Revenue Recognition - Summary of Disaggregation of Revenue According to Revenue Stream and Business Segment (Detail) - 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]
Trading and investment banking	$ 3,711	$ 4,453	$ 12,465	$ 18,168
Gains on sales of securities available for sale, net	211	2,390	578	4,138
Other	9,032	7,226	27,659	22,417
Total noninterest income	100,885	104,306	306,699	317,529
Revenue (Expense) out of Scope of ASC 606 [Member] \| ASC 606 [Member]
Disaggregation Of Revenue [Line Items]
Trading and investment banking	3,711	4,453	12,465	17,494
Gains on sales of securities available for sale, net	211	2,390	578	4,138
Other	6,865	5,760	21,984	17,000
Total noninterest income	1,536	4,724	9,032	19,095
Trust and Securities Processing [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income	43,425	45,060	130,272	132,412
Service Charges On Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income	20,927	21,510	63,554	66,316
Noninterest income, including revenue from out of scope of ASC 606	20,927	21,510	63,554	66,316
Service Charges On Deposit Accounts [Member] \| Revenue (Expense) out of Scope of ASC 606 [Member] \| ASC 606 [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income, Revenue (Expense) out of Scope of ASC 606	27	27	96	87
Insurance Fees and Commissions [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income	339	425	980	1,584
Brokerage Fees [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income	6,402	5,815	19,046	17,081
Bankcard Fees [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income	16,838	17,427	52,145	55,413
Noninterest income, including revenue from out of scope of ASC 606	16,838	17,427	52,145	55,413
Bankcard Fees [Member] \| Revenue (Expense) out of Scope of ASC 606 [Member] \| ASC 606 [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income, Revenue (Expense) out of Scope of ASC 606	(9,278)	(7,906)	(26,091)	(19,624)
Commercial Banking [Member]
Disaggregation Of Revenue [Line Items]
Total noninterest income	20,831	21,094	60,606	62,014
Commercial Banking [Member] \| Calculated under Revenue Guidance in Effect before Topic 606 [Member] \| ASC 606 [Member]
Disaggregation Of Revenue [Line Items]
Other	989	499	2,122	2,495
Total noninterest income	23,830	22,061	70,301	65,800
Commercial Banking [Member] \| Service Charges On Deposit Accounts [Member] \| Calculated under Revenue Guidance in Effect before Topic 606 [Member] \| ASC 606 [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income	7,502	7,579	22,917	23,682
Commercial Banking [Member] \| Brokerage Fees [Member] \| Calculated under Revenue Guidance in Effect before Topic 606 [Member] \| ASC 606 [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income	49	40	150	116
Commercial Banking [Member] \| Bankcard Fees [Member] \| Calculated under Revenue Guidance in Effect before Topic 606 [Member] \| ASC 606 [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income	15,290	13,943	45,112	39,507
Institutional Banking [Member]
Disaggregation Of Revenue [Line Items]
Total noninterest income	43,169	46,405	131,999	140,232
Institutional Banking [Member] \| Calculated under Revenue Guidance in Effect before Topic 606 [Member] \| ASC 606 [Member]
Disaggregation Of Revenue [Line Items]
Trading and investment banking				674
Other	121	160	376	474
Total noninterest income	38,926	40,696	117,852	121,059
Institutional Banking [Member] \| Trust and Securities Processing [Member] \| Calculated under Revenue Guidance in Effect before Topic 606 [Member] \| ASC 606 [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income	27,013	28,300	81,555	82,779
Institutional Banking [Member] \| Service Charges On Deposit Accounts [Member] \| Calculated under Revenue Guidance in Effect before Topic 606 [Member] \| ASC 606 [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income	6,140	7,025	19,178	21,874
Institutional Banking [Member] \| Brokerage Fees [Member] \| Calculated under Revenue Guidance in Effect before Topic 606 [Member] \| ASC 606 [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income	4,300	3,688	12,336	10,647
Institutional Banking [Member] \| Bankcard Fees [Member] \| Calculated under Revenue Guidance in Effect before Topic 606 [Member] \| ASC 606 [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income	1,352	1,523	4,407	4,611
Personal Banking [Member]
Disaggregation Of Revenue [Line Items]
Total noninterest income	28,266	28,261	87,700	87,932
Personal Banking [Member] \| Calculated under Revenue Guidance in Effect before Topic 606 [Member] \| ASC 606 [Member]
Disaggregation Of Revenue [Line Items]
Other	877	700	2,662	2,172
Total noninterest income	28,238	28,831	83,962	85,632
Personal Banking [Member] \| Trust and Securities Processing [Member] \| Calculated under Revenue Guidance in Effect before Topic 606 [Member] \| ASC 606 [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income	16,412	16,760	48,717	49,633
Personal Banking [Member] \| Service Charges On Deposit Accounts [Member] \| Calculated under Revenue Guidance in Effect before Topic 606 [Member] \| ASC 606 [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income	2,966	3,022	8,555	8,751
Personal Banking [Member] \| Insurance Fees and Commissions [Member] \| Calculated under Revenue Guidance in Effect before Topic 606 [Member] \| ASC 606 [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income	339	425	980	1,584
Personal Banking [Member] \| Brokerage Fees [Member] \| Calculated under Revenue Guidance in Effect before Topic 606 [Member] \| ASC 606 [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income	2,053	2,087	6,560	6,315
Personal Banking [Member] \| Bankcard Fees [Member] \| Calculated under Revenue Guidance in Effect before Topic 606 [Member] \| ASC 606 [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income	5,591	5,837	16,488	17,177
Healthcare Services [Member]
Disaggregation Of Revenue [Line Items]
Total noninterest income	8,619	8,546	26,394	27,351
Healthcare Services [Member] \| Calculated under Revenue Guidance in Effect before Topic 606 [Member] \| ASC 606 [Member]
Disaggregation Of Revenue [Line Items]
Other	180	107	515	276
Total noninterest income	8,355	7,994	25,552	25,943
Healthcare Services [Member] \| Service Charges On Deposit Accounts [Member] \| Calculated under Revenue Guidance in Effect before Topic 606 [Member] \| ASC 606 [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income	4,292	3,857	12,808	11,922
Healthcare Services [Member] \| Brokerage Fees [Member] \| Calculated under Revenue Guidance in Effect before Topic 606 [Member] \| ASC 606 [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income				3
Healthcare Services [Member] \| Bankcard Fees [Member] \| Calculated under Revenue Guidance in Effect before Topic 606 [Member] \| ASC 606 [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income	$ 3,883	$ 4,030	$ 12,229	$ 13,742

Noninterest income including out of scope of revenue from contract with customers.

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Amount of unrealized and realized gain (loss) on investment in debt and equity securities.

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Amount of fees and commissions from banking, advisory, brokerage, and securities underwriting activities. Activities include, but are not limited to, underwriting securities, private placements of securities, investment advisory and management services, merger and acquisition services, sale and servicing of mutual funds, and other related consulting fees.

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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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