Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Financial assets:
Securities available for sale	$ 948,365	$ 671,488
Recurring
Financial assets:
Securities available for sale	948,365	671,488
Derivative instruments	9,311	5,977
Mortgage loans held for sale	204,472	108,316
Total financial assets	1,162,148	785,781
Financial liabilities:
Derivative instruments	5,950	6,039
Total financial liabilities	5,950	6,039
Recurring | Interest rate swaps
Financial liabilities:
Derivative instruments	1,385	2,536
Recurring | Interest rate contracts
Financial assets:
Derivative instruments	3,636	3,171
Financial liabilities:
Derivative instruments	3,636	3,171
Recurring | Interest rate lock commitments
Financial assets:
Derivative instruments	4,940	2,756
Financial liabilities:
Derivative instruments	4	4
Recurring | Forward commitments
Financial assets:
Derivative instruments	735	50
Financial liabilities:
Derivative instruments	925	328
Recurring | Trust preferred securities
Financial assets:
Securities available for sale	10,045	9,388
Recurring | Other debt securities
Financial assets:
Securities available for sale	23,940	17,290
Recurring | Obligations of other U.S. Government agencies and corporations
Financial assets:
Securities available for sale	3,528	3,564
Recurring | Obligations of states and political subdivisions
Financial assets:
Securities available for sale	226,342	234,481
Recurring | Government agency mortgage backed securities | Residential mortgage-backed securities
Financial assets:
Securities available for sale	409,470	193,950
Recurring | Government agency mortgage backed securities | Commercial mortgage-backed securities
Financial assets:
Securities available for sale	27,502	31,170
Recurring | Government agency collateralized mortgage obligations | Residential mortgage-backed securities
Financial assets:
Securities available for sale	237,666	176,639
Recurring | Government agency collateralized mortgage obligations | Commercial mortgage-backed securities
Financial assets:
Securities available for sale	9,872	5,006
Recurring | Level 1
Financial assets:
Securities available for sale	0	0
Derivative instruments	0	0
Mortgage loans held for sale	0	0
Total financial assets	0	0
Financial liabilities:
Derivative instruments	0	0
Total financial liabilities	0	0
Recurring | Level 1 | Interest rate swaps
Financial liabilities:
Derivative instruments	0	0
Recurring | Level 1 | Interest rate contracts
Financial assets:
Derivative instruments	0	0
Financial liabilities:
Derivative instruments	0	0
Recurring | Level 1 | Interest rate lock commitments
Financial assets:
Derivative instruments	0	0
Financial liabilities:
Derivative instruments	0	0
Recurring | Level 1 | Forward commitments
Financial assets:
Derivative instruments	0	0
Financial liabilities:
Derivative instruments	0	0
Recurring | Level 1 | Trust preferred securities
Financial assets:
Securities available for sale	0	0
Recurring | Level 1 | Other debt securities
Financial assets:
Securities available for sale	0	0
Recurring | Level 1 | Obligations of other U.S. Government agencies and corporations
Financial assets:
Securities available for sale	0	0
Recurring | Level 1 | Obligations of states and political subdivisions
Financial assets:
Securities available for sale	0	0
Recurring | Level 1 | Government agency mortgage backed securities | Residential mortgage-backed securities
Financial assets:
Securities available for sale	0	0
Recurring | Level 1 | Government agency mortgage backed securities | Commercial mortgage-backed securities
Financial assets:
Securities available for sale	0	0
Recurring | Level 1 | Government agency collateralized mortgage obligations | Residential mortgage-backed securities
Financial assets:
Securities available for sale	0	0
Recurring | Level 1 | Government agency collateralized mortgage obligations | Commercial mortgage-backed securities
Financial assets:
Securities available for sale	0	0
Recurring | Level 2
Financial assets:
Securities available for sale	938,320	662,100
Derivative instruments	9,311	5,977
Mortgage loans held for sale	204,472	108,316
Total financial assets	1,152,103	776,393
Financial liabilities:
Derivative instruments	5,950	6,039
Total financial liabilities	5,950	6,039
Recurring | Level 2 | Interest rate swaps
Financial liabilities:
Derivative instruments	1,385	2,536
Recurring | Level 2 | Interest rate contracts
Financial assets:
Derivative instruments	3,636	3,171
Financial liabilities:
Derivative instruments	3,636	3,171
Recurring | Level 2 | Interest rate lock commitments
Financial assets:
Derivative instruments	4,940	2,756
Financial liabilities:
Derivative instruments	4	4
Recurring | Level 2 | Forward commitments
Financial assets:
Derivative instruments	735	50
Financial liabilities:
Derivative instruments	925	328
Recurring | Level 2 | Trust preferred securities
Financial assets:
Securities available for sale	0	0
Recurring | Level 2 | Other debt securities
Financial assets:
Securities available for sale	23,940	17,290
Recurring | Level 2 | Obligations of other U.S. Government agencies and corporations
Financial assets:
Securities available for sale	3,528	3,564
Recurring | Level 2 | Obligations of states and political subdivisions
Financial assets:
Securities available for sale	226,342	234,481
Recurring | Level 2 | Government agency mortgage backed securities | Residential mortgage-backed securities
Financial assets:
Securities available for sale	409,470	193,950
Recurring | Level 2 | Government agency mortgage backed securities | Commercial mortgage-backed securities
Financial assets:
Securities available for sale	27,502	31,170
Recurring | Level 2 | Government agency collateralized mortgage obligations | Residential mortgage-backed securities
Financial assets:
Securities available for sale	237,666	176,639
Recurring | Level 2 | Government agency collateralized mortgage obligations | Commercial mortgage-backed securities
Financial assets:
Securities available for sale	9,872	5,006
Recurring | Level 3
Financial assets:
Securities available for sale	10,045	9,388
Derivative instruments	0	0
Mortgage loans held for sale	0	0
Total financial assets	10,045	9,388
Financial liabilities:
Derivative instruments	0	0
Total financial liabilities	0	0
Recurring | Level 3 | Interest rate swaps
Financial liabilities:
Derivative instruments	0	0
Recurring | Level 3 | Interest rate contracts
Financial assets:
Derivative instruments	0	0
Financial liabilities:
Derivative instruments	0	0
Recurring | Level 3 | Interest rate lock commitments
Financial assets:
Derivative instruments	0	0
Financial liabilities:
Derivative instruments	0	0
Recurring | Level 3 | Forward commitments
Financial assets:
Derivative instruments	0	0
Financial liabilities:
Derivative instruments	0	0
Recurring | Level 3 | Trust preferred securities
Financial assets:
Securities available for sale	10,045	9,388
Recurring | Level 3 | Other debt securities
Financial assets:
Securities available for sale	0	0
Recurring | Level 3 | Obligations of other U.S. Government agencies and corporations
Financial assets:
Securities available for sale	0	0
Recurring | Level 3 | Obligations of states and political subdivisions
Financial assets:
Securities available for sale	0	0
Recurring | Level 3 | Government agency mortgage backed securities | Residential mortgage-backed securities
Financial assets:
Securities available for sale	0	0
Recurring | Level 3 | Government agency mortgage backed securities | Commercial mortgage-backed securities
Financial assets:
Securities available for sale	0	0
Recurring | Level 3 | Government agency collateralized mortgage obligations | Residential mortgage-backed securities
Financial assets:
Securities available for sale	0	0
Recurring | Level 3 | Government agency collateralized mortgage obligations | Commercial mortgage-backed securities
Financial assets:
Securities available for sale	$ 0	$ 0