STOCK-BASED COMPENSATION - Summary of Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Weighted-Average Grant-Date Fair Value
Proceeds from stock option exercises	$ 68,555	$ 90,834	$ 88,156
Stock options
STOCK-BASED COMPENSATION
Award vesting period (in years)	3 years
Weighted-Average Grant-Date Fair Value
Actual tax benefit realized for the tax deduction from option exercises	$ 14,500
Unrecognized compensation cost expected to be recognized in future periods	$ 200
Weighted-average period over which compensation cost is expected to be recognized (in years)	2 months 12 days
Expiration period (in years)	10 years
Proceeds from stock option exercises	$ 68,600
Restricted stock units
Weighted-Average Grant-Date Fair Value
Actual tax benefit realized for the tax deduction from option exercises	5,800
Unrecognized compensation cost expected to be recognized in future periods	$ 43,300
Weighted-average period over which compensation cost is expected to be recognized (in years)	1 year 7 months 6 days
Restricted stock units (time-based)
Restricted stock unit activity
Balance at the beginning of the period (in shares)	480,729
Granted (in shares)	241,812
Vested (in shares)	(138,606)
Forfeited (in shares)	(7,737)
Balance at the end of the period (in shares)	576,198	480,729
Weighted-Average Grant-Date Fair Value
Nonvested at the beginning of the period (in dollars per share)	$ 95.45
Granted (in dollars per share)	87.13
Vested (in dollars per share)	86.84
Forfeited (in dollars per share)	97.80
Nonvested at the end of the period (in dollars per share)	$ 92.47	$ 95.45
Restricted stock units (performance-based)
Restricted stock unit activity
Balance at the beginning of the period (in shares)	181,680
Granted (in shares)	417,313
Vested (in shares)	0
Forfeited (in shares)	(8,929)
Balance at the end of the period (in shares)	590,064	181,680
Weighted-Average Grant-Date Fair Value
Nonvested at the beginning of the period (in dollars per share)	$ 117.26
Granted (in dollars per share)	93.08
Vested (in dollars per share)	0
Forfeited (in dollars per share)	111.60
Nonvested at the end of the period (in dollars per share)	$ 100.27	$ 117.26
Stock Awards Plans | Stock options
Assumptions used to estimate fair value of restricted stock units granted
Expected stock price volatility			14.20%
Risk-free interest rate			2.80%
Dividend yield			1.50%
Weighted-Average Grant-Date Fair Value
Weighted-average fair value of stock options granted (in dollars per share)			$ 14.82
Assumptions used to estimate fair value of stock options granted
Dividend yield			1.50%
Expected stock price volatility			14.20%
Risk-free interest rate			2.80%
Expected life of option			6 years 7 months 6 days
Stock options activity
Outstanding at the beginning of the period (in shares)	5,044,180
Granted (in shares)	0
Exercised (in shares)	(1,035,649)
Forfeited or expired (in shares)	(10,484)
Outstanding at the end of the period (in shares)	3,998,047	5,044,180
Exercisable at the end of the period (in shares)	3,845,344
Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$ 68.32
Granted (in dollars per share)	0
Exercised (in dollars per share)	60.81
Forfeited or expired (in dollars per share)	80.13
Outstanding at the end of the period (in dollars per share)	70.28	$ 68.32
Exercisable at the end of the period (in dollars per share)	$ 69.45
Weighted-Average Remaining Contractual Term (Years):
Outstanding at the end of the period	4 years 9 months 18 days
Exercisable at the end of the period	4 years 7 months 6 days
Aggregate Intrinsic Value:
Outstanding at the end of the period	$ 256,760
Exercisable at the end of the period	249,299
Intrinsic value of options exercised	$ 59,179	$ 87,251	$ 72,951
Stock Awards Plans | Restricted stock units (time-based)
STOCK-BASED COMPENSATION
Award vesting period (in years)	3 years
Stock Awards Plans | Restricted stock units (performance-based)
STOCK-BASED COMPENSATION
Award vesting period (in years)	3 years
Assumptions used to estimate fair value of restricted stock units granted
Fair value per stock award (in dollars per share)	$ 94.98	$ 134.97	$ 128.70
Grant date stock price (in dollars per share)	$ 83.93	$ 104.51	$ 89.42
Expected stock price volatility	23.80%	16.50%	12.30%
Expected average volatility of peer companies	48.50%	31.90%	27.50%
Correlation assumption	63.50%	37.40%	20.20%
Risk-free interest rate	0.31%	2.19%	2.42%
Dividend yield	1.72%	1.30%	1.43%
Assumptions used to estimate fair value of stock options granted
Dividend yield	1.72%	1.30%	1.43%
Expected stock price volatility	23.80%	16.50%	12.30%
Risk-free interest rate	0.31%	2.19%	2.42%
Director Stock Option Plans | Stock options
Stock options activity
Outstanding at the beginning of the period (in shares)	135,251
Granted (in shares)	0
Exercised (in shares)	(36,051)
Forfeited or expired (in shares)	0
Outstanding at the end of the period (in shares)	99,200	135,251
Exercisable at the end of the period (in shares)	99,200
Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$ 58.45
Granted (in dollars per share)	0
Exercised (in dollars per share)	52.00
Forfeited or expired (in dollars per share)	0
Outstanding at the end of the period (in dollars per share)	60.80	$ 58.45
Exercisable at the end of the period (in dollars per share)	$ 60.80
Weighted-Average Remaining Contractual Term (Years):
Outstanding at the end of the period	2 years 7 months 6 days
Exercisable at the end of the period	2 years 7 months 6 days
Aggregate Intrinsic Value:
Outstanding at the end of the period	$ 7,311
Exercisable at the end of the period	7,311
Intrinsic value of options exercised	$ 2,318	$ 1,172	$ 2,286
Director Stock Option Plans | Restricted stock units
STOCK-BASED COMPENSATION
Award vesting period (in years)	1 year
Director Stock Option Plans | Restricted stock units (time-based)
Restricted stock unit activity
Granted (in shares)	12,379
Vested (in shares)	(11,490)