Separation (Details) - USD ($) $ in Thousands, shares in Millions		12 Months Ended
	Jul. 26, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Restructuring Cost and Reserve [Line Items]
Separation costs, spinoff transaction		$ 56,624	$ 6,352	$ 0
GetGo, Inc.
Restructuring Cost and Reserve [Line Items]
Shares issued in acquisition (shares)	26.9
Minimum
Restructuring Cost and Reserve [Line Items]
Separation costs, spinoff transaction, total expected cost		120,000
Maximum
Restructuring Cost and Reserve [Line Items]
Separation costs, spinoff transaction, total expected cost		$ 130,000