Portfolio Loans - Summary of Aging of Recorded Investment in Past Due Portfolio Loans by Portfolio Class and Category (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, including unearned loan fees	$ 4,097,050	$ 3,158,161
Non-Covered Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	10,828	999
Financing Receivable, Recorded Investment, 90 Days Past Due	2,715	2,099
Total Past Due	13,543	3,098
Current	4,009,353	3,115,294
Total	4,024,221	3,119,154
Loans, including unearned loan fees	4,022,896	3,118,392
Non-Covered Loans | Commercial and industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	7,882	334
Financing Receivable, Recorded Investment, 90 Days Past Due	1,770	171
Total Past Due	9,652	505
Current	1,909,068	1,632,209
Total	1,918,720	1,632,714
Non-Covered Loans | CRE - investor owned
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	934	0
Financing Receivable, Recorded Investment, 90 Days Past Due	0	175
Total Past Due	934	175
Current	768,341	544,633
Total	769,275	544,808
Non-Covered Loans | CRE - owner occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	0	212
Financing Receivable, Recorded Investment, 90 Days Past Due	0	225
Total Past Due	0	437
Current	554,589	349,711
Total	554,589	350,148
Non-Covered Loans | Construction and land development
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	76	355
Financing Receivable, Recorded Investment, 90 Days Past Due	0	1,528
Total Past Due	76	1,883
Current	303,015	192,659
Total	303,091	194,542
Non-Covered Loans | Residential real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	1,529	91
Financing Receivable, Recorded Investment, 90 Days Past Due	945	0
Total Past Due	2,474	91
Current	338,838	240,669
Total	341,312	240,760
Non-Covered Loans | Consumer and other
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	407	7
Financing Receivable, Recorded Investment, 90 Days Past Due	0	0
Total Past Due	407	7
Current	135,502	155,413
Total	137,234	156,182
Loans, including unearned loan fees	$ 135,909	$ 155,420