Allowance for Credit Losses and Credit Quality of Loans, Credit Quality Indicators (Details) $ in Thousands	Mar. 31, 2020 USD ($)
Credit Quality by Loan Class by Vintage [Abstract]
2020	$ 438,451
2019	1,579,255
2018	1,128,318
2017	945,231
2016	636,334
Prior	1,564,836
Revolving Loans Amortized Cost Basis	837,852
Revolving Loans Converted to Term	117,107
Total	7,247,383
C&I [Member]
Credit Quality by Loan Class by Vintage [Abstract]
2020	87,854
2019	252,083
2018	136,300
2017	70,858
2016	53,537
Prior	61,787
Revolving Loans Amortized Cost Basis	433,961
Revolving Loans Converted to Term	22,660
Total	1,119,040
C&I [Member] | Pass [Member]
Credit Quality by Loan Class by Vintage [Abstract]
2020	87,313
2019	245,200
2018	121,720
2017	63,276
2016	49,619
Prior	49,841
Revolving Loans Amortized Cost Basis	408,302
Revolving Loans Converted to Term	22,633
Total	1,047,904
C&I [Member] | Special Mention [Member]
Credit Quality by Loan Class by Vintage [Abstract]
2020	0
2019	4,881
2018	3,654
2017	3,286
2016	3,299
Prior	2,379
Revolving Loans Amortized Cost Basis	18,803
Revolving Loans Converted to Term	0
Total	36,302
C&I [Member] | Substandard [Member]
Credit Quality by Loan Class by Vintage [Abstract]
2020	541
2019	2,002
2018	10,926
2017	3,317
2016	619
Prior	6,168
Revolving Loans Amortized Cost Basis	6,856
Revolving Loans Converted to Term	27
Total	30,456
C&I [Member] | Doubtful [Member]
Credit Quality by Loan Class by Vintage [Abstract]
2020	0
2019	0
2018	0
2017	979
2016	0
Prior	3,399
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term	0
Total	4,378
CRE [Member]
Credit Quality by Loan Class by Vintage [Abstract]
2020	131,293
2019	460,984
2018	302,072
2017	399,152
2016	281,037
Prior	625,728
Revolving Loans Amortized Cost Basis	108,621
Revolving Loans Converted to Term	32,923
Total	2,341,810
CRE [Member] | Pass [Member]
Credit Quality by Loan Class by Vintage [Abstract]
2020	130,895
2019	458,228
2018	288,204
2017	392,223
2016	275,496
Prior	551,128
Revolving Loans Amortized Cost Basis	98,679
Revolving Loans Converted to Term	24,003
Total	2,218,856
CRE [Member] | Special Mention [Member]
Credit Quality by Loan Class by Vintage [Abstract]
2020	398
2019	2,635
2018	7,427
2017	3,493
2016	1,745
Prior	35,625
Revolving Loans Amortized Cost Basis	675
Revolving Loans Converted to Term	8,920
Total	60,918
CRE [Member] | Substandard [Member]
Credit Quality by Loan Class by Vintage [Abstract]
2020	0
2019	121
2018	6,441
2017	3,436
2016	3,796
Prior	38,975
Revolving Loans Amortized Cost Basis	9,267
Revolving Loans Converted to Term	0
Total	62,036
Auto [Member]
Credit Quality by Loan Class by Vintage [Abstract]
2020	112,458
2019	412,727
2018	292,299
2017	196,996
2016	92,993
Prior	43,544
Revolving Loans Amortized Cost Basis	25
Revolving Loans Converted to Term	0
Total	1,151,042
Auto [Member] | Performing [Member]
Credit Quality by Loan Class by Vintage [Abstract]
2020	112,417
2019	411,824
2018	291,092
2017	196,440
2016	92,378
Prior	43,534
Revolving Loans Amortized Cost Basis	25
Revolving Loans Converted to Term	0
Total	1,147,710
Auto [Member] | Nonperforming [Member]
Credit Quality by Loan Class by Vintage [Abstract]
2020	41
2019	903
2018	1,207
2017	556
2016	615
Prior	10
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term	0
Total	3,332
Other Consumer [Member]
Credit Quality by Loan Class by Vintage [Abstract]
2020	67,233
2019	229,455
2018	171,293
2017	79,919
2016	26,195
Prior	26,339
Revolving Loans Amortized Cost Basis	22,463
Revolving Loans Converted to Term	12
Total	622,908
Other Consumer [Member] | Performing [Member]
Credit Quality by Loan Class by Vintage [Abstract]
2020	67,233
2019	229,068
2018	170,909
2017	79,635
2016	26,131
Prior	26,202
Revolving Loans Amortized Cost Basis	22,450
Revolving Loans Converted to Term	10
Total	621,638
Other Consumer [Member] | Nonperforming [Member]
Credit Quality by Loan Class by Vintage [Abstract]
2020	0
2019	387
2018	384
2017	284
2016	64
Prior	137
Revolving Loans Amortized Cost Basis	13
Revolving Loans Converted to Term	2
Total	1,270
Residential [Member]
Credit Quality by Loan Class by Vintage [Abstract]
2020	39,613
2019	224,006
2018	226,354
2017	198,306
2016	182,572
Prior	807,438
Revolving Loans Amortized Cost Basis	272,782
Revolving Loans Converted to Term	61,512
Total	2,012,583
Residential [Member] | Performing [Member]
Credit Quality by Loan Class by Vintage [Abstract]
2020	39,592
2019	223,715
2018	225,817
2017	196,901
2016	182,269
Prior	798,850
Revolving Loans Amortized Cost Basis	272,782
Revolving Loans Converted to Term	61,439
Total	2,001,365
Residential [Member] | Nonperforming [Member]
Credit Quality by Loan Class by Vintage [Abstract]
2020	21
2019	291
2018	537
2017	1,405
2016	303
Prior	8,588
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term	73
Total	$ 11,218