Acquisitions - Narrative (Details) $ / shares in Units, $ in Thousands			1 Months Ended	12 Months Ended
	Jun. 01, 2020 USD ($) office $ / shares shares	May 29, 2020 USD ($) $ / shares	Jun. 30, 2020 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	May 31, 2020 USD ($) client_account
Business Acquisition [Line Items]
Assets				$ 21,094,429	$ 19,736,544
Total gross loans				14,295,897	13,236,433
Total deposits				17,115,589	16,214,177
Goodwill				901,312	898,569	$ 808,322
Purchase accounting adjustments				2,743	(2,597)
ACL expense (reversal)				(67,069)	172,262	$ 7,135
Initial ACL Recorded for PCD Loans					21,242
PENSCO
Business Acquisition [Line Items]
Custodial assets							$ 14,480,000
Number of client accounts | client_account							44,000
Opus
Business Acquisition [Line Items]
Equity issued, ratio	0.900
Stock transaction value (usd per share) | $ / shares	$ 19.31
Closing price for the Corporation's common stock (in dollars per share) | $ / shares		$ 21.62
Total merger consideration	$ 749,605	$ 749,605
Intangible assets	19,267
Goodwill	92,990
Purchase accounting adjustments			$ (146)	2,700
Fair value of non-PCD loans	4,940,000
Aggregate fair value of PCD loans acquired	841,234
Contractual balance of non-PCD loans	5,050,000
Contractual balance of PCD loans	896,483
ACL expense (reversal)	75,900				75,900
Initial ACL Recorded for PCD Loans	21,200				$ 21,200
Merger-related expense				$ 5
Opus | Core Deposits
Business Acquisition [Line Items]
Intangible assets	16,100
Opus | Customer Relationships
Business Acquisition [Line Items]
Intangible assets	$ 3,200
Opus | Common Stock
Business Acquisition [Line Items]
Number of shares of common stock issued as consideration (in shares) | shares	34,407,403
Common stock issued for tax withholding (in shares) | shares	165,136
Value of equity interests issued and issuable		747,458
Opus | Equity warrants
Business Acquisition [Line Items]
Number of shares of common stock issued as consideration (in shares) | shares	406,778
Value of equity interests issued and issuable	$ 1,800
Opus | Equity Option
Business Acquisition [Line Items]
Number of shares of common stock issued as consideration (in shares) | shares	9,538
Value of equity interests issued and issuable	$ 46
Opus | Restricted Stock
Business Acquisition [Line Items]
Value of equity interests issued and issuable	328	$ 328
Opus | Opus
Business Acquisition [Line Items]
Assets	8,320,000
Total gross loans	5,940,000
Total deposits	$ 6,910,000
Number of banking offices | office	46