EMPLOYEE BENEFITS - Summary of RSU and Share Transactions (Details) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Restricted Stock Units (RSUs)
Units
Beginning balance (in shares)	782,365
Granted (in shares)	271,144
Shares issued (in shares)	(263,219)
Forfeited (in shares)	(16,127)
Ending balance (in shares)	774,163	782,365
Weighted Average Grant-Date Fair Value
Beginning balance (in dollars per share)	$ 50.25
Granted (in dollars per share)	67.91	$ 56.69	$ 55.97
Shares issued (in dollars per share)	55.34
Forfeited (in dollars per share)	63.31
Ending balance (in dollars per share)	$ 54.43	$ 50.25
Performance Shares
Units
Beginning balance (in shares)	499,564
Granted (in shares)	165,022
Shares issued (in shares)	(162,959)
Forfeited (in shares)	(14,720)
Ending balance (in shares)	486,907	499,564
Weighted Average Grant-Date Fair Value
Beginning balance (in dollars per share)	$ 56.08
Granted (in dollars per share)	68.33	$ 56.77	$ 55.70
Shares issued (in dollars per share)	55.69
Forfeited (in dollars per share)	58.20
Ending balance (in dollars per share)	$ 60.30	$ 56.08