Intangible Assets - Summary Of Intangible Assets and Accumulated Amortization Included In The Consolidated Statements of Condition (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Intangible Assets [Line Items]
Gross Carrying Amount	$ 185,772	$ 240,637
Accumulated Amortization	(60,880)	(110,437)
Net Carrying Value	124,892	130,200
Core deposit intangibles
Intangible Assets [Line Items]
Gross Carrying Amount	157,150	157,150
Accumulated Amortization	(51,966)	(47,372)
Net Carrying Value	105,184	109,778
Customer relationships (a)
Intangible Assets [Line Items]
Gross Carrying Amount	23,000	77,865
Accumulated Amortization	(5,734)	(60,150)
Net Carrying Value	17,266	17,715
Finite-lived intangible assets, fully amortized		54,900
Other
Intangible Assets [Line Items]
Gross Carrying Amount	5,622	5,622
Accumulated Amortization	(3,180)	(2,915)
Net Carrying Value	2,442	2,707
State banking licenses
Intangible Assets [Line Items]
Indefinite-lived intangible assets, excluding goodwill	$ 300	$ 300