Note 8 - Fair Value Measurements - Summary of Assets Measured on Recurring Basis (Details) - Cash and Investments Held in Trust Account [Member] - Fair Value, Recurring [Member] - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Inputs, Level 1 [Member]
Cash and marketable securities held in Trust Account	$ 391,964,540	$ 418,727,517
Fair Value, Inputs, Level 2 [Member]
Cash and marketable securities held in Trust Account
Fair Value, Inputs, Level 3 [Member]
Cash and marketable securities held in Trust Account