Business Combinations - Preliminary Allocation of Estimated Merger Consideration to the Identifiable Tangible and Intangible Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Mar. 08, 2019		Dec. 31, 2018
Business Acquisition [Line Items]
Goodwill, net	$ 780,351			$ 334,680
Nutrisystem, Inc.
Business Acquisition [Line Items]
Cash, cash equivalents, and short-term investments		$ 81,217
Accounts receivable		22,639
Inventory		38,494
Prepaid expenses and other current assets		12,345
Property and equipment		31,233
Right-of-use assets		22,145
Intangible assets		948,000
Other assets/liabilities		7,161
Accounts payable		(58,253)
Accrued salaries and benefits and other liabilities		(8,695)
Deferred revenue		(13,339)
Lease liabilities		(22,145)
Deferred tax liabilities, net		(220,365)
Total identifiable assets and liabilities acquired		840,437
Goodwill, net	$ 445,671	445,671	[1]
Total Merger Consideration		$ 1,286,108

[1] Goodwill represents the excess of merger consideration over the preliminary fair value of the underlying assets acquired and liabilities assumed. Goodwill is attributable to the assembled workforce of experienced personnel at Nutrisystem and synergies expected to be achieved from the combined operations of Tivity Health and Nutrisystem.