Fair Value Measurements - Measurements Levels (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	May 01, 2020	Dec. 31, 2019	Aug. 31, 2018	Jan. 12, 2018	Oct. 21, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrant shares (in shares)	414,286		1,339,286
ESW Holdings, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrant shares (in shares)	0	925,000	925,000		925,000
Warrants and Rights Outstanding, Maturity Date					Jan. 12, 2028
Hale Capital, LLP
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrant shares (in shares)	314,286		314,286
Warrants and Rights Outstanding, Maturity Date						Oct. 21, 2026
iStudy Co., Ltd.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrant shares (in shares)	100,000		100,000	100,000
Warrants and Rights Outstanding, Maturity Date				Aug. 31, 2028
Fair value, measurements, recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	$ 2,947		$ 2,900
Fair value, measurements, recurring | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	0
Fair value, measurements, recurring | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	0
Fair value, measurements, recurring | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	2,947
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value	2,947		2,939
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements	(1,855)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Issuances	140
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings	1,723
Fair value, measurements, recurring | Warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	2,910		2,939
Fair value, measurements, recurring | Warrants | ESW Holdings, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability			2,149
Fair value, measurements, recurring | Warrants | Hale Capital, LLP
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	2,245		645
Fair value, measurements, recurring | Warrants | iStudy Co., Ltd.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	665		145
Fair value, measurements, recurring | Warrants | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	0		0
Fair value, measurements, recurring | Warrants | Fair Value, Inputs, Level 1 | ESW Holdings, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability			0
Fair value, measurements, recurring | Warrants | Fair Value, Inputs, Level 1 | Hale Capital, LLP
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	0		0
Fair value, measurements, recurring | Warrants | Fair Value, Inputs, Level 1 | iStudy Co., Ltd.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	0		0
Fair value, measurements, recurring | Warrants | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	0		0
Fair value, measurements, recurring | Warrants | Fair Value, Inputs, Level 2 | ESW Holdings, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability			0
Fair value, measurements, recurring | Warrants | Fair Value, Inputs, Level 2 | Hale Capital, LLP
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	0		0
Fair value, measurements, recurring | Warrants | Fair Value, Inputs, Level 2 | iStudy Co., Ltd.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	0		0
Fair value, measurements, recurring | Warrants | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	2,910		2,939
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value	2,910		2,939
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements	(1,855)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings	1,826
Fair value, measurements, recurring | Warrants | Fair Value, Inputs, Level 3 | ESW Holdings, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability			2,149
Fair value, measurements, recurring | Warrants | Fair Value, Inputs, Level 3 | Hale Capital, LLP
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	2,245		645
Fair value, measurements, recurring | Warrants | Fair Value, Inputs, Level 3 | iStudy Co., Ltd.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	665		145
Fair value, measurements, recurring | Derivative
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	37
Fair value, measurements, recurring | Derivative | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	0
Fair value, measurements, recurring | Derivative | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	0
Fair value, measurements, recurring | Derivative | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	37
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value	37		$ 0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Issuances	140
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings	$ (103)