SIGNIFICANT ACCOUNTING POLICIES (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Goodwill and Indefinite-Lived Intangible Assets
Goodwill and indefinite-lived intangible asset impairments	$ 0
Advertising
Advertising expense	$ 80,700,000	$ 40,800,000
Computer equipment and capitalized software | Minimum
Property and Equipment
Depreciation period	1 year
Computer equipment and capitalized software | Maximum
Property and Equipment
Depreciation period	5 years
Furniture and other equipment | Minimum
Property and Equipment
Depreciation period	3 years
Furniture and other equipment | Maximum
Property and Equipment
Depreciation period	7 years
Software development | Minimum
Property and Equipment
Depreciation period	1 year
Software development | Maximum
Property and Equipment
Depreciation period	3 years