STOCK-BASED and OTHER COMPENSATION - Options, assumptions (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Restricted Stock and Units [Member]
Options, Restricted Stock and Unit Awards
Unrecognized compensation costs related to unvested awards (in dollars)	$ 85,800
Expected period to recognize unamortized compensation costs related to unvested awards	2 years 2 months 12 days
Restricted Stock Units (RSUs) [Member]
Options, Restricted Stock and Unit Awards
Share Based Compensation Arrangement by Share Based Payment Award, Equity Instruments Other than Options, Outstanding, Number	8,838	8,838
Employee Stock Option [Member]
Options, Restricted Stock and Unit Awards
Unrecognized compensation costs related to unvested awards (in dollars)	$ 3,900
Expected period to recognize unamortized compensation costs related to unvested awards	1 year 9 months 18 days
Outstanding Stock Options
Outstanding balance at beginning of period (in shares)	384,082
Granted (in shares)	69,000	82,500	144,400
Exercised (in shares)	(141,517)	(211,258)	(276,069)
Canceled (in shares)	(666)
Forfeited (in shares)	(11,670)
Outstanding balance at end of period (in shares)	299,229	384,082
Exercisable at end of period (in shares)	142,188
Weighted Average Exercise Price
Outstanding balance at beginning of period (in dollars per share)	$ 78.19
Granted (in dollars per share)	115.28	$ 139.02	$ 72.25
Exercised (in dollars per share)	59.73
Canceled (in dollars per share)	139.02
Forfeited (in dollars per share)	118.77
Outstanding at end of period (in dollars per share)	93.76	$ 78.19
Exercisable at end of period (in dollars per share)	$ 74.07
Weighted Average Remaining Term
Weighted Average Remaining Term, Outstanding at end of period	4 years 10 months 24 days
Weighted Average Remaining Term, Exercisable at end of period	3 years 10 months 24 days
Aggregate Intrinsic Value
Aggregate Intrinsic Value Outstanding at end of period (in dollars)	$ 4,095
Aggregate Intrinsic Value Exercisable at the end of the period (in dollars)	$ 3,398
Grant-Date Fair value
Number of options exercised (in shares)	141,517	211,258	276,069
Cash received from option exercises	$ 8,451	$ 11,898	$ 14,494
Tax benefit from option exercises included in paid-in-capital	4,442
Intrinsic value of stock options exercised	7,467	15,384	10,109
Grant date fair value of options vested	$ 2,734	$ 4,419	$ 2,521
Granted (in dollars per share)	$ 37.56	$ 41.69	$ 21.64
Non-vested Stock Options
Non-vested at the beginning of the period (in shares)	205,156
Granted (in shares)	69,000	82,500	144,400
Vested (in shares)	(105,445)
Forfeited (in shares)	(11,670)
Non-vested at the end of the period (in shares)	157,041	205,156
Weighted Average Grant Date Fair Value - Non-Vested Stock Options
Non-vested as of January (in dollars per share)	$ 29.35
Granted (in dollars per share)	37.56	$ 41.69	$ 21.64
Vested (in dollars per share)	25.93
Forfeited (in dollars per share)	35.89
Non-vested as of December (in dollars per share)	34.77	29.35
Weighted Average Exercise Price - Non-Vested Stock Options
Non-vested at the beginning of the period (in dollars per share)	94.76
Granted (in dollars per share)	115.28
Vested (in dollars per share)	80.49
Forfeited (in dollars per share)	118.77
Non-vested at the end of the period (in dollars per share)	$ 111.58	$ 94.76
Assumptions used to determine the fair market value of options
Granted (in shares)	69,000	82,500	144,400
Weighted average grant-date fair value	$ 37.56	$ 41.69	$ 21.64
Weighted average exercise price	$ 115.28	$ 139.02	$ 72.25
Total fair value of options granted	$ 2,592	$ 3,439	$ 3,125
Expected years until exercise	5 years	4 years	4 years
Expected stock volatility (as a percent)	36.60%	36.70%	38.60%
Dividend yield (as a percent)	0.60%	0.50%	0.80%
Risk-free interest rate (as a percent)	1.60%	1.80%	1.40%
Maximum [Member] | Employee Stock Option [Member]
Grant-Date Fair value
Vesting period	5 years
Term of options from grant to expiration	10 years
Minimum [Member] | Employee Stock Option [Member]
Grant-Date Fair value
Vesting period	3 years
Term of options from grant to expiration	7 years