Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Financial assets:
Securities available for sale	$ 1,088,779	$ 671,488
Derivative instruments	181	0
Recurring
Financial assets:
Securities available for sale	1,088,779	671,488
Derivative instruments	9,120	5,977
Mortgage loans held for sale	245,046	108,316
Total financial assets	1,342,945	785,781
Financial liabilities:
Derivative instruments	6,491	6,039
Total financial liabilities	6,491	6,039
Recurring | Interest rate swaps
Financial assets:
Derivative instruments	181
Financial liabilities:
Derivative instruments	1,047	2,536
Recurring | Interest rate contracts
Financial assets:
Derivative instruments	4,142	3,171
Financial liabilities:
Derivative instruments	4,142	3,171
Recurring | Interest rate lock commitments
Financial assets:
Derivative instruments	4,699	2,756
Financial liabilities:
Derivative instruments	1	4
Recurring | Forward commitments
Financial assets:
Derivative instruments	98	50
Financial liabilities:
Derivative instruments	1,301	328
Recurring | Trust preferred securities
Financial assets:
Securities available for sale	10,401	9,388
Recurring | Other debt securities
Financial assets:
Securities available for sale	23,347	17,290
Recurring | Obligations of other U.S. Government agencies and corporations
Financial assets:
Securities available for sale	3,515	3,564
Recurring | Obligations of states and political subdivisions
Financial assets:
Securities available for sale	220,876	234,481
Recurring | Government agency mortgage backed securities | Residential mortgage backed securities:
Financial assets:
Securities available for sale	483,125	193,950
Recurring | Government agency mortgage backed securities | Commercial mortgage-backed securities
Financial assets:
Securities available for sale	27,189	31,170
Recurring | Government agency collateralized mortgage obligations | Residential mortgage backed securities:
Financial assets:
Securities available for sale	296,005	176,639
Recurring | Government agency collateralized mortgage obligations | Commercial mortgage-backed securities
Financial assets:
Securities available for sale	24,321	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 assets:
Derivative instruments	0
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	1,078,378	662,100
Derivative instruments	9,120	5,977
Mortgage loans held for sale	245,046	108,316
Total financial assets	1,332,544	776,393
Financial liabilities:
Derivative instruments	6,491	6,039
Total financial liabilities	6,491	6,039
Recurring | Level 2 | Interest rate swaps
Financial liabilities:
Derivative instruments	1,047	2,536
Recurring | Level 2 | Interest rate contracts
Financial assets:
Derivative instruments	4,142	3,171
Financial liabilities:
Derivative instruments	4,142	3,171
Recurring | Level 2 | Interest rate lock commitments
Financial assets:
Derivative instruments	4,699	2,756
Financial liabilities:
Derivative instruments	1	4
Recurring | Level 2 | Forward commitments
Financial assets:
Derivative instruments	98	50
Financial liabilities:
Derivative instruments	1,301	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	23,347	17,290
Recurring | Level 2 | Obligations of other U.S. Government agencies and corporations
Financial assets:
Securities available for sale	3,515	3,564
Recurring | Level 2 | Obligations of states and political subdivisions
Financial assets:
Securities available for sale	220,876	234,481
Recurring | Level 2 | Government agency mortgage backed securities | Residential mortgage backed securities:
Financial assets:
Securities available for sale	483,125	193,950
Recurring | Level 2 | Government agency mortgage backed securities | Commercial mortgage-backed securities
Financial assets:
Securities available for sale	27,189	31,170
Recurring | Level 2 | Government agency collateralized mortgage obligations | Residential mortgage backed securities:
Financial assets:
Securities available for sale	296,005	176,639
Recurring | Level 2 | Government agency collateralized mortgage obligations | Commercial mortgage-backed securities
Financial assets:
Securities available for sale	24,321	5,006
Recurring | Level 3
Financial assets:
Securities available for sale	10,401	9,388
Derivative instruments	0	0
Mortgage loans held for sale	0	0
Total financial assets	10,401	9,388
Financial liabilities:
Derivative instruments	0	0
Total financial liabilities	0	0
Recurring | Level 3 | Interest rate swaps
Financial assets:
Derivative instruments	0
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	10,401	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