Fair Value Measurement - Narrative (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2019	Dec. 31, 2013	Sep. 30, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset		$ 0			$ 3,259
Derivative liability		0			10,677
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset		0			3,259
Derivative liability		0			10,677
Fair Value, Measurements, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset					3,259
Derivative liability					10,677
Level 3 fair value measurement		0			$ (7,418)	$ 34,338
Coursera Inc | Series B Preferred Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Share purchase (in shares)			1,020
Payment to acquire investment			$ 5,000
Gain on sale of investment	$ 6,100	$ 6,473
Fair value of an investment				$ 11,473