Loans Receivable, Net - Credit Grades and Risk Characteristics (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
2020	$ 1,284,492
2019	1,377,097
2018	879,782
2017	841,628
2016	688,999
2015 and prior	2,562,378
Revolving lines of credit	366,602
Total	8,000,978	$ 6,214,652
Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
2020	238,681
2019	49,506
2018	34,717
2017	26,564
2016	39,298
2015 and prior	74,145
Revolving lines of credit	136,277
Total	599,188
Commercial and industrial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	238,326
2019	47,785
2018	32,607
2017	23,576
2016	38,353
2015 and prior	70,681
Revolving lines of credit	123,071
Total	574,399
Commercial and industrial | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	629
2018	759
2017	1,431
2016	892
2015 and prior	200
Revolving lines of credit	2,597
Total	6,508
Commercial and industrial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	355
2019	1,092
2018	1,351
2017	1,557
2016	53
2015 and prior	3,264
Revolving lines of credit	10,609
Total	18,281
Commercial real estate – owner occupied
Financing Receivable, Credit Quality Indicator [Line Items]
2020	78,646
2019	160,876
2018	147,145
2017	141,260
2016	129,100
2015 and prior	507,524
Revolving lines of credit	11,978
Total	1,176,529
Commercial real estate – owner occupied | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	78,646
2019	125,479
2018	132,958
2017	136,186
2016	117,713
2015 and prior	466,072
Revolving lines of credit	10,742
Total	1,067,796
Commercial real estate – owner occupied | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	1,736
2018	8,263
2017	1,374
2016	5,440
2015 and prior	15,477
Revolving lines of credit	393
Total	32,683
Commercial real estate – owner occupied | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	33,661
2018	5,924
2017	3,700
2016	5,947
2015 and prior	25,975
Revolving lines of credit	843
Total	76,050
Commercial real estate – investor
Financing Receivable, Credit Quality Indicator [Line Items]
2020	483,779
2019	647,497
2018	333,460
2017	458,517
2016	341,330
2015 and prior	975,349
Revolving lines of credit	213,344
Total	3,453,276
Commercial real estate – investor | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	479,468
2019	632,528
2018	309,128
2017	437,510
2016	323,544
2015 and prior	894,433
Revolving lines of credit	209,485
Total	3,286,096
Commercial real estate – investor | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	7,296
2018	22,274
2017	9,756
2016	9,657
2015 and prior	48,393
Revolving lines of credit	150
Total	97,526
Commercial real estate – investor | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	4,311
2019	7,673
2018	2,058
2017	11,251
2016	8,129
2015 and prior	32,523
Revolving lines of credit	3,709
Total	69,654
Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Total	2,771,985	2,729,155
Consumer | Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2020	464,585
2019	489,832
2018	269,891
2017	186,729
2016	161,255
2015 and prior	834,886
Revolving lines of credit	0
Total	2,407,178	$ 2,321,157
Consumer | Home Equity Lines and Other Consumer Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	18,801
2019	29,386
2018	94,569
2017	28,558
2016	18,016
2015 and prior	170,474
Revolving lines of credit	5,003
Total	364,807
Consumer | Pass | Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2020	464,423
2019	489,832
2018	268,996
2017	185,249
2016	161,255
2015 and prior	825,373
Revolving lines of credit	0
Total	2,395,128
Consumer | Pass | Home Equity Lines and Other Consumer Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	18,711
2019	28,994
2018	94,536
2017	28,558
2016	17,947
2015 and prior	166,364
Revolving lines of credit	5,003
Total	360,113
Consumer | Special Mention | Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2020	162
2019	0
2018	0
2017	1,112
2016	0
2015 and prior	2,891
Revolving lines of credit	0
Total	4,165
Consumer | Special Mention | Home Equity Lines and Other Consumer Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	90
2019	167
2018	0
2017	0
2016	0
2015 and prior	328
Revolving lines of credit	0
Total	585
Consumer | Substandard | Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	895
2017	368
2016	0
2015 and prior	6,622
Revolving lines of credit	0
Total	7,885
Consumer | Substandard | Home Equity Lines and Other Consumer Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	225
2018	33
2017	0
2016	69
2015 and prior	3,782
Revolving lines of credit	0
Total	$ 4,109