Earnings (Loss) Per Share - Reconciliation of the Numerator and Denominator of Basic and Diluted Earnings (Loss) Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended																12 Months Ended
		Dec. 31, 2021	[1]	Sep. 30, 2021		Jun. 30, 2021		Mar. 31, 2021		Dec. 31, 2020	[2]	Sep. 30, 2020		Jun. 30, 2020		Mar. 31, 2020		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Numerator [Abstract]
Income from continuing operations attributable to Tivity Health, Inc. - numerator for earnings (loss) per share		$ (25,038)		$ 103,699		$ 8,771		$ 19,944		$ 14,642		$ 16,750		$ 17,202		$ 8,275		$ 107,376	$ 56,869	$ 45,217
Net income (loss) from discontinued operations attributable to Tivity Health, Inc. - numerator for earnings (loss) per share		(308)		(932)		(414)		(808)		(26,260)		(59,168)		11,309		(206,381)		(2,462)	(280,500)	(332,038)
Net income (loss)		$ (25,346)		$ 102,767		$ 8,357		$ 19,136		$ (11,618)		$ (42,418)		$ 28,511		$ (198,106)		$ 104,914	$ (223,631)	$ (286,821)
Denominator [Abstract]
Shares used for basic income (loss) per share																		49,573	48,746	46,509
Effect of dilutive stock options and restricted stock units outstanding [Abstract]
Shares used for diluted income (loss) per share																		50,424	49,217	47,103
Earnings (loss) per share attributable to Tivity Health, Inc. - basic [Abstract]
Continuing operations (in dollars per share)		$ (0.50)	[3]	$ 2.09	[3]	$ 0.18	[3]	$ 0.41	[3]	$ 0.30	[3]	$ 0.34	[3]	$ 0.35	[3]	$ 0.17	[3]	$ 2.17	$ 1.17	$ 0.97
Discontinued operations (in dollars per share)		(0.01)	[3]	(0.02)	[3]	(0.01)	[3]	(0.02)	[3]	(0.54)	[3]	(1.21)	[3]	0.23	[3]	(4.25)	[3]	(0.05)	(5.75)	(7.14)
Net income (loss)	[4]	(0.51)	[3]	2.07	[3]	0.17	[3]	0.39	[3]	(0.24)	[3]	(0.87)	[3]	0.59	[3]	(4.08)	[3]	2.12	(4.59)	(6.17)
Earnings (loss) per share attributable to Tivity Health, Inc. - diluted [Abstract]
Continuing operations (in dollars per share)		(0.50)	[3]	2.06	[3]	0.17	[3]	0.40	[3]	0.29	[3]	0.34	[3]	0.35	[3]	0.17	[3]	2.13	1.16	0.96
Discontinued operations (in dollars per share)		(0.01)	[3]	(0.02)	[3]	(0.01)	[3]	(0.02)	[3]	(0.53)	[3]	(1.20)	[3]	0.23	[3]	(4.22)	[3]	(0.05)	(5.70)	(7.05)
Net income (loss)		$ (0.50)	[3],[4]	$ 2.04	[3],[4]	$ 0.17	[3],[4]	$ 0.38	[3],[4]	$ (0.23)	[3],[4]	$ (0.86)	[3],[4]	$ 0.58	[3],[4]	$ (4.05)	[3],[4]	$ 2.08	$ (4.54)	$ (6.09)
Non-Qualified Stock Options
Effect of dilutive stock options and restricted stock units outstanding [Abstract]
Effect of dilutive stock options and restricted stock units outstanding (in shares)																		60	29	90
Restricted Stock Units (RSUs)
Effect of dilutive stock options and restricted stock units outstanding [Abstract]
Effect of dilutive stock options and restricted stock units outstanding (in shares)																		538	412	489
Market Stock Units
Effect of dilutive stock options and restricted stock units outstanding [Abstract]
Effect of dilutive stock options and restricted stock units outstanding (in shares)																		184	1
Performance-Based Stock Units
Effect of dilutive stock options and restricted stock units outstanding [Abstract]
Effect of dilutive stock options and restricted stock units outstanding (in shares)																		69	29	15
Non-Qualified Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Dilutive securities outstanding not included in the computation of earnings (loss) per share because their effect is anti-dilutive (in shares)																		226	186	70
Restricted Stock Units (RSUs)
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Dilutive securities outstanding not included in the computation of earnings (loss) per share because their effect is anti-dilutive (in shares)																		20	242	192
Restricted Stock Awards
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Dilutive securities outstanding not included in the computation of earnings (loss) per share because their effect is anti-dilutive (in shares)																			26	102
Performance-Based Stock Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Dilutive securities outstanding not included in the computation of earnings (loss) per share because their effect is anti-dilutive (in shares)																			24

[1] Loss from continuing operations for the fourth quarter of 2021 includes an unrealized loss of $41.4 million related to the change in fair value of the Sharecare Equity Security and an unrealized gain of $1.9 million related to the de-designated swaps, each of which was recorded to other (income) expense, net. The income tax benefit that would have otherwise resulted from the unrealized loss of $41.4 million was fully offset by income tax expense due to an increase in the valuation allowance on deferred tax assets related to capital loss carryforwards; therefore, there was no net income tax benefit associated with this loss.  In addition, loss from continuing operations for the fourth quarter of 2021 includes a total of $0.5 million related to CEO transition costs, acquisition and integration costs, and project costs, which was primarily recorded to selling, general, and administrative expenses. Finally, the impact of potentially dilutive securities for the three months ended December 31, 2021 was not considered because the impact would be anti-dilutive.

[2] Income from continuing operations for the fourth quarter of 2020 includes strategic project costs, CEO transition costs, and acquisition and integration costs of $2.3 million, $1.0 million, and $0.6 million, respectively, each of which were primarily recorded to selling, general, and administrative expenses.

[3] We calculated earnings per share for each of the quarters based on the weighted average number of shares and dilutive securities outstanding for each period. Accordingly, the sum of the quarters may not necessarily be equal to the full year income per share.

[4] Figures may not add due to rounding.