Goodwill and Core Deposit Intangibles - Narrative (Details) - USD ($)				3 Months Ended				9 Months Ended	12 Months Ended
	Jul. 01, 2019	Apr. 08, 2019	Jul. 01, 2017	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Sep. 30, 2018	Sep. 30, 2018	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Impairment of goodwill	$ 0		$ 0
Goodwill [Line Items]
Amortization of intangible assets				$ 2,900,000		$ 2,300,000
Core Deposits
Goodwill [Line Items]
Amortization of intangible assets					$ 2,900,000		$ 2,300,000	$ 2,300,000	$ 2,900,000
Weighted average useful lives of related deposits		10 years							10 years