Loans - Consumer Loans by Risk Rating Categories (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 13,667,372	$ 12,990,779
Originated
Financing Receivable, Recorded Investment [Line Items]
Total loans	8,659,622	7,458,401
Originated | Residential mortgage
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,683,550	1,475,342
Originated | Consumer installment
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,429,088	1,282,588
Originated | Home equity
Financing Receivable, Recorded Investment [Line Items]
Total loans	607,534	595,422
Acquired
Financing Receivable, Recorded Investment [Line Items]
Total loans	5,007,750	5,532,378
Consumer loan portfolio
Financing Receivable, Recorded Investment [Line Items]
Total loans	5,536,210	5,396,567
Consumer loan portfolio | Residential mortgage
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,125,397	3,086,474
Consumer loan portfolio | Consumer installment
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,553,967	1,433,884
Consumer loan portfolio | Home equity
Financing Receivable, Recorded Investment [Line Items]
Total loans	856,846	876,209
Consumer loan portfolio | Originated
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,720,172	3,353,352
Consumer loan portfolio | Originated | Residential mortgage
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,683,550	1,475,342
Consumer loan portfolio | Originated | Consumer installment
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,429,088	1,282,588
Consumer loan portfolio | Originated | Home equity
Financing Receivable, Recorded Investment [Line Items]
Total loans	607,534	595,422
Consumer loan portfolio | Originated | Performing
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,707,830	3,342,153
Consumer loan portfolio | Originated | Performing | Residential mortgage
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,675,836	1,468,373
Consumer loan portfolio | Originated | Performing | Consumer installment
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,428,331	1,281,709
Consumer loan portfolio | Originated | Performing | Home equity
Financing Receivable, Recorded Investment [Line Items]
Total loans	603,663	592,071
Consumer loan portfolio | Originated | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Total loans	12,342	11,199
Consumer loan portfolio | Originated | Nonperforming | Residential mortgage
Financing Receivable, Recorded Investment [Line Items]
Total loans	7,714	6,969
Consumer loan portfolio | Originated | Nonperforming | Consumer installment
Financing Receivable, Recorded Investment [Line Items]
Total loans	757	879
Consumer loan portfolio | Originated | Nonperforming | Home equity
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,871	3,351
Consumer loan portfolio | Acquired
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,816,038	2,043,215
Consumer loan portfolio | Acquired | Residential mortgage
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,441,847	1,611,132
Consumer loan portfolio | Acquired | Consumer installment
Financing Receivable, Recorded Investment [Line Items]
Total loans	124,879	151,296
Consumer loan portfolio | Acquired | Home equity
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 249,312	$ 280,787