Related Party Transactions - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Related Party Transaction [Line Items]
Total revenue from related parties	$ 770,000	$ 1,049,000
SK Engineering & Construction Co., Ltd.
Related Party Transaction [Line Items]
Accounts receivable	0	0
Equity Method Investee | Softbank Corp.
Related Party Transaction [Line Items]
Accounts receivable	400,000
Service | Equity Method Investee | Softbank Corp.
Related Party Transaction [Line Items]
Total revenue from related parties	$ 800,000	$ 1,000,000.0