Loans and Leases - Reserve for Loan and Lease Losses and Recorded Investment in Loans and Leases (Details) - USD ($) $ in Thousands		Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Reserve for loan and lease losses:
Ending balance: individually evaluated for impairment		$ 2,439			$ 1,524
Ending balance: collectively evaluated for impairment		30,153			24,046
Ending balance: acquired non-credit impaired loans evaluated for impairment		8			82
Total ending balance		32,600	$ 31,602	$ 29,364	25,652	$ 23,410	$ 21,555
Loans and leases held for investment:
Ending balance: individually evaluated for impairment (1)	[1]	25,102			33,930
Ending balance: collectively evaluated for impairment		3,823,002			3,344,062
Loans measured at fair value		1,725			1,847
Acquired non-credit impaired loans		317,506			437,561
Acquired credit impaired loans		569			998
Total Loans and Leases Held for Investment		4,167,904		4,006,574	3,818,398
Commercial, Financial and Agricultural [Member]
Reserve for loan and lease losses:
Ending balance: individually evaluated for impairment		99			646
Ending balance: collectively evaluated for impairment		9,030			6,612
Ending balance: acquired non-credit impaired loans evaluated for impairment		0			0
Total ending balance		9,129	8,950	7,983	7,258	6,942	6,742
Loans and leases held for investment:
Ending balance: individually evaluated for impairment (1)	[1]	2,150			6,238
Ending balance: collectively evaluated for impairment		919,032			875,390
Loans measured at fair value		0			0
Acquired non-credit impaired loans		15,967			44,265
Acquired credit impaired loans		0			267
Total Loans and Leases Held for Investment		937,149		937,685	926,160
Real Estate-Commercial and Construction [Member]
Reserve for loan and lease losses:
Ending balance: individually evaluated for impairment		1,840			866
Ending balance: collectively evaluated for impairment		13,630			11,420
Ending balance: acquired non-credit impaired loans evaluated for impairment		8			41
Total ending balance		15,478	14,981	13,903	12,327	11,178	9,839
Loans and leases held for investment:
Ending balance: individually evaluated for impairment (1)	[1]	17,845			21,004
Ending balance: collectively evaluated for impairment		1,873,296			1,569,475
Loans measured at fair value		1,725			1,847
Acquired non-credit impaired loans		199,534			259,998
Acquired credit impaired loans		206			206
Total Loans and Leases Held for Investment		2,092,606			1,852,530
Real Estate-Residential Secured for Business Purpose [Member]
Reserve for loan and lease losses:
Ending balance: individually evaluated for impairment		165			12
Ending balance: collectively evaluated for impairment		2,313			1,951
Ending balance: acquired non-credit impaired loans evaluated for impairment		0			41
Total ending balance		2,478	2,302	2,236	2,004	1,871	1,661
Loans and leases held for investment:
Ending balance: individually evaluated for impairment (1)	[1]	1,596			2,132
Ending balance: collectively evaluated for impairment		313,291			265,283
Loans measured at fair value		0			0
Acquired non-credit impaired loans		50,451			70,837
Acquired credit impaired loans		302			460
Total Loans and Leases Held for Investment		365,640		362,796	338,712
Real Estate-Residential and Home Equity Secured for Personal Purpose [Member]
Reserve for loan and lease losses:
Ending balance: individually evaluated for impairment		335			0
Ending balance: collectively evaluated for impairment		3,183			2,494
Ending balance: acquired non-credit impaired loans evaluated for impairment		0			0
Total ending balance		3,518	3,379	3,199	2,494	1,908	1,754
Loans and leases held for investment:
Ending balance: individually evaluated for impairment (1)	[1]	3,511			3,306
Ending balance: collectively evaluated for impairment		542,751			470,994
Loans measured at fair value		0			0
Acquired non-credit impaired loans		51,414			62,318
Acquired credit impaired loans		61			65
Total Loans and Leases Held for Investment		597,737			536,683
Loans to Individuals [Member]
Reserve for loan and lease losses:
Ending balance: individually evaluated for impairment		0			0
Ending balance: collectively evaluated for impairment		481			447
Ending balance: acquired non-credit impaired loans evaluated for impairment		0			0
Total ending balance		481	469	484	447	372	373
Loans and leases held for investment:
Ending balance: individually evaluated for impairment (1)	[1]	0			0
Ending balance: collectively evaluated for impairment		32,345			31,048
Loans measured at fair value		0			0
Acquired non-credit impaired loans		140			143
Acquired credit impaired loans		0			0
Total Loans and Leases Held for Investment		32,485		32,759	31,191
Lease Financings [Member]
Reserve for loan and lease losses:
Ending balance: individually evaluated for impairment		0			0
Ending balance: collectively evaluated for impairment		1,241			1,071
Ending balance: acquired non-credit impaired loans evaluated for impairment		0			0
Total ending balance		1,241	1,275	1,288	1,071	1,079	1,132
Loans and leases held for investment:
Ending balance: individually evaluated for impairment (1)	[1]	0			1,250
Ending balance: collectively evaluated for impairment		142,287			131,872
Loans measured at fair value		0			0
Acquired non-credit impaired loans		0			0
Acquired credit impaired loans		0			0
Total Loans and Leases Held for Investment		142,287		141,956	133,122
Unallocated Financing Receivables [Member]
Reserve for loan and lease losses:
Ending balance: collectively evaluated for impairment		275			51
Ending balance: acquired non-credit impaired loans evaluated for impairment		0			0
Total ending balance		$ 275	$ 246	$ 271	$ 51	$ 60	$ 54

[1] (1) Includes $14.6 million and $17.9 million of acquired loans which were individually evaluated for impairment at June 30, 2019 and 2018, respectively.