Loans and the Allowance for Loan Losses (Details) - Credit quality indicators - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	$ 4,174,810	$ 3,479,441
Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	4,045,989	3,405,931
Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	43,620	37,816
Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	85,201	35,694
Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount
Commercial Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	824,082	553,576
Commercial Portfolio Segment [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	767,020	539,961
Commercial Portfolio Segment [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	3,764	3,255
Commercial Portfolio Segment [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	53,298	10,360
Commercial Portfolio Segment [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	2,592,909	2,204,710
Commercial Real Estate Portfolio Segment [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	2,534,973	2,154,343
Commercial Real Estate Portfolio Segment [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	34,335	31,173
Commercial Real Estate Portfolio Segment [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	23,601	19,194
Commercial Real Estate Portfolio Segment [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount
Construction Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	483,216	486,228
Construction Loans [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	475,066	480,319
Construction Loans [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	5,521	3,388
Construction Loans [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	2,629	2,521
Construction Loans [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount
Residential Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	271,795	232,547
Residential Portfolio Segment [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	266,163	228,990
Residential Portfolio Segment [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount
Residential Portfolio Segment [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	5,632	3,557
Residential Portfolio Segment [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount
Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	2,808	2,380
Consumer Portfolio Segment [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	2,767	2,318
Consumer Portfolio Segment [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount
Consumer Portfolio Segment [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	41	62
Consumer Portfolio Segment [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount