Loans and Allowance for Loan Losses - Credit Quality Indicators by Portfolio Class (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	$ 3,078,076	$ 1,832,726
Purchased credit impaired loans	88,835	16,058	$ 21,375
Total loans	3,166,911	1,848,784	1,701,863
Pass
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	2,940,174	1,744,392
Total loans	2,940,174	1,744,392
Watch
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	114,401	65,807
Purchased credit impaired loans	56,848
Total loans	171,249	65,807
Substandard
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	23,501	22,527
Purchased credit impaired loans	31,987	16,058
Total loans	55,488	38,585
Commercial and Industrial
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	712,931	385,755
Purchased credit impaired loans	2,144	478	874
Total loans	715,075	386,233	318,791
Commercial and Industrial | Pass
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	657,595	351,046
Commercial and Industrial | Watch
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	50,946	31,074
Purchased credit impaired loans	1,499
Commercial and Industrial | Substandard
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	4,390	3,635
Purchased credit impaired loans	645	478
Construction
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	440,598	241,586
Purchased credit impaired loans	7,728	4,319	6,859
Total loans	448,326	245,905	238,170
Construction | Pass
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	431,242	236,588
Construction | Watch
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	7,388	4,612
Purchased credit impaired loans	3,324
Construction | Substandard
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	1,968	386
Purchased credit impaired loans	4,404	4,319
Residential Real Estate | 1-to-4 Family Mortgage
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	457,491	292,817
Purchased credit impaired loans	23,498	2,107	2,828
Total loans	480,989	294,924	290,704
Residential Real Estate | Residential Line of Credit
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	194,986	177,190
Total loans	194,986	177,190	171,526
Residential Real Estate | Multi-Family Mortgage
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	62,354	44,949
Purchased credit impaired loans	20	28	36
Total loans	62,374	44,977	59,510
Residential Real Estate | Pass | 1-to-4 Family Mortgage
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	440,202	277,948
Residential Real Estate | Pass | Residential Line of Credit
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	192,427	173,011
Residential Real Estate | Pass | Multi-Family Mortgage
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	61,234	43,770
Residential Real Estate | Watch | 1-to-4 Family Mortgage
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	9,522	6,945
Purchased credit impaired loans	20,284
Residential Real Estate | Watch | Residential Line of Credit
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	1,184	1,875
Residential Real Estate | Watch | Multi-Family Mortgage
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	142	152
Residential Real Estate | Substandard | 1-to-4 Family Mortgage
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	7,767	7,924
Purchased credit impaired loans	3,214	2,107
Residential Real Estate | Substandard | Residential Line of Credit
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	1,375	2,304
Residential Real Estate | Substandard | Multi-Family Mortgage
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	978	1,027
Purchased credit impaired loans	20	28
Commercial Real Estate | Owner Occupied
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	483,910	353,564
Purchased credit impaired loans	11,962	3,782	5,095
Total loans	495,872	357,346	337,664
Commercial Real Estate | Non-Owner Occupied
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	533,424	262,562
Purchased credit impaired loans	18,164	5,340	5,679
Total loans	551,588	267,902	207,871
Commercial Real Estate | Pass | Owner Occupied
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	451,140	338,698
Commercial Real Estate | Pass | Non-Owner Occupied
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	517,253	249,877
Commercial Real Estate | Watch | Owner Occupied
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	28,308	10,459
Purchased credit impaired loans	4,631
Commercial Real Estate | Watch | Non-Owner Occupied
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	14,199	10,273
Purchased credit impaired loans	7,359
Commercial Real Estate | Substandard | Owner Occupied
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	4,462	4,407
Purchased credit impaired loans	7,331	3,782
Commercial Real Estate | Substandard | Non-Owner Occupied
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	1,972	2,412
Purchased credit impaired loans	10,805	5,340
Consumer and Other
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	192,382	74,303
Purchased credit impaired loans	25,319	4	4
Total loans	217,701	74,307	$ 77,627
Consumer and Other | Pass
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	189,081	73,454
Consumer and Other | Watch
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	2,712	417
Purchased credit impaired loans	19,751
Consumer and Other | Substandard
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	589	432
Purchased credit impaired loans	$ 5,568	$ 4