CONSOLIDATED STATEMENT OF CHANGES IN STOCKHOLDERS' EQUITY AND REDEEMABLE UNITS AND STOCKHOLDRE'S / MEMBERS' EQUITY - USD ($)	Total	IPO [Member]	Class A Redeemable Units [Member]	Class A-1 Common Units [Member]	Class A-2 Common Units [Member]	Class B Common Units [Member]	Common Stock [Member]	Common Stock [Member] IPO [Member]	Common Stock [Member] Class A-1 Common Units [Member]	Common Stock [Member] Class A-2 Common Units [Member]	Common Stock [Member] Class B Common Units [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] IPO [Member]	Accumulated Deficit [Member]
Balance at Dec. 31, 2020	$ 997,836,000						$ 0		$ 959,563,000	$ 49,946,000	$ 0	$ 1,452,000		$ (13,125,000)
Temporary Equity, Shares Outstanding at Dec. 31, 2020			35,000
Temporary Equity, Carrying Amount, Attributable to Parent at Dec. 31, 2020			$ 35,000,000
Shares, Outstanding at Dec. 31, 2020				959,563	49,946	0	0
Net loss	(78,715,000)													(78,715,000)
Issuance of common units	1,000,000	$ 548,905,000			$ 1,000,000			$ 328,000					$ 548,577,000
Issuance of common , Shares					962			32,800
Accretion of redeemable class A units	(36,750,000)		(36,750,000)											(36,750,000)
Issuance of common units for acquisitions of businesses	1,486,000				$ 1,486,000
Issuance of common units for acquisitions of businesses, shares					725
Vested class B profits interests						17,920
Conversion of Redeemable Class A Units into common stock upon closing of initial public offering, Value	71,750,000		$ (71,750,000)				$ 102,000					71,648,000
Conversion of Redeemable Class A Units into common stock upon closing of initial public offering, shares			(35,000)				(10,234)
Conversion of common units into common stock upon closing of initial public offering, Value				$ (959,563,000)	$ (52,432,000)		$ 2,957,000					1,009,038,000
Conversion of common units into common stock upon closing of initial public offering, shares				(959,563)	(51,633)		(295,663)
Conversion of vested class profits interests to common stock upon closing of initial public offering, shares						(17,920)	(4,186)
Conversion of vested class B profits interests to common stock upon closing of initial public offering, value							$ 42,000					(42,000)
Conversion of unvested class B profits interests to common stock upon closing of initial public offering, value							$ 308,000					(308,000)
Conversion of unvested class profits interests to common stock upon closing of initial public offering , shares							30,766
Endowment of shares to the LifeStance Health Foundation, shares							500
Endowment of shares to the LifeStance Health Foundation, value	9,000,000						$ 5,000					8,995,000
Stock and unit-based compensation expense	30,120,000											30,120,000
Balance at Jun. 30, 2021	1,544,632,000						$ 3,742,000		0	0	0	1,669,480,000		(128,590,000)
Temporary Equity, Shares Outstanding at Jun. 30, 2021			0
Temporary Equity, Carrying Amount, Attributable to Parent at Jun. 30, 2021			$ 0
Shares, Outstanding at Jun. 30, 2021				0	0	0	374,149
Balance at Mar. 31, 2021	954,009,000						$ 0		959,563,000	50,946,000	0	2,057,000		(58,557,000)
Temporary Equity, Shares Outstanding at Mar. 31, 2021			35,000
Temporary Equity, Carrying Amount, Attributable to Parent at Mar. 31, 2021			$ 71,750,000
Shares, Outstanding at Mar. 31, 2021				959,563	50,908	0	0
Net loss	(70,033,000)													(70,033,000)
Issuance of common units		$ 548,905,000						$ 328,000					$ 548,577,000
Issuance of common , Shares								32,800
Accretion of redeemable class A units	0
Issuance of common units for acquisitions of businesses	1,486,000				$ 1,486,000
Issuance of common units for acquisitions of businesses, shares					725
Vested class B profits interests						17,920
Conversion of Redeemable Class A Units into common stock upon closing of initial public offering, Value	71,750,000		$ (71,750,000)				$ 102,000					71,648,000
Conversion of Redeemable Class A Units into common stock upon closing of initial public offering, shares			(35,000)				(10,234)
Conversion of common units into common stock upon closing of initial public offering, Value				$ (959,563,000)	$ (52,432,000)		$ 2,957,000					1,009,038,000
Conversion of common units into common stock upon closing of initial public offering, shares				(959,563)	(51,633)		(295,663)
Conversion of vested class profits interests to common stock upon closing of initial public offering, shares						17,920	(4,186)
Conversion of vested class B profits interests to common stock upon closing of initial public offering, value							$ 42,000					(42,000)
Conversion of unvested class B profits interests to common stock upon closing of initial public offering, value							$ 308,000					(308,000)
Conversion of unvested class profits interests to common stock upon closing of initial public offering , shares							30,766
Endowment of shares to the LifeStance Health Foundation, shares							500
Endowment of shares to the LifeStance Health Foundation, value	9,000,000						$ 5,000					8,995,000
Stock and unit-based compensation expense	29,515,000											29,515,000
Balance at Jun. 30, 2021	1,544,632,000						$ 3,742,000		$ 0	$ 0	$ 0	1,669,480,000		(128,590,000)
Temporary Equity, Shares Outstanding at Jun. 30, 2021			0
Temporary Equity, Carrying Amount, Attributable to Parent at Jun. 30, 2021			$ 0
Shares, Outstanding at Jun. 30, 2021				0	0	0	374,149
Balance at Dec. 31, 2021	1,545,028,000						$ 3,743,000					1,898,357,000		(357,072,000)
Shares, Outstanding at Dec. 31, 2021							374,255
Net loss	(131,055,000)													(131,055,000)
Issuance of common stock upon vesting of restricted stock units	(37,000)						$ 20,000					(57,000)
Issuance of common stock upon vesting of restricted stock units , shares							$ 1,954,000
Forfeitures, value	(185,000)											(185,000)
Forfeitures, shares							(28)
Accretion of redeemable class A units	0
Issuance of common units for acquisitions of businesses	0
Stock and unit-based compensation expense	117,550,000											117,550,000
Balance at Jun. 30, 2022	1,531,301,000						$ 3,763,000					2,015,665,000		(488,127,000)
Shares, Outstanding at Jun. 30, 2022							376,181
Balance at Mar. 31, 2022	1,542,518,000						$ 3,744,000					1,958,174,000		(419,400,000)
Shares, Outstanding at Mar. 31, 2022							374,323
Net loss	(68,727,000)													(68,727,000)
Issuance of common stock upon vesting of restricted stock units							$ 19,000					(19,000)
Issuance of common stock upon vesting of restricted stock units , shares							1,858,000
Accretion of redeemable class A units	0
Stock and unit-based compensation expense	57,510,000											57,510,000
Balance at Jun. 30, 2022	$ 1,531,301,000						$ 3,763,000					$ 2,015,665,000		$ (488,127,000)
Shares, Outstanding at Jun. 30, 2022							376,181