Goodwill and Other Intangible Assets - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021	Sep. 30, 2021	Dec. 31, 2020
Goodwill [Line Items]
Goodwill	$ 901,312	$ 901,312	$ 900,204	$ 901,312	$ 898,569
Purchase accounting adjustments to goodwill	0	0	1,635
Net intangible assets	$ 65,978	69,571	81,364
Estimated amortization expense for remainder of fiscal year		14,000
Estimated amortization expense for 2023		12,300
Estimated amortization expense for 2024		11,100
Estimated amortization expense for 2025		10,000
Estimated amortization expense for 2026		8,900
Minimum
Goodwill [Line Items]
Weighted average useful life (in years)	6 years
Maximum
Goodwill [Line Items]
Weighted average useful life (in years)	11 years
Core Deposits
Goodwill [Line Items]
Net intangible assets	$ 63,400	66,900
Core Deposits | Minimum
Goodwill [Line Items]
Weighted average useful life (in years)	6 years
Core Deposits | Maximum
Goodwill [Line Items]
Weighted average useful life (in years)	11 years
Customer Relationships
Goodwill [Line Items]
Net intangible assets	$ 2,600	$ 2,700
Opus Bank
Goodwill [Line Items]
Purchase accounting adjustments to goodwill			$ 1,600