Allowance for Loan Losses - Recorded Investment Segregated by Amounts Individually or Collectively in Allowance for Loan Losses (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance, end of period	$ 1,081,873	$ 1,043,371
Balance, end of period: Individually evaluated for impairment	24,420	24,673
Balance, end of period: Collectively evaluated for impairment	1,057,453	1,018,698
Commercial
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance, end of period	433,388	411,327
Balance, end of period: Individually evaluated for impairment	14,553	16,077
Balance, end of period: Collectively evaluated for impairment	418,835	395,250
Real estate construction one-to-four family
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance, end of period	36,130	38,503
Balance, end of period: Individually evaluated for impairment	915	1,349
Balance, end of period: Collectively evaluated for impairment	35,215	37,154
Real estate construction other
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance, end of period	72,725	60,906
Balance, end of period: Individually evaluated for impairment	0	0
Balance, end of period: Collectively evaluated for impairment	72,725	60,906
Real estate term owner occupied
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance, end of period	145,693	138,181
Balance, end of period: Individually evaluated for impairment	6,840	5,104
Balance, end of period: Collectively evaluated for impairment	138,853	133,077
Real estate term non-owner occupied
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance, end of period	311,869	311,302
Balance, end of period: Individually evaluated for impairment	177	178
Balance, end of period: Collectively evaluated for impairment	311,692	311,124
Real estate term other
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance, end of period	41,980	42,200
Balance, end of period: Individually evaluated for impairment	1,573	1,594
Balance, end of period: Collectively evaluated for impairment	40,407	40,606
Consumer secured by 1st deeds of trust
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance, end of period	15,562	16,191
Balance, end of period: Individually evaluated for impairment	275	281
Balance, end of period: Collectively evaluated for impairment	15,287	15,910
Consumer other
Financing Receivable, Allowance for Credit Loss [Line Items]
Balance, end of period	24,526	24,761
Balance, end of period: Individually evaluated for impairment	87	90
Balance, end of period: Collectively evaluated for impairment	$ 24,439	$ 24,671