GOODWILL AND OTHER INTANGIBLE ASSETS - Carrying Amount of Goodwill (Details) - USD ($)	3 Months Ended			6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021
Goodwill [Roll Forward]
Goodwill - net book value, begging of period		$ 1,427,883,000	$ 1,425,542,000	$ 1,428,610,000
Merger purchase accounting adjustments	$ 0	727,000	2,341,000	0
Goodwill - net book value, end of period	$ 1,428,610,000	$ 1,428,610,000	$ 1,427,883,000	$ 1,428,610,000