STOCKHOLDERS' EQUITY (Narrative) (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($) $ / shares shares	Sep. 30, 2019 USD ($) shares	Sep. 30, 2020 USD ($) schedule plan $ / shares shares	Sep. 30, 2019 USD ($) $ / shares shares	Jan. 31, 2020 USD ($)	Feb. 11, 2019 USD ($)	Nov. 27, 2018 USD ($)	Jul. 31, 2017 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Treasury stock (in shares) | shares		0		0
Number of equity incentive plans | plan			3
Granted (in shares) | shares			146,500
Fair value as of vest date of RSUs			$ 64,100,000	$ 84,900,000
Stock-based compensation	$ 30,255,000	$ 29,236,000	92,590,000	91,006,000
Capitalized stock-based compensation expense	$ 2,600,000	2,600,000	$ 7,100,000	7,600,000
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Target vesting range	0.00%		0.00%
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Target vesting range	200.00%		200.00%
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of vesting schedules | schedule			3
Exercisable period			10 years
Intrinsic value of options exercised	$ 700,000	$ 3,400,000	$ 5,100,000	$ 6,200,000
Weighted average grant date fair value (in USD per share) | $ / shares	$ 7.61		$ 9.69	$ 17.64
Granted (in shares) | shares		0
Unrecognized compensation costs	$ 10,600,000		$ 10,600,000
Unrecognized compensation costs, period for recognition			2 years 1 month 6 days
Employee Stock Option | End of year one
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rate			25.00%
Employee Stock Option | First year
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rate			10.00%
Employee Stock Option | Second year
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rate			20.00%
Employee Stock Option | Third year
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rate			30.00%
Employee Stock Option | Fourth year
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rate			40.00%
Employee Stock Option | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			3 years
Employee Stock Option | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			4 years
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			4 years
Number of vesting schedules | schedule			3
Unrecognized compensation costs	$ 229,300,000		$ 229,300,000
Unrecognized compensation costs, period for recognition			2 years 6 months
RSUs | End of year one
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rate			25.00%
RSUs | First year
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rate			10.00%
RSUs | Second year
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rate			20.00%
RSUs | Third year
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rate			30.00%
RSUs | Fourth year
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rate			40.00%
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			4 years
Performance goal stock price at which Performance Restricted Stock Unit awards would vest (usd per share) | $ / shares	$ 45.3125		$ 45.3125
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant date fair value (in USD per share) | $ / shares			$ 18.48	$ 26.12
Subscription rate of eligible compensation	15.00%		15.00%
Purchase price, percentage of fair market value			85.00%
Number of shares purchased (in shares) | shares	0	0	433,697	288,529
Stock-based compensation	$ 600,000	$ 700,000	$ 1,900,000	$ 2,000,000.0
July 2017 Share Repurchase Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock repurchase program, authorized amount	950,000,000.0		950,000,000.0		$ 250,000,000.0	$ 250,000,000.0	$ 250,000,000.0	$ 200,000,000.0
Remaining authorized repurchase amount	$ 269,000,000.0		$ 269,000,000.0
Stock repurchased (in shares) | shares			0
Stock repurchased and retired (in shares) | shares				13,994,909
Repurchased and retired amount				$ 475,000,000.0