Loans and Allowance for Loan Losses - Activity in the Allowance for Loan Losses, by Portfolio Segment, for the Current Year (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	$ 53,776,000	$ 41,770,000	$ 42,086,000	$ 37,240,000
Provision for loan losses	10,345,000	5,462,000	28,528,000	16,792,000
Balance, end of year	56,703,000	43,108,000	56,703,000	43,108,000
Loans, Excluding Acquired Loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	51,732,000	41,379,000	41,668,000	36,286,000
Provision for loan losses	10,345,000	5,462,000	26,691,000	15,327,000
Charge-offs	(7,784,000)	(5,174,000)	(15,384,000)	(12,295,000)
Recoveries	1,065,000	1,050,000	2,383,000	3,399,000
Net charge-offs	(6,719,000)	(4,124,000)	(13,001,000)	(8,896,000)
Balance, end of year	55,358,000	42,717,000	55,358,000	42,717,000
Period-end amount allocated to:
Loans individually evaluated for impairment	459,000	6,321,000	459,000	6,321,000	$ 338,000
Loans collectively evaluated for impairment	54,899,000	36,396,000	54,899,000	36,396,000	41,330,000
Loans, Excluding Acquired Loans | Other Consumer and Other
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	3,239,000	3,789,000	3,596,000	2,951,000
Provision for loan losses	729,000	241,000	2,567,000	1,920,000
Charge-offs	(1,321,000)	(819,000)	(3,743,000)	(2,986,000)
Recoveries	176,000	445,000	403,000	1,771,000
Net charge-offs	(1,145,000)	(374,000)	(3,340,000)	(1,215,000)
Balance, end of year	2,823,000	3,656,000	2,823,000	3,656,000
Period-end amount allocated to:
Loans individually evaluated for impairment	0	0	0	0	0
Loans collectively evaluated for impairment	2,823,000	3,656,000	2,823,000	3,656,000	3,596,000
Loans, Excluding Acquired Loans | Commercial
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	15,767,000	8,105,000	7,007,000	7,739,000
Provision for loan losses	3,589,000	2,310,000	14,772,000	3,255,000
Charge-offs	(592,000)	(2,442,000)	(3,143,000)	(3,083,000)
Recoveries	450,000	21,000	578,000	83,000
Net charge-offs	(142,000)	(2,421,000)	(2,565,000)	(3,000,000)
Balance, end of year	19,214,000	7,994,000	19,214,000	7,994,000
Period-end amount allocated to:
Loans individually evaluated for impairment	191,000	3,996,000	191,000	3,996,000	0
Loans collectively evaluated for impairment	19,023,000	3,998,000	19,023,000	3,998,000	7,007,000
Loans, Excluding Acquired Loans | Real estate
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	28,904,000	25,731,000	27,281,000	21,817,000
Provision for loan losses	5,308,000	2,150,000	7,133,000	7,984,000
Charge-offs	(4,952,000)	(896,000)	(5,568,000)	(3,264,000)
Recoveries	210,000	309,000	624,000	757,000
Net charge-offs	(4,742,000)	(587,000)	(4,944,000)	(2,507,000)
Balance, end of year	29,470,000	27,294,000	29,470,000	27,294,000
Period-end amount allocated to:
Loans individually evaluated for impairment	268,000	2,325,000	268,000	2,325,000	338,000
Loans collectively evaluated for impairment	29,202,000	24,969,000	29,202,000	24,969,000	26,943,000
Loans, Excluding Acquired Loans | Consumer | Credit cards
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	3,822,000	3,754,000	3,784,000	3,779,000
Provision for loan losses	719,000	761,000	2,219,000	2,168,000
Charge-offs	(919,000)	(1,017,000)	(2,930,000)	(2,962,000)
Recoveries	229,000	275,000	778,000	788,000
Net charge-offs	(690,000)	(742,000)	(2,152,000)	(2,174,000)
Balance, end of year	3,851,000	3,773,000	3,851,000	3,773,000
Period-end amount allocated to:
Loans individually evaluated for impairment	0	0	0	0	0
Loans collectively evaluated for impairment	3,851,000	3,773,000	3,851,000	3,773,000	$ 3,784,000
Loans Acquired
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	2,044,000		418,000	954,000
Provision for loan losses	0	0	1,837,000	1,464,000
Charge-offs	(699,000)		(910,000)	(2,000,000)
Balance, end of year	$ 1,345,000	$ 391,000	$ 1,345,000	$ 391,000