	778,808	980,455
Deferred income taxes	481,220	483,553	481,139
Stockholders' equity:
Retained earnings	14,975,706	14,127,408	13,938,869
Cumulative effect of adoption of accounting standard updates	188,539
Adjustments | Accounting Standards Update 2014-09
Current assets:
Accounts receivable, net	(152,477)	205,324
Current liabilities:
Accounts payable	(104,172)	171,644
Accrued expenses and other current liabilities	(8,897)	44,374
Deferred merchant bookings	117,367	(201,647)
Deferred income taxes	(984)	2,414
Stockholders' equity:
Retained earnings	(133,224)	$ 188,539
As Adjusted (Previous Revenue Standard) [Member]
Current assets:
Accounts receivable, net	1,377,844		1,217,801
Current liabilities:
Accounts payable	737,102		667,523
Accrued expenses and other current liabilities	1,229,918		1,138,980
Deferred merchant bookings	1,543,016		980,455
Deferred income taxes	480,236		481,139
Stockholders' equity:
Retained earnings	14,842,482		$ 13,938,869
Retained Earnings
Stockholders' equity:
Cumulative effect of adoption of accounting standard updates	$ 429,627