Revenue Recognition - Summary of Disaggregation of Revenue According to Revenue Stream and Business Segment (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation Of Revenue [Line Items]
Trading and investment banking	$ 4,653	$ 6,173	$ 8,754	$ 13,715
Gains on sales of securities available for sale, net	228	1,280	367	1,748
Other	8,026	8,675	18,627	15,191
Total noninterest income	100,289	110,306	205,814	213,223
Revenue (Expense) out of Scope of ASU 606 [Member] \| ASC 606 [Member]
Disaggregation Of Revenue [Line Items]
Trading and investment banking	4,653	6,004	8,754	13,041
Gains on sales of securities available for sale, net	228	1,280	367	1,748
Other	6,147	6,216	15,119	11,240
Total noninterest income	2,176	8,373	7,496	14,371
Trust and Securities Processing [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income	42,845	44,811	86,847	87,352
Service Charges On Deposit Accounts [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income	20,722	22,731	42,627	44,806
Noninterest income, including revenue from out of scope of ASU 606	20,722	22,731	42,627	44,806
Service Charges On Deposit Accounts [Member] \| Revenue (Expense) out of Scope of ASU 606 [Member] \| ASC 606 [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income, Revenue (Expense) out of Scope of ASU 606	35	30	69	60
Insurance Fees and Commissions [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income	340	513	641	1,159
Brokerage Fees [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income	6,291	5,889	12,644	11,266
Bankcard Fees [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income	17,184	20,234	35,307	37,986
Noninterest income, including revenue from out of scope of ASU 606	17,184	20,234	35,307	37,986
Bankcard Fees [Member] \| Revenue (Expense) out of Scope of ASU 606 [Member] \| ASC 606 [Member]
Disaggregation Of Revenue [Line Items]
Noninterest income, Revenue (Expense) out of Scope of ASU 606	(8,887)	(5,157)	(16,813)	(11,718)
Commercial Banking [Member]
Disaggregation Of Revenue [Line Items]
Total noninterest income	19,178	21,714	39,775	40,919
Commercial Banking [Member] \| Calculated under Revenue Guidance in Effect before Topic 606 [Member] \| ASC 606 [Member]
Disaggregation Of Revenue [Line Items]
Other	678	1,507	1,133	1,996
Total noninterest income	23,376	23,042	46,471	43,739
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	7,624	8,083	15,415	16,103
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	36	101	76
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	15,025	13,416	29,822	25,564
Institutional Banking [Member]
Disaggregation Of Revenue [Line Items]
Total noninterest income	43,411	48,161	88,830	93,828
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		169		674
Other	136	151	255	314
Total noninterest income	38,185	41,062	78,926	80,363
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	26,846	27,962	54,542	54,479
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	5,808	7,494	13,038	14,849
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	3,975	3,703	8,036	6,959
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	1,420	1,583	3,055	3,088
Personal Banking [Member]
Disaggregation Of Revenue [Line Items]
Total noninterest income	28,720	31,135	59,434	59,671
Personal Banking [Member] \| Calculated under Revenue Guidance in Effect before Topic 606 [Member] \| ASC 606 [Member]
Disaggregation Of Revenue [Line Items]
Other	879	708	1,785	1,472
Total noninterest income	27,846	28,983	55,724	56,801
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	15,999	16,849	32,305	32,873
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	2,777	2,864	5,589	5,729
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	340	513	641	1,159
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	2,267	2,147	4,507	4,228
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	5,584	5,902	10,897	11,340
Healthcare Services [Member]
Disaggregation Of Revenue [Line Items]
Total noninterest income	8,980	9,296	17,775	18,805
Healthcare Services [Member] \| Calculated under Revenue Guidance in Effect before Topic 606 [Member] \| ASC 606 [Member]
Disaggregation Of Revenue [Line Items]
Other	186	93	335	169
Total noninterest income	8,706	8,846	17,197	17,949
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	4,478	4,260	8,516	8,065
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		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	$ 4,042	$ 4,490	$ 8,346	$ 9,712

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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