Loans and Allowance for Loan Losses - Activity in the Allowance for Loan Losses, by Portfolio Segment, for the Current Year (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	$ 47,614	$ 38,300	$ 42,086	$ 37,240
Provision for loan losses	9,033	7,023	18,183	11,330
Balance, end of year	53,776	41,770	53,776	41,770
Loans, Excluding Acquired Loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	47,207	37,865	41,668	36,286
Provision for loan losses	7,264	6,308	16,346	9,865
Charge-offs	(3,329)	(3,955)	(7,600)	(7,121)
Recoveries	590	1,161	1,318	2,349
Net charge-offs	(2,739)	(2,794)	(6,282)	(4,772)
Balance, end of year	51,732	41,379	51,732	41,379
Period-end amount allocated to:
Loans individually evaluated for impairment	445	5,524	445	5,524	$ 338
Loans collectively evaluated for impairment	51,287	35,855	51,287	35,855	41,330
Loans, Excluding Acquired Loans | Other Consumer and Other
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	3,393	3,710	3,596	2,951
Provision for loan losses	1,079	436	1,838	1,679
Charge-offs	(1,366)	(993)	(2,422)	(2,167)
Recoveries	133	636	227	1,326
Net charge-offs	(1,233)	(357)	(2,195)	(841)
Balance, end of year	3,239	3,789	3,239	3,789
Period-end amount allocated to:
Loans individually evaluated for impairment	0	0	0	0	0
Loans collectively evaluated for impairment	3,239	3,789	3,239	3,789	3,596
Loans, Excluding Acquired Loans | Commercial
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	9,601	8,173	7,007	7,739
Provision for loan losses	6,897	249	11,183	945
Charge-offs	(790)	(349)	(2,551)	(641)
Recoveries	59	32	128	62
Net charge-offs	(731)	(317)	(2,423)	(579)
Balance, end of year	15,767	8,105	15,767	8,105
Period-end amount allocated to:
Loans individually evaluated for impairment	18	3,636	18	3,636	0
Loans collectively evaluated for impairment	15,749	4,469	15,749	4,469	7,007
Loans, Excluding Acquired Loans | Real estate
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	30,414	22,253	27,281	21,817
Provision for loan losses	(1,461)	4,974	1,825	5,834
Charge-offs	(161)	(1,712)	(616)	(2,368)
Recoveries	112	216	414	448
Net charge-offs	(49)	(1,496)	(202)	(1,920)
Balance, end of year	28,904	25,731	28,904	25,731
Period-end amount allocated to:
Loans individually evaluated for impairment	427	1,888	427	1,888	338
Loans collectively evaluated for impairment	28,477	23,843	28,477	23,843	26,943
Loans, Excluding Acquired Loans | Consumer | Credit cards
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	3,799	3,729	3,784	3,779
Provision for loan losses	749	649	1,500	1,407
Charge-offs	(1,012)	(901)	(2,011)	(1,945)
Recoveries	286	277	549	513
Net charge-offs	(726)	(624)	(1,462)	(1,432)
Balance, end of year	3,822	3,754	3,822	3,754
Period-end amount allocated to:
Loans individually evaluated for impairment	0	0	0	0	0
Loans collectively evaluated for impairment	3,822	3,754	3,822	3,754	$ 3,784
Loans Acquired
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	407	435	418	954
Provision for loan losses	1,769	714	1,837	1,464
Charge-offs	(132)	(758)	(211)	(2,000)
Balance, end of year	$ 2,044	$ 391	$ 2,044	$ 391