DEBT (Outstanding Debt) (Details) $ / shares in Units, $ in Thousands, € in Millions			1 Months Ended			3 Months Ended			9 Months Ended		12 Months Ended
	Mar. 31, 2016 USD ($)	Aug. 20, 2014 USD ($) Days $ / shares	Nov. 03, 2017 USD ($)	May 31, 2013 USD ($) Days $ / shares	Mar. 31, 2012 USD ($) Days $ / shares	Sep. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) shares	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Sep. 30, 2017 EUR (€)	Aug. 15, 2017 USD ($)	Jul. 24, 2017 USD ($)	Mar. 10, 2017 EUR (€)	Dec. 31, 2016 EUR (€)	May 23, 2016 USD ($)	Nov. 25, 2015 EUR (€)	Mar. 13, 2015 USD ($)	Mar. 03, 2015 EUR (€)	Sep. 23, 2014 EUR (€)	Jun. 30, 2013 USD ($)
Debt Instrument
Outstanding Principal Amount						$ 8,933,250			$ 8,933,250		$ 6,400,563
Unamortized Debt Discount and Debt Issuance Cost						(206,571)			(206,571)		(230,041)
Total Carrying Value of Long-Term Debt						8,726,679			8,726,679		6,170,522
Description of Senior Notes
Convertible debt						9,401			9,401		28,538
Payments Related to Conversion of Senior Notes									89,575	$ 0
Gain (Loss) on Extinguishment of Debt									(1,093)	0
Amortization of debt discount included in interest expense									52,909	51,512
Write off of Deferred Debt Issuance Cost						200			200
1.0% Convertible Senior Notes due March 2018
Debt Instrument
Short-term debt, gross						910,438			910,438		1,000,000
Unamortized Debt Discount and Debt Issuance Cost						(10,636)			(10,636)		(32,266)
Short-term Debt						899,802			899,802		967,734
Description of Senior Notes
Convertible debt						$ 9,400			9,400		$ 28,500
Payments Related to Conversion of Senior Notes									$ 89,600
Stock Issued During Period, Shares, Conversion of Convertible Securities | shares									46,437
Gain (Loss) on Extinguishment of Debt									$ 1,100
Extinguishment of Debt, Gain (Loss), Net of Tax									$ 700
Aggregate principal amount					$ 1,000,000
Interest rate on Long-term Debt					1.00%	1.00%			1.00%		1.00%					1.00%				1.00%
Debt financing costs paid															$ 20,900
Convertible debt conversion price (in dollars per share) | $ / shares					$ 944.61
Ratio of closing share price to conversion price as a condition for conversion of the convertible notes, minimum					150.00%
Effective interest rate at debt origination or modification					3.50%
Debt discount related to convertible notes, net of tax					$ 80,900
Debt discount related to convertible notes, before tax					135,200
Convertible carrying amount of equity component related to finance costs net of tax					$ 2,800
0.35% Convertible Senior Notes due June 2020
Debt Instrument
Outstanding Principal Amount						$ 1,000,000			$ 1,000,000		$ 1,000,000
Unamortized Debt Discount and Debt Issuance Cost						(71,257)			(71,257)		(90,251)
Total Carrying Value of Long-Term Debt						$ 928,743			$ 928,743		$ 909,749
Description of Senior Notes
Aggregate principal amount				$ 1,000,000
Interest rate on Long-term Debt				0.35%		0.35%			0.35%		0.35%					0.35%				0.35%
Debt financing costs paid														$ 1,000
Convertible debt conversion price (in dollars per share) | $ / shares				$ 1,315.10
Ratio of closing share price to conversion price as a condition for conversion of the convertible notes, minimum				150.00%
Unamortized debt discount				$ 20,000
Effective interest rate at debt origination or modification				3.13%
Debt discount related to convertible notes, net of tax																										$ 92,400
Debt discount related to convertible notes, before tax																										154,300
Convertible carrying amount of equity component related to finance costs net of tax																										$ 100
Amortization of debt discount included in interest expense						$ 800		$ 700	$ 2,200	2,100
0.9% Convertible Senior Notes due September 2021
Debt Instrument
Outstanding Principal Amount						1,000,000			1,000,000		$ 1,000,000
Unamortized Debt Discount and Debt Issuance Cost						(88,664)			(88,664)		(104,592)
Total Carrying Value of Long-Term Debt						$ 911,336			$ 911,336		$ 895,408
Description of Senior Notes
Aggregate principal amount		$ 1,000,000
Interest rate on Long-term Debt		0.90%				0.90%			0.90%		0.90%					0.90%				0.90%
Debt financing costs paid													$ 11,000
Convertible debt conversion price (in dollars per share) | $ / shares		$ 2,055.50
Ratio of closing share price to conversion price as a condition for conversion of the convertible notes, minimum		150.00%
Effective interest rate at debt origination or modification		3.18%
Debt discount related to convertible notes, net of tax													82,500
Debt discount related to convertible notes, before tax													142,900
Convertible carrying amount of equity component related to finance costs net of tax													1,600
0.8% (€1 Billion) Senior Notes due March 2022
Debt Instrument
Outstanding Principal Amount						$ 1,182,200			$ 1,182,200
Unamortized Debt Discount and Debt Issuance Cost						(6,574)			(6,574)
Total Carrying Value of Long-Term Debt						$ 1,175,626			$ 1,175,626
Description of Senior Notes
Aggregate principal amount | €																€ 1,000.0			€ 1,000.0
Interest rate on Long-term Debt						0.80%			0.80%							0.80%			0.80%
Debt financing costs paid									$ 5,000
Unamortized debt discount | €																			€ 2.1
Effective interest rate at debt origination or modification																			0.84%
2.15% (€750 Million) Senior Notes due November 2022
Debt Instrument
Outstanding Principal Amount						$ 886,650			886,650		$ 791,063
Unamortized Debt Discount and Debt Issuance Cost						(4,885)			(4,885)		(5,336)
Total Carrying Value of Long-Term Debt						$ 881,765			$ 881,765		$ 785,727
Description of Senior Notes
Aggregate principal amount | €																€ 750.0				€ 750.0		€ 750.0
Interest rate on Long-term Debt						2.15%			2.15%		2.15%					2.15%				2.15%		2.15%
Debt financing costs paid												$ 3,700
Unamortized debt discount | €																						€ 2.2
Effective interest rate at debt origination or modification																						2.20%
2.75% Senior Notes due March 2023
Debt Instrument
Outstanding Principal Amount						$ 500,000			$ 500,000
Unamortized Debt Discount and Debt Issuance Cost						(3,364)			(3,364)
Total Carrying Value of Long-Term Debt						$ 496,636			$ 496,636
Description of Senior Notes
Aggregate principal amount																	$ 500,000
Interest rate on Long-term Debt						2.75%			2.75%							2.75%	2.75%
Debt financing costs paid						$ 2,600
Unamortized debt discount																	$ 700
Effective interest rate at debt origination or modification																	2.78%
2.375% (€1 Billion) Senior Notes due September 2024
Debt Instrument
Outstanding Principal Amount						1,182,200			$ 1,182,200		$ 1,054,750
Unamortized Debt Discount and Debt Issuance Cost						(12,544)			(12,544)		(12,861)
Total Carrying Value of Long-Term Debt						$ 1,169,656			$ 1,169,656		$ 1,041,889
Description of Senior Notes
Aggregate principal amount | €																€ 1,000.0				€ 1,000.0					€ 1,000.0
Interest rate on Long-term Debt						2.375%			2.375%		2.375%					2.375%				2.375%					2.375%
Debt financing costs paid													$ 6,500
Unamortized debt discount | €																									€ 9.4
Effective interest rate at debt origination or modification																									2.48%
3.65% Senior Notes due March 2025
Debt Instrument
Outstanding Principal Amount						$ 500,000			$ 500,000		$ 500,000
Unamortized Debt Discount and Debt Issuance Cost						(3,400)			(3,400)		(3,727)
Total Carrying Value of Long-Term Debt						$ 496,600			$ 496,600		$ 496,273
Description of Senior Notes
Aggregate principal amount																							$ 500,000
Interest rate on Long-term Debt						3.65%			3.65%		3.65%					3.65%				3.65%			3.65%
Debt financing costs paid												3,200
Unamortized debt discount																							$ 1,300
Effective interest rate at debt origination or modification																							3.68%
3.6% Senior Notes due June 2026
Debt Instrument
Outstanding Principal Amount						$ 1,000,000			$ 1,000,000		$ 1,000,000
Unamortized Debt Discount and Debt Issuance Cost						(7,035)			(7,035)		(7,619)
Total Carrying Value of Long-Term Debt						$ 992,965			$ 992,965		$ 992,381
Description of Senior Notes
Aggregate principal amount																					$ 1,000,000
Interest rate on Long-term Debt						3.60%			3.60%		3.60%					3.60%				3.60%	3.60%
Debt financing costs paid											$ 6,200
Unamortized debt discount																					$ 1,900
Effective interest rate at debt origination or modification																					3.62%
1.8% (€1 Billion) Senior Notes due March 2027
Debt Instrument
Outstanding Principal Amount						$ 1,182,200			$ 1,182,200		1,054,750
Unamortized Debt Discount and Debt Issuance Cost						(5,270)			(5,270)		(5,655)
Total Carrying Value of Long-Term Debt						$ 1,176,930			$ 1,176,930		$ 1,049,095
Description of Senior Notes
Aggregate principal amount | €																€ 1,000.0				€ 1,000.0				€ 1,000.0
Interest rate on Long-term Debt						1.80%			1.80%		1.80%					1.80%				1.80%				1.80%
Debt financing costs paid												$ 6,300
Unamortized debt discount | €																								€ 0.3
Effective interest rate at debt origination or modification																								1.80%
3.55% Senior Notes due March 2028
Debt Instrument
Outstanding Principal Amount						$ 500,000			$ 500,000
Unamortized Debt Discount and Debt Issuance Cost						(3,578)			(3,578)
Total Carrying Value of Long-Term Debt						$ 496,422			$ 496,422
Description of Senior Notes
Aggregate principal amount																	$ 500,000
Interest rate on Long-term Debt						3.55%			3.55%							3.55%	3.55%
Debt financing costs paid						$ 3,100
Unamortized debt discount																	$ 400
Effective interest rate at debt origination or modification																	3.56%
Convertible Debt
Description of Senior Notes
Interest expense related to debt						23,400		23,700	$ 71,400	70,600
Coupon Interest expense						5,400		5,600	16,400	16,800
Amortization of debt discount included in interest expense						16,900		16,900	51,400	50,400
Amortization of debt issuance costs						$ 1,100		$ 1,200	$ 3,600	$ 3,400
Debt, weighted average interest rate						3.40%		3.40%	3.40%	3.40%
Other Long-term Debt
Description of Senior Notes
Interest expense related to debt						$ 38,500		$ 30,800	$ 102,200	$ 77,700
Coupon Interest expense						36,900		29,700	98,100	74,800
Amortization of debt discount included in interest expense						600		400	1,500	1,100
Amortization of debt issuance costs						1,000		$ 700	2,600	$ 1,800
1% CT Loan Due March 2016
Description of Senior Notes
Aggregate principal amount	$ 2,500					$ 1,500			$ 1,500		$ 2,500
Interest rate on Long-term Debt	1.00%					1.00%			1.00%		1.00%					1.00%				1.00%
Debt instrument, term	10 years
Debt instrument, decrease, forgiveness							$ 1,000
Minimum | 1.0% Convertible Senior Notes due March 2018
Description of Senior Notes
Minimum and Maximum consecutive days the closing sales price of common stock must exceed a specified percentage of conversion price to trigger conversion feature of note (in days) | Days					20
Additional payment to debt holder, settled In shares, aggregate value					$ 0
Minimum | 0.35% Convertible Senior Notes due June 2020
Description of Senior Notes
Minimum and Maximum consecutive days the closing sales price of common stock must exceed a specified percentage of conversion price to trigger conversion feature of note (in days) | Days				20
Additional payment to debt holder, settled In shares, aggregate value				$ 0
Minimum | 0.9% Convertible Senior Notes due September 2021
Description of Senior Notes
Minimum and Maximum consecutive days the closing sales price of common stock must exceed a specified percentage of conversion price to trigger conversion feature of note (in days) | Days		20
Additional payment to debt holder, settled In shares, aggregate value		$ 0
Maximum | 1.0% Convertible Senior Notes due March 2018
Description of Senior Notes
Minimum and Maximum consecutive days the closing sales price of common stock must exceed a specified percentage of conversion price to trigger conversion feature of note (in days) | Days					30
Additional payment to debt holder, settled In shares, aggregate value					$ 344,000
Maximum | 0.35% Convertible Senior Notes due June 2020
Description of Senior Notes
Minimum and Maximum consecutive days the closing sales price of common stock must exceed a specified percentage of conversion price to trigger conversion feature of note (in days) | Days				30
Additional payment to debt holder, settled In shares, aggregate value				$ 397,000
Maximum | 0.9% Convertible Senior Notes due September 2021
Description of Senior Notes
Minimum and Maximum consecutive days the closing sales price of common stock must exceed a specified percentage of conversion price to trigger conversion feature of note (in days) | Days		30
Additional payment to debt holder, settled In shares, aggregate value		$ 375,000
Level 2
Description of Senior Notes
Estimated market value of outstanding debt						$ 11,500,000			$ 11,500,000		$ 8,400,000
Momondo Group [Member]
Description of Senior Notes
Assumed Debt																		$ 15,100
Subsequent Event [Member] | 1.0% Convertible Senior Notes due March 2018
Description of Senior Notes
Payments Related to Conversion of Senior Notes			$ 196,100