Loans - Summary of Recorded Investment by Risk Category of Portfolio Loans by Portfolio Class and Category (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross	$ 4,267,430	$ 4,097,050
Non-Covered Loans
Financing Receivable, Recorded Investment [Line Items]
Loans, before unearned loan fees	4,219,689	4,024,221
Loans and Leases Receivable, Gross	4,218,341	4,022,896
Non-Covered Loans | Commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Loans, before unearned loan fees	2,032,929	1,918,720
Non-Covered Loans | CRE - investor owned
Financing Receivable, Recorded Investment [Line Items]
Loans, before unearned loan fees	826,447	769,275
Non-Covered Loans | CRE - owner occupied
Financing Receivable, Recorded Investment [Line Items]
Loans, before unearned loan fees	589,045	554,589
Non-Covered Loans | Construction and land development
Financing Receivable, Recorded Investment [Line Items]
Loans, before unearned loan fees	326,858	303,091
Non-Covered Loans | Residential real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, before unearned loan fees	308,385	341,312
Non-Covered Loans | Consumer and other
Financing Receivable, Recorded Investment [Line Items]
Loans, before unearned loan fees	136,025	137,234
Loans and Leases Receivable, Gross	134,677	135,909
Pass (1-6) | Non-Covered Loans
Financing Receivable, Recorded Investment [Line Items]
Loans, before unearned loan fees	3,921,764	3,794,940
Pass (1-6) | Non-Covered Loans | Commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Loans, before unearned loan fees	1,835,230	1,769,102
Pass (1-6) | Non-Covered Loans | CRE - investor owned
Financing Receivable, Recorded Investment [Line Items]
Loans, before unearned loan fees	798,116	754,010
Pass (1-6) | Non-Covered Loans | CRE - owner occupied
Financing Receivable, Recorded Investment [Line Items]
Loans, before unearned loan fees	540,961	514,616
Pass (1-6) | Non-Covered Loans | Construction and land development
Financing Receivable, Recorded Investment [Line Items]
Loans, before unearned loan fees	315,022	292,766
Pass (1-6) | Non-Covered Loans | Residential real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, before unearned loan fees	298,076	329,742
Pass (1-6) | Non-Covered Loans | Consumer and other
Financing Receivable, Recorded Investment [Line Items]
Loans, before unearned loan fees	134,359	134,704
Watch (7) | Non-Covered Loans
Financing Receivable, Recorded Investment [Line Items]
Loans, before unearned loan fees	223,282	152,923
Watch (7) | Non-Covered Loans | Commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Loans, before unearned loan fees	142,768	94,002
Watch (7) | Non-Covered Loans | CRE - investor owned
Financing Receivable, Recorded Investment [Line Items]
Loans, before unearned loan fees	22,275	10,840
Watch (7) | Non-Covered Loans | CRE - owner occupied
Financing Receivable, Recorded Investment [Line Items]
Loans, before unearned loan fees	43,399	34,440
Watch (7) | Non-Covered Loans | Construction and land development
Financing Receivable, Recorded Investment [Line Items]
Loans, before unearned loan fees	11,775	9,983
Watch (7) | Non-Covered Loans | Residential real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, before unearned loan fees	3,058	3,648
Watch (7) | Non-Covered Loans | Consumer and other
Financing Receivable, Recorded Investment [Line Items]
Loans, before unearned loan fees	7	10
Classified (8 & 9) | Non-Covered Loans
Financing Receivable, Recorded Investment [Line Items]
Loans, before unearned loan fees	73,295	75,033
Classified (8 & 9) | Non-Covered Loans | Commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
Loans, before unearned loan fees	54,931	55,616
Classified (8 & 9) | Non-Covered Loans | CRE - investor owned
Financing Receivable, Recorded Investment [Line Items]
Loans, before unearned loan fees	6,056	4,425
Classified (8 & 9) | Non-Covered Loans | CRE - owner occupied
Financing Receivable, Recorded Investment [Line Items]
Loans, before unearned loan fees	4,685	5,533
Classified (8 & 9) | Non-Covered Loans | Construction and land development
Financing Receivable, Recorded Investment [Line Items]
Loans, before unearned loan fees	61	342
Classified (8 & 9) | Non-Covered Loans | Residential real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, before unearned loan fees	7,251	7,922
Classified (8 & 9) | Non-Covered Loans | Consumer and other
Financing Receivable, Recorded Investment [Line Items]
Loans, before unearned loan fees	$ 311	$ 1,195