Loans Receivable - Past Due Loans (Details) - USD ($)	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Past Due [Line Items]
Total Past Due	$ 14,113,000
Current	3,838,263,000
Loans and Leases Receivable, Net of Deferred Income	3,852,376,000	$ 3,767,879,000
Certain Loans and Debt Securities Acquired in Transfer, with Related Allowance for Credit Losses Due to Subsequent Impairment		18,110,000
90 days or more and still accruing	0
Financing Receivables, 30 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due	7,015,000
90 Days or Greater
Financing Receivable, Past Due [Line Items]
Total Past Due	7,098,000
Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due	11,684,000	21,061,000
Current	2,995,945,000	2,912,399,000
Loan and Lease Receivable, Gross excluding Purchase Credit Impaired Loans		2,933,460,000
Loans and Leases Receivable, Net of Deferred Income	3,007,629,000	2,946,233,000
Certain Loans and Debt Securities Acquired in Transfer, with Related Allowance for Credit Losses Due to Subsequent Impairment		12,773,000
Commercial Portfolio Segment [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due	4,605,000	11,640,000
Commercial Portfolio Segment [Member] | 90 Days or Greater
Financing Receivable, Past Due [Line Items]
Total Past Due	7,079,000	9,421,000
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due	9,221,000	17,251,000
Current	880,464,000	832,601,000
Loan and Lease Receivable, Gross excluding Purchase Credit Impaired Loans		849,852,000
Loans and Leases Receivable, Net of Deferred Income	889,685,000	852,220,000
Certain Loans and Debt Securities Acquired in Transfer, with Related Allowance for Credit Losses Due to Subsequent Impairment		2,368,000
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due	2,632,000	10,479,000
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member] | 90 Days or Greater
Financing Receivable, Past Due [Line Items]
Total Past Due	6,589,000	6,772,000
Commercial Portfolio Segment [Member] | Owner Occupied Commercial Real Estate [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due	843,000	1,413,000
Current	804,793,000	798,907,000
Loan and Lease Receivable, Gross excluding Purchase Credit Impaired Loans		800,320,000
Loans and Leases Receivable, Net of Deferred Income	805,636,000	805,234,000
Certain Loans and Debt Securities Acquired in Transfer, with Related Allowance for Credit Losses Due to Subsequent Impairment		4,914,000
Commercial Portfolio Segment [Member] | Owner Occupied Commercial Real Estate [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due	353,000	607,000
Commercial Portfolio Segment [Member] | Owner Occupied Commercial Real Estate [Member] | 90 Days or Greater
Financing Receivable, Past Due [Line Items]
Total Past Due	490,000	806,000
Commercial Portfolio Segment [Member] | Non Owner Occupied Commercial Real Estate [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due	1,620,000	2,397,000
Current	1,310,688,000	1,280,891,000
Loan and Lease Receivable, Gross excluding Purchase Credit Impaired Loans		1,283,288,000
Loans and Leases Receivable, Net of Deferred Income	1,312,308,000	1,288,779,000
Certain Loans and Debt Securities Acquired in Transfer, with Related Allowance for Credit Losses Due to Subsequent Impairment		5,491,000
Commercial Portfolio Segment [Member] | Non Owner Occupied Commercial Real Estate [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due	1,620,000	554,000
Commercial Portfolio Segment [Member] | Non Owner Occupied Commercial Real Estate [Member] | 90 Days or Greater
Financing Receivable, Past Due [Line Items]
Total Past Due	0	1,843,000
Residential Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due	466,000	797,000
Current	136,316,000	127,288,000
Loan and Lease Receivable, Gross excluding Purchase Credit Impaired Loans		128,085,000
Loans and Leases Receivable, Net of Deferred Income	136,782,000	131,660,000
Certain Loans and Debt Securities Acquired in Transfer, with Related Allowance for Credit Losses Due to Subsequent Impairment		3,575,000
Residential Portfolio Segment [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due	447,000	797,000
Residential Portfolio Segment [Member] | 90 Days or Greater
Financing Receivable, Past Due [Line Items]
Total Past Due	19,000	0
Real Estate Construction and Land Development
Financing Receivable, Past Due [Line Items]
Total Past Due	0	1,516,000
Current	287,034,000	273,130,000
Loan and Lease Receivable, Gross excluding Purchase Credit Impaired Loans		274,646,000
Loans and Leases Receivable, Net of Deferred Income	287,034,000	274,646,000
Certain Loans and Debt Securities Acquired in Transfer, with Related Allowance for Credit Losses Due to Subsequent Impairment		0
Real Estate Construction and Land Development | Financing Receivables, 30 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due	0	1,516,000
Real Estate Construction and Land Development | 90 Days or Greater
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Real Estate Construction and Land Development | One-to-four Family Real Estate Construction
Financing Receivable, Past Due [Line Items]
Total Past Due	0	1,516,000
Current	98,730,000	102,780,000
Loan and Lease Receivable, Gross excluding Purchase Credit Impaired Loans		104,296,000
Loans and Leases Receivable, Net of Deferred Income	98,730,000	104,296,000
Certain Loans and Debt Securities Acquired in Transfer, with Related Allowance for Credit Losses Due to Subsequent Impairment		0
Real Estate Construction and Land Development | One-to-four Family Real Estate Construction | Financing Receivables, 30 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due	0	1,516,000
Real Estate Construction and Land Development | One-to-four Family Real Estate Construction | 90 Days or Greater
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Real Estate Construction and Land Development | Five or More Family Residential and Commercial Properties [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Current	188,304,000	170,350,000
Loan and Lease Receivable, Gross excluding Purchase Credit Impaired Loans		170,350,000
Loans and Leases Receivable, Net of Deferred Income	188,304,000	170,350,000
Certain Loans and Debt Securities Acquired in Transfer, with Related Allowance for Credit Losses Due to Subsequent Impairment		0
Real Estate Construction and Land Development | Five or More Family Residential and Commercial Properties [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Real Estate Construction and Land Development | Five or More Family Residential and Commercial Properties [Member] | 90 Days or Greater
Financing Receivable, Past Due [Line Items]
Total Past Due	0	0
Consumer Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due	1,963,000	2,071,000
Current	418,968,000	411,507,000
Loan and Lease Receivable, Gross excluding Purchase Credit Impaired Loans		413,578,000
Loans and Leases Receivable, Net of Deferred Income	420,931,000	415,340,000
Certain Loans and Debt Securities Acquired in Transfer, with Related Allowance for Credit Losses Due to Subsequent Impairment		1,762,000
Consumer Portfolio Segment [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due	1,963,000	2,071,000
Consumer Portfolio Segment [Member] | 90 Days or Greater
Financing Receivable, Past Due [Line Items]
Total Past Due	$ 0	0
Loans Receivable Excluding PCI Loans [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due		25,445,000
Current		3,724,324,000
Loan and Lease Receivable, Gross excluding Purchase Credit Impaired Loans		3,749,769,000
Loans Receivable Excluding PCI Loans [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total Past Due		16,024,000
Loans Receivable Excluding PCI Loans [Member] | 90 Days or Greater
Financing Receivable, Past Due [Line Items]
Total Past Due		$ 9,421,000