Revenues (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	$ 72,725	$ 64,881
Noninterest Income (out-of-scope of Topic 606)	17,655	14,950
Total noninterest income	90,380	79,831
Insurance commissions and fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	22,648	21,620
Service charges and deposit account fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	16,420	16,356
Card-based and loan fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	9,869	8,421
Trust and asset management fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	13,369	11,935
Brokerage commissions and fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	7,273	4,333
Other revenue
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	3,146	2,216
Corporate and Commercial Specialty
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	5,195	4,757
Noninterest Income (out-of-scope of Topic 606)	7,488	7,236
Total noninterest income	12,683	11,993
Corporate and Commercial Specialty | Insurance commissions and fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	0	0
Corporate and Commercial Specialty | Service charges and deposit account fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	4,225	4,441
Corporate and Commercial Specialty | Card-based and loan fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	315	272
Corporate and Commercial Specialty | Trust and asset management fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	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
Corporate and Commercial Specialty | Other revenue
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	655	44
Community, Consumer, and Business
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	67,198	60,040
Noninterest Income (out-of-scope of Topic 606)	6,838	4,830
Total noninterest income	74,036	64,870
Community, Consumer, and Business | Insurance commissions and fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	22,624	21,620
Community, Consumer, and Business | Service charges and deposit account fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	12,183	11,889
Community, Consumer, and Business | Card-based and loan fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	9,529	8,144
Community, Consumer, and Business | Trust and asset management fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	13,369	11,935
Community, Consumer, and Business | Brokerage commissions and fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	7,032	4,333
Community, Consumer, and Business | Other revenue
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	2,461	2,119
Risk Management and Shared Services
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	332	84
Noninterest Income (out-of-scope of Topic 606)	3,329	2,884
Total noninterest income	3,661	2,968
Risk Management and Shared Services | Insurance commissions and fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	24	0
Risk Management and Shared Services | Service charges and deposit account fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	12	26
Risk Management and Shared Services | Card-based and loan fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	25	5
Risk Management and Shared Services | Trust and asset management fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	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)	241	0
Risk Management and Shared Services | Other revenue
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income (in-scope of Topic 606)	$ 30	$ 53