Intangible Assets and Goodwill - Change in Carrying Amount of Goodwill (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2019 USD ($)
Goodwill And Intangible Assets Disclosure [Abstract]
Balance, January 1, 2019	$ 334,680
Acquisition of Nutrisystem	445,671
Measurement period adjustment	11,384	[1]
Balance, September 30, 2019	$ 791,735

[1] See Note 2 for explanation.