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Organization and Basis of Presentation - Summary of Subsidiaries VIEs and VIEs' Subsidiaries (Details)	12 Months Ended
	Dec. 31, 2019
Variable Interest Entity [Line Items]
Place of establishment	E9
Sunlands HK
Variable Interest Entity [Line Items]
Date of establishment/ acquisition	Oct. 06, 2015
Place of establishment	K3
Percentage of direct or indirect economic ownership	100.00%
Principal activities	Investment holding
Wuhan Zhibo
Variable Interest Entity [Line Items]
Date of establishment/ acquisition	Aug. 02, 2017
Place of establishment	F4
Percentage of direct or indirect economic ownership	100.00%
Principal activities	Provision of technical consultation and services
Tianjin Sunlands
Variable Interest Entity [Line Items]
Date of establishment/ acquisition	Jul. 31, 2017
Place of establishment	F4
Percentage of direct or indirect economic ownership	100.00%
Principal activities	Provision of technical consultation and services
Wuhan Shangde Online Education Technology Co., Ltd.
Variable Interest Entity [Line Items]
Date of establishment/ acquisition	Jun. 25, 2019
Place of establishment	F4
Percentage of direct or indirect economic ownership	100.00%
Principal activities	Provision of education services
Chengdu Xinketang Cultural Communication Co., Ltd.
Variable Interest Entity [Line Items]
Date of establishment/ acquisition	Nov. 04, 2019
Place of establishment	F4
Percentage of direct or indirect economic ownership	100.00%
Principal activities	Sales of educational materials and books
Beijing Sunlands
Variable Interest Entity [Line Items]
Date of establishment/ acquisition	Sep. 27, 2013
Place of establishment	F4
Principal activities	Investment holding and provision of education services
Tianjin Shangde
Variable Interest Entity [Line Items]
Date of establishment/ acquisition	Mar. 21, 2018
Place of establishment	F4
Principal activities	Provision of education services
Beijing Shangzhi Jiaye Education Technology Co., Ltd
Variable Interest Entity [Line Items]
Date of establishment/ acquisition	Mar. 13, 2012
Place of establishment	F4
Percentage of direct or indirect economic ownership	100.00%
Principal activities	Provision of education services
Beijing Shangren Chongye Education Technology Co., Ltd.
Variable Interest Entity [Line Items]
Date of establishment/ acquisition	Sep. 27, 2013
Place of establishment	F4
Percentage of direct or indirect economic ownership	100.00%
Principal activities	Provision of education services
Guangdong Shangde Online Education Technology Co., Ltd.
Variable Interest Entity [Line Items]
Date of establishment/ acquisition	Oct. 15, 2013
Place of establishment	F4
Percentage of direct or indirect economic ownership	100.00%
Principal activities	Provision of education services
Guangzhou Youhe Self-study Training School
Variable Interest Entity [Line Items]
Date of establishment/ acquisition	May 19, 2015
Place of establishment	F4
Percentage of direct or indirect economic ownership	100.00%
Principal activities	Provision of education services
Beijing Heikuaima Education Technology Co., Ltd.
Variable Interest Entity [Line Items]
Date of establishment/ acquisition	Mar. 03, 2016
Place of establishment	F4
Percentage of direct or indirect economic ownership	100.00%
Principal activities	Provision of education services
Shanghai Shangchi Education Technology Co., Ltd.
Variable Interest Entity [Line Items]
Date of establishment/ acquisition	Dec. 22, 2016
Place of establishment	F4
Percentage of direct or indirect economic ownership	90.00%
Principal activities	Provision of education services
Shanghai Shangchi Institute
Variable Interest Entity [Line Items]
Date of establishment/ acquisition	Sep. 01, 2017
Place of establishment	F4
Percentage of direct or indirect economic ownership	100.00%
Principal activities	Provision of education services
Guangzhou Shangzhi Side Education Technology Co., Ltd.
Variable Interest Entity [Line Items]
Date of establishment/ acquisition	Sep. 28, 2017
Place of establishment	F4
Percentage of direct or indirect economic ownership	100.00%
Principal activities	Provision of education services

X

- Definition

Date when an entity was incorporated

+ References

No definition available.

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- Definition

Two-character EDGAR code representing the state or country of incorporation.

+ References

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- Definition

The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

+ References

No definition available.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Description of the transactions or business conducted by the Variable Interest Entity (VIE), including how the VIE is financed.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 16
-Subparagraph (c,d)
-URI http://asc.fasb.org/extlink&oid=118582676&loc=SL6228967-111685

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 5A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=118582676&loc=SL6759159-111685

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph b
-URI http://asc.fasb.org/extlink&oid=118582676&loc=d3e5747-111685

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118582676&loc=d3e5728-111685

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118582676&loc=d3e5747-111685

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