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