Allowance for Loan Losses - Loan Portfolio and Related Allowance (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Recorded Investment
Individually Evaluated for Impairment	$ 36,700	$ 30,291
Collectively Evaluated for Impairment	29,695	24,720
Total	4,810,780	3,799,961
Associated Allowance
Individually Evaluated for Impairment	2,728	2,402
Collectively Evaluated for Impairment	4,774,080	3,769,670
Total	32,423	27,122
PCI Loans
Recorded Investment
Individually Evaluated for Impairment	14,434	17,417
Associated Allowance
Individually Evaluated for Impairment	0	0
Real Estate \| Construction and land development
Recorded Investment
Individually Evaluated for Impairment	211	474
Collectively Evaluated for Impairment	2,211	1,619
Total	443,417	342,004
Associated Allowance
Individually Evaluated for Impairment	22	23
Collectively Evaluated for Impairment	443,206	341,530
Total	2,233	1,642
Real Estate \| Construction and land development \| PCI Loans
Recorded Investment
Individually Evaluated for Impairment	151	1,121
Associated Allowance
Individually Evaluated for Impairment	0	0
Real Estate \| Commercial real estate
Recorded Investment
Individually Evaluated for Impairment	13,638	8,255
Collectively Evaluated for Impairment	10,743	9,090
Total	2,121,238	1,630,215
Associated Allowance
Individually Evaluated for Impairment	369	195
Collectively Evaluated for Impairment	2,107,600	1,621,960
Total	11,112	9,285
Real Estate \| Commercial real estate \| PCI Loans
Recorded Investment
Individually Evaluated for Impairment	10,828	9,776
Associated Allowance
Individually Evaluated for Impairment	0	0
Real Estate \| Residential real estate
Recorded Investment
Individually Evaluated for Impairment	19,047	18,720
Collectively Evaluated for Impairment	6,970	6,040
Total	1,321,659	1,033,185
Associated Allowance
Individually Evaluated for Impairment	805	1,091
Collectively Evaluated for Impairment	1,302,612	1,014,465
Total	7,775	7,131
Real Estate \| Residential real estate \| PCI Loans
Recorded Investment
Individually Evaluated for Impairment	2,718	5,626
Associated Allowance
Individually Evaluated for Impairment	0	0
Commercial and financial \| Commercial and financial
Recorded Investment
Individually Evaluated for Impairment	3,322	2,455
Collectively Evaluated for Impairment	7,087	6,247
Total	721,585	605,121
Associated Allowance
Individually Evaluated for Impairment	1,498	1,050
Collectively Evaluated for Impairment	718,263	602,666
Total	8,585	7,297
Commercial and financial \| Commercial and financial \| PCI Loans
Recorded Investment
Individually Evaluated for Impairment	737	894
Associated Allowance
Individually Evaluated for Impairment	0	0
Consumer \| Consumer
Recorded Investment
Individually Evaluated for Impairment	482	387
Collectively Evaluated for Impairment	2,684	1,724
Total	202,881	189,436
Associated Allowance
Individually Evaluated for Impairment	34	43
Collectively Evaluated for Impairment	202,399	189,049
Total	2,718	1,767
Consumer \| Consumer \| PCI Loans
Recorded Investment
Individually Evaluated for Impairment	0	0
Associated Allowance
Individually Evaluated for Impairment	$ 0	$ 0

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A valuation allowance for financing receivables that are expected to be uncollectible.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
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The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524

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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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The balance of financing receivables that were collectively evaluated for impairment.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
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The balance of financing receivables that were individually evaluated for impairment.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
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Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
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-URI http://asc.fasb.org/extlink&oid=82891408&loc=d3e4428-111522

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