Business Segment Information - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Fixed income	$ 112,421	$ 66,414	$ 208,056	$ 120,163
Deposit transactions and cash management	30,787	32,374	61,077	63,995
Brokerage, management fees and commissions	13,800	14,120	29,205	26,753
Trust services and investment management	7,733	7,888	14,928	14,914
Bankcard income	6,652	6,355	13,905	13,307
Bank-owned life insurance (BOLI)	6,380	5,126	10,969	9,528
Debt securities gains (losses), net	0	(267)	0	(267)
Equity securities gains/(losses), net	(1,493)	316	(1,468)	347
All other income and commissions (Note 7)	29,989	25,667	44,353	50,298
Total noninterest income	206,269	157,993	381,025	299,038
Regional Banking
Disaggregation of Revenue [Line Items]
Fixed income	81	46	202	63
Deposit transactions and cash management	29,541	30,632	58,368	60,658
Brokerage, management fees and commissions	13,800	14,120	29,205	26,753
Trust services and investment management	7,750	7,902	14,963	14,958
Bankcard income	6,551	6,597	13,703	13,640
Bank-owned life insurance (BOLI)	0	0	0	0
Debt securities gains (losses), net	0	0	0	0
Equity securities gains/(losses), net	0	0	0	0
All other income and commissions (Note 7)	21,589	22,268	44,767	38,554
Total noninterest income	79,312	81,565	161,208	154,626
Fixed Income
Disaggregation of Revenue [Line Items]
Fixed income	112,340	65,262	207,854	118,994
Deposit transactions and cash management	0	1	0	4
Brokerage, management fees and commissions	0	0	0	0
Trust services and investment management	0	0	0	0
Bankcard income	0	0	0	0
Bank-owned life insurance (BOLI)	0	0	0	0
Debt securities gains (losses), net	0	0	0	0
Equity securities gains/(losses), net	0	0	0	0
All other income and commissions (Note 7)	895	359	1,104	431
Total noninterest income	113,235	65,622	208,958	119,429
Corporate
Disaggregation of Revenue [Line Items]
Fixed income	0	0	0	0
Deposit transactions and cash management	1,204	1,707	2,640	3,270
Brokerage, management fees and commissions	0	0	0	0
Trust services and investment management	(17)	(14)	(35)	(44)
Bankcard income	74	60	143	122
Bank-owned life insurance (BOLI)	6,380	5,126	10,969	9,528
Debt securities gains (losses), net	0	(267)	0	(267)
Equity securities gains/(losses), net	(1,493)	316	(1,468)	347
All other income and commissions (Note 7)	6,795	2,473	(3,024)	9,798
Total noninterest income	12,943	9,401	9,225	22,754
Non-Strategic
Disaggregation of Revenue [Line Items]
Fixed income	0	1,106	0	1,106
Deposit transactions and cash management	42	34	69	63
Brokerage, management fees and commissions	0	0	0	0
Trust services and investment management	0	0	0	0
Bankcard income	27	(302)	59	(455)
Bank-owned life insurance (BOLI)	0	0	0	0
Debt securities gains (losses), net	0	0	0	0
Equity securities gains/(losses), net	0	0	0	0
All other income and commissions (Note 7)	710	567	1,506	1,515
Total noninterest income	779	1,405	1,634	2,229
Underwriting, portfolio advisory, and other noninterest income
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	$ 8,800	$ 7,100	$ 18,100	$ 14,400

Bankcard Other Income

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Acting as an agent, a broker-dealer may buy and sell securities on behalf of its customers. In return for such services, the broker-dealer charges a commission. Each time a customer enters into a buy or sell transaction, a commission is earned by the broker-dealer for its selling and administrative efforts. For securities purchased, the commission is recorded as a receivable from customers; for securities sold, it is recorded as reductions in the payable to customers. Commissions earned are usually related to the broker-dealer's customers' trading volume and the dollar amounts of the trades. In general, commissions are for smaller trades of exchange-listed stocks and bonds made by retail customers. Revenue recognized in the period for (1) performance (incentive) fees based on the investment results achieved for management of certain institutional accounts and hedge funds, (2) schedule-based fees earned for management of mutual funds and closed-end funds, based either on average daily net assets or on a combination of the average daily net assets and gross income, and (3) other investment management and advisory fees.

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Deposit transactions and cash management.

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The major component of revenue in this line item is generated from the purchase and sale of securities as both principal and agent, and from other fee sources including loan sales, portfolio advisory, and derivative sales.

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Trust Services And Investment Management

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- Definition

Earnings on or other increases in the value of the cash surrender value of bank owned life insurance policies.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
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Amount of realized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), investment in debt security measured at amortized cost (held-to-maturity) and investment in debt security measured at fair value with change in fair value recognized in net income (trading).

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount of realized gain (loss) from sale of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
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The total amount of noninterest income which may be derived from: (1) fees and commissions; (2) premiums earned; (3) insurance policy charges; (4) the sale or disposal of assets; and (5) other sources not otherwise specified.

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Amount of revenue earned, classified as other, excluding interest income.

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Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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