Business Segment Information - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Fixed income	$ 44,813	$ 55,758	$ 128,016	$ 161,546
Deposit transactions and cash management	35,792	28,011	107,859	80,434
Brokerage, management fees and commissions	14,200	11,937	41,423	35,872
Trust services and investment management	7,438	6,953	22,847	21,304
Bankcard income	6,878	6,170	19,958	17,230
Bank-owned life insurance (BOLI)	4,337	3,539	14,103	11,137
Debt securities gains/(losses), net	0	1	52	450
Equity securities gains/(losses), net	212,859	5	212,924	5
All other income and commissions	22,655	43	65,332	29,051
Total noninterest income	348,972	112,417	612,514	357,029
Gain on sale of TRUPs loans			(3,777)	0
All other income and commissions (e)			2,469	13
Loss on sale of equity investments			(212,924)	(5)
Visa Class B Shares
Disaggregation of Revenue [Line Items]
Gain on sale of investments	212,900		212,900
Underwriting, Portfolio Advisory, and Other Noninterest Income
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	8,400		24,000
Regional Banking
Disaggregation of Revenue [Line Items]
Fixed income	103	135	314	348
Deposit transactions and cash management	34,008	26,620	103,275	76,288
Brokerage, management fees and commissions	14,200	11,937	41,423	35,872
Trust services and investment management	7,453	6,968	22,891	21,360
Bankcard income	6,999	6,057	19,921	16,894
Bank-owned life insurance (BOLI)	0	0	0	0
Debt securities gains/(losses), net	0	0	0	386
Equity securities gains/(losses), net	0	0	0	0
All other income and commissions	17,094	12,653	52,269	36,941
Total noninterest income	79,857	64,370	240,093	188,089
Fixed Income
Disaggregation of Revenue [Line Items]
Fixed income	40,937	55,623	123,929	161,198
Deposit transactions and cash management	3	0	9	0
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	183	180	1,153	635
Total noninterest income	41,123	55,803	125,091	161,833
Corporate
Disaggregation of Revenue [Line Items]
Fixed income	(5)	0	(5)	0
Deposit transactions and cash management	1,725	1,339	4,416	4,004
Brokerage, management fees and commissions	0	0	0	0
Trust services and investment management	(15)	(15)	(44)	(56)
Bankcard income	57	56	168	169
Bank-owned life insurance (BOLI)	4,337	3,539	14,103	11,137
Debt securities gains/(losses), net	0	1	52	64
Equity securities gains/(losses), net	212,859	5	212,924	5
All other income and commissions	3,661	(14,401)	9,051	(13,104)
Total noninterest income	222,619	(9,476)	240,665	2,219
All other income and commissions (e)			4,100
Loss on sale of equity investments		14,300		14,300
Non-Strategic
Disaggregation of Revenue [Line Items]
Fixed income	3,778	0	3,778	0
Deposit transactions and cash management	56	52	159	142
Brokerage, management fees and commissions	0	0	0	0
Trust services and investment management	0	0	0	0
Bankcard income	(178)	57	(131)	167
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	1,717	1,611	2,859	4,579
Total noninterest income	$ 5,373	$ 1,720	6,665	$ 4,888
Gain on sale of TRUPs loans			$ 3,800

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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Gain On Sale Of Held-To-Maturity Loans

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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.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
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-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
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The difference between the carrying value and the sale price of equity securities, not separately or otherwise categorized as trading or available-for-sale. This element includes investments in which the entity holds a small ownership stake (generally, less than 20% of the shares outstanding) and cannot exert significant influence.

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Amount of gain (loss) on sale or disposal of property, plant and equipment assets, including oil and gas property and timber property.

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The difference between the carrying value and the sale price of an investment. A gain would be recognized when the sale price of the investment is greater than the carrying value of the investment. This element refers to the Gain included in earnings and not to the cash proceeds of the sale.

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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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