Business Segment Information - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Fixed income	$ 66,414	$ 37,697	$ 120,163	$ 83,203
Deposit transactions and cash management	32,374	36,083	63,995	72,067
Brokerage, management fees and commissions	14,120	13,740	26,753	27,223
Trust services and investment management	7,888	8,132	14,914	15,409
Bankcard income	6,355	7,195	13,307	13,990
Bank-owned life insurance (BOLI)	5,126	5,773	9,528	9,766
Debt securities gains/(losses), net	(267)	0	(267)	52
Equity securities gains/(losses), net	316	31	347	65
All other income and commissions (Note 8)	25,667	18,874	50,298	41,767
Total noninterest income	157,993	127,525	299,038	263,542
Gain on sale of a building				3,300
Regional Banking
Disaggregation of Revenue [Line Items]
Fixed income	46	131	63	212
Deposit transactions and cash management	30,608	34,511	60,611	69,230
Brokerage, management fees and commissions	14,118	13,740	26,748	27,223
Trust services and investment management	7,902	8,147	14,958	15,438
Bankcard income	6,594	7,202	13,634	13,831
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 8)	22,207	17,036	38,491	35,121
Total noninterest income	81,475	80,767	154,505	161,055
Fixed Income
Disaggregation of Revenue [Line Items]
Fixed income	65,262	37,566	118,994	82,991
Deposit transactions and cash management	1	3	4	6
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 8)	359	794	431	970
Total noninterest income	65,622	38,363	119,429	83,967
Corporate
Disaggregation of Revenue [Line Items]
Fixed income	0	0	0	0
Deposit transactions and cash management	1,707	1,514	3,270	2,726
Brokerage, management fees and commissions	0	0	0	0
Trust services and investment management	(14)	(15)	(44)	(29)
Bankcard income	60	55	122	112
Bank-owned life insurance (BOLI)	5,126	5,773	9,528	9,766
Debt securities gains/(losses), net	(267)	0	(267)	52
Equity securities gains/(losses), net	316	31	347	65
All other income and commissions (Note 8)	2,472	1,380	9,796	5,362
Total noninterest income	9,400	8,738	22,752	18,054
Non-Strategic
Disaggregation of Revenue [Line Items]
Fixed income	1,106	0	1,106	0
Deposit transactions and cash management	58	55	110	105
Brokerage, management fees and commissions	2	0	5	0
Trust services and investment management	0	0	0	0
Bankcard income	(299)	(62)	(449)	47
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 8)	629	(336)	1,580	314
Total noninterest income	1,496	(343)	2,352	466
Underwriting, Portfolio Advisory, and Other Noninterest Income
Disaggregation of Revenue [Line Items]
Fixed income	$ 7,100	$ 7,400	$ 14,400	$ 15,600

Bankcard Other Income

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- Definition

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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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
-Paragraph 1
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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
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The difference between the carrying value and the sale price of real estate or properties that were intended to be sold or held for capital appreciation or rental income. This element refers to the gain (loss) included in earnings and not to the cash proceeds of the sale. This element is a noncash adjustment to net income when calculating net cash generated by operating activities using the indirect method.

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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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