Investments Other Investments (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	Mar. 21, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Schedule of Cost-method Investments [Line Items]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		$ (3,955)	$ (1,594)	$ (5,100)	$ (7,301)
Cost-method Investments, Realized Gain (Loss), Excluding Other than Temporary Impairments		7,624	0	7,624	0
Upserve [Member]
Schedule of Cost-method Investments [Line Items]
Disposition of Investment, Gross Consideration Received				16,000
Noncash or Part Noncash Divestiture, Amount of Consideration Received				1,300
Proceeds from Sale of Other Investments				14,700
Cost-method Investments, Realized Gain (Loss), Excluding Other than Temporary Impairments				(7,600)
Groupon Israel [Member]
Schedule of Cost-method Investments [Line Items]
Noncash or Part Noncash Divestiture, Amount of Consideration Received				2,300
Noncash or Part Noncash Acquisition, Investments Acquired	$ 400
Monster LP [Member]
Schedule of Cost-method Investments [Line Items]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		$ 3,800	$ 2,300	$ 1,500	$ 900