Loans and Allowance for Loan Losses - Credit Quality Indicators by Portfolio Class (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	$ 3,022,107	$ 1,832,726
Purchased credit impaired loans	92,455	16,058
Gross loans	3,114,562	1,848,784
Pass
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	2,888,786	1,744,392
Gross loans	2,888,786	1,744,392
Watch
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	110,798	65,807
Purchased credit impaired loans	55,390
Gross loans	166,188	65,807
Substandard
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	22,523	22,527
Purchased credit impaired loans	37,065	16,058
Gross loans	59,588	38,585
Commercial and Industrial
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	728,711	385,755
Purchased credit impaired loans	2,877	478
Gross loans	731,588	386,233
Commercial and Industrial | Pass
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	671,566	351,046
Commercial and Industrial | Watch
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	53,388	31,074
Purchased credit impaired loans	1,665
Commercial and Industrial | Substandard
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	3,757	3,635
Purchased credit impaired loans	1,212	478
Construction
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	427,334	241,586
Purchased credit impaired loans	8,080	4,319
Gross loans	435,414	245,905
Construction | Pass
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	419,219	236,588
Construction | Watch
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	6,402	4,612
Purchased credit impaired loans	3,383
Construction | Substandard
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	1,713	386
Purchased credit impaired loans	4,697	4,319
Residential Real Estate | 1-to-4 Family Mortgage
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	434,816	292,817
Purchased credit impaired loans	24,651	2,107
Gross loans	459,467	294,924
Residential Real Estate | Residential Line of Credit
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	188,392	177,190
Gross loans	188,392	177,190
Residential Real Estate | Multi-Family Mortgage
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	73,982	44,949
Purchased credit impaired loans	22	28
Gross loans	74,004	44,977
Residential Real Estate | Pass | 1-to-4 Family Mortgage
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	421,020	277,948
Residential Real Estate | Pass | Residential Line of Credit
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	185,892	173,011
Residential Real Estate | Pass | Multi-Family Mortgage
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	72,214	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	6,548	6,945
Purchased credit impaired loans	21,127
Residential Real Estate | Watch | Residential Line of Credit
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	1,461	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	7,248	7,924
Purchased credit impaired loans	3,524	2,107
Residential Real Estate | Substandard | Residential Line of Credit
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	1,039	2,304
Residential Real Estate | Substandard | Multi-Family Mortgage
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	1,626	1,027
Purchased credit impaired loans	22	28
Commercial Real Estate | Owner Occupied
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	462,322	353,564
Purchased credit impaired loans	11,073	3,782
Gross loans	473,395	357,346
Commercial Real Estate | Non-Owner Occupied
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	502,445	262,562
Purchased credit impaired loans	18,971	5,340
Gross loans	521,416	267,902
Commercial Real Estate | Pass | Owner Occupied
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	429,691	338,698
Commercial Real Estate | Pass | Non-Owner Occupied
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	486,487	249,877
Commercial Real Estate | Watch | Owner Occupied
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	27,960	10,459
Purchased credit impaired loans	3,294
Commercial Real Estate | Watch | Non-Owner Occupied
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	13,967	10,273
Purchased credit impaired loans	7,740
Commercial Real Estate | Substandard | Owner Occupied
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	4,671	4,407
Purchased credit impaired loans	7,779	3,782
Commercial Real Estate | Substandard | Non-Owner Occupied
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	1,991	2,412
Purchased credit impaired loans	11,231	5,340
Consumer and Other
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	204,105	74,303
Purchased credit impaired loans	26,781	4
Gross loans	230,886	74,307
Consumer and Other | Pass
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	202,697	73,454
Consumer and Other | Watch
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	930	417
Purchased credit impaired loans	18,181
Consumer and Other | Substandard
Financing Receivable Allowance For Credit Losses [Line Items]
Loans, excluding purchased credit impaired loans	478	432
Purchased credit impaired loans	$ 8,600	$ 4