Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	$ 72,825	$ 65,014	$ 145,553	$ 129,896
Noninterest Income (out-of-scope of Topic 606)	20,017	17,395	37,670	32,344
Total noninterest income	92,842	82,410	183,222	162,241
Insurance commissions and fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	23,996	20,853	46,644	42,473
Deposit Account [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	16,390	16,030	32,810	32,386
Card-Based and No Loan Fees [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	10,562	9,154	20,432	17,575
Fiduciary and Trust [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	13,437	12,346	26,806	24,281
Brokerage commissions and fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	6,896	4,346	14,169	8,679
Other revenue
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	1,545	2,286	4,692	4,502
Corporate and Commercial Specialty
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	3,320	4,426	8,515	9,184
Noninterest Income (out-of-scope of Topic 606)	10,874	8,071	18,361	15,306
Corporate and Commercial Specialty | Insurance commissions and fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	0	0	0	0
Corporate and Commercial Specialty | Deposit Account [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	3,786	4,070	8,011	8,511
Corporate and Commercial Specialty | Card-Based and No Loan Fees [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	358	320	674	592
Corporate and Commercial Specialty | Fiduciary and Trust [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	0	0	0	0
Corporate and Commercial Specialty | Brokerage commissions and fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	0	0	0	0
Corporate and Commercial Specialty | Other revenue
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	(825)	37	(170)	82
Community, Consumer, and Business
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	69,349	60,507	136,547	120,547
Noninterest Income (out-of-scope of Topic 606)	6,901	5,302	13,739	10,132
Community, Consumer, and Business | Insurance commissions and fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	23,988	20,853	46,612	42,473
Community, Consumer, and Business | Deposit Account [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	12,590	11,938	24,773	23,826
Community, Consumer, and Business | Card-Based and No Loan Fees [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	10,162	8,829	19,691	16,973
Community, Consumer, and Business | Fiduciary and Trust [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	13,437	12,346	26,806	24,281
Community, Consumer, and Business | Brokerage commissions and fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	6,870	4,346	13,902	8,679
Community, Consumer, and Business | Other revenue
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	2,302	2,196	4,763	4,315
Risk Management and Shared Services
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	156	81	490	165
Noninterest Income (out-of-scope of Topic 606)	2,242	4,022	5,570	6,906
Risk Management and Shared Services | Insurance commissions and fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	7	0	32	0
Risk Management and Shared Services | Deposit Account [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	13	23	25	49
Risk Management and Shared Services | Card-Based and No Loan Fees [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	42	5	67	11
Risk Management and Shared Services | Fiduciary and Trust [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	0	0	0	0
Risk Management and Shared Services | Brokerage commissions and fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	26	0	267	0
Risk Management and Shared Services | Other revenue
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	$ 68	$ 53	$ 98	$ 105