SEGMENT REPORTING - Total Revenues Based on Location of the Customer and Long-Lived Assets by Geographic Regions (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Total revenues
Revenues	$ 4,137,908	$ 4,291,900	$ 4,276,037	$ 3,925,327	$ 3,959,786	$ 3,784,451	$ 3,710,018	$ 3,415,125	$ 16,631,172	$ 14,869,380	$ 13,144,413
Long-lived assets
Total long-lived assets	405,423				442,212				405,423	442,212	444,610
United States
Total revenues
Revenues									14,370,454	12,865,087	11,749,602
Long-lived assets
Total long-lived assets	321,766				335,072				321,766	335,072	348,299
Other locations
Total revenues
Revenues									2,260,718	2,004,293	1,394,811
Long-lived assets
Total long-lived assets	$ 83,657				$ 107,140				$ 83,657	$ 107,140	$ 96,311