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Summary of Significant Accounting Policies - Impact of ASU 2016-13 (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Jan. 01, 2020	Dec. 31, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance	$ 7,225,860		$ 7,137,152
Allowance for credit losses on loans	(117,612)	$ (62,224)	(62,224)	$ (60,996)
Total loans	7,108,248	7,074,928	7,074,928
Net deferred tax asset	18,193	13,206	13,206
Allowance for credit losses on unfunded loan commitments	4,467	3,113	3,112	2,139
Retained earnings	710,061	761,083	761,083
As Reported Under ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans		(89,577)
Total loans		7,047,575
Net deferred tax asset		19,317
Allowance for credit losses on unfunded loan commitments		4,462	4,461	2,139
Retained earnings		738,493
Impact of ASU 2016-13 Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans		(27,353)	(27,346)
Total loans		(27,353)
Net deferred tax asset		6,111
Allowance for credit losses on unfunded loan commitments		1,349	1,349	0
Retained earnings		(22,590)
Commercial
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance	5,977,643		5,756,971
Commercial \| Commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance	2,791,947	3,416,518	3,059,592
Allowance for credit losses on loans	(65,656)		(30,577)	(33,707)
Commercial \| Commercial real estate \| As Reported Under ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance		2,946,319
Commercial \| Commercial real estate \| Impact of ASU 2016-13 Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance		(470,199)
Allowance for credit losses on loans			(4,810)
Commercial \| Commercial and industrial
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance	1,559,552	1,720,833	1,480,529
Allowance for credit losses on loans	(16,100)		(15,681)	(11,596)
Commercial \| Commercial and industrial \| As Reported Under ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance		1,458,541
Commercial \| Commercial and industrial \| Impact of ASU 2016-13 Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance		(262,292)
Allowance for credit losses on loans		(9,900)	(7,853)
Commercial \| Commercial construction
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance	466,077	375,445	370,060
Allowance for credit losses on loans	(7,239)		(7,900)	(7,983)
Commercial \| Commercial construction \| As Reported Under ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance		345,263
Commercial \| Commercial construction \| Impact of ASU 2016-13 Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance		(30,182)
Allowance for credit losses on loans			3,376
Commercial \| Business banking
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance	1,160,067	0	846,790
Allowance for credit losses on loans	(15,917)		0
Commercial \| Business banking \| As Reported Under ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance		1,092,908
Commercial \| Business banking \| Impact of ASU 2016-13 Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance		1,092,908
Allowance for credit losses on loans			(12,898)
Consumer
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance	1,248,217		1,380,181
Consumer \| Commercial construction
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance			8,390
Consumer \| Consumer real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance	1,167,332	1,545,323	1,295,207
Allowance for credit losses on loans	(10,014)		(6,337)	(6,187)
Consumer \| Consumer real estate \| As Reported Under ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance		1,235,352
Consumer \| Consumer real estate \| Impact of ASU 2016-13 Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance		(309,971)
Allowance for credit losses on loans			(4,525)
Consumer \| Other consumer
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance	80,885	79,033	84,974
Allowance for credit losses on loans	$ (2,686)		(1,729)	$ (1,523)
Consumer \| Other consumer \| As Reported Under ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance		58,769
Consumer \| Other consumer \| Impact of ASU 2016-13 Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loans held for investment, outstanding balance		$ (20,264)
Allowance for credit losses on loans			$ (636)