Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financial assets:
Securities available for sale	$ 1,150,459	$ 674,248
Trust preferred securities
Financial assets:
Securities available for sale	8,960	18,389
Other debt securities
Financial assets:
Securities available for sale	26,919	22,145
Obligations of other U.S. Government agencies and corporations
Financial assets:
Securities available for sale	14,638	2,158
Obligations of states and political subdivisions
Financial assets:
Securities available for sale	350,354
Government agency mortgage backed securities | Residential mortgage-backed securities
Financial assets:
Securities available for sale	459,558	409,317
Government agency mortgage backed securities | Commercial mortgage-backed securities
Financial assets:
Securities available for sale	45,929	50,863
Government agency collateralized mortgage obligations | Residential mortgage-backed securities
Financial assets:
Securities available for sale	232,658	168,826
Government agency collateralized mortgage obligations | Commercial mortgage-backed securities
Financial assets:
Securities available for sale	11,443	2,550
Recurring
Financial assets:
Securities available for sale	1,150,459	674,248
Derivative instruments	8,569	9,108
Mortgage loans held for sale	207,288	177,866
Total financial assets	1,366,316	861,222
Financial liabilities:
Derivative instruments	8,429	5,910
Total financial liabilities	8,429	5,910
Recurring | Interest rate swaps
Financial liabilities:
Derivative instruments	3,242	3,410
Recurring | Interest rate contracts
Financial assets:
Derivative instruments	4,681	1,985
Financial liabilities:
Derivative instruments	4,681	1,985
Recurring | Interest rate lock commitments
Financial assets:
Derivative instruments	3,327	2,643
Financial liabilities:
Derivative instruments	57	246
Recurring | Forward commitments
Financial assets:
Derivative instruments	561	4,480
Financial liabilities:
Derivative instruments	449	269
Recurring | Trust preferred securities
Financial assets:
Securities available for sale	8,960	18,389
Recurring | Other debt securities
Financial assets:
Securities available for sale	26,919	22,145
Recurring | Obligations of other U.S. Government agencies and corporations
Financial assets:
Securities available for sale	14,638	2,158
Recurring | Obligations of states and political subdivisions
Financial assets:
Securities available for sale	350,354
Recurring | Government agency mortgage backed securities | Residential mortgage-backed securities
Financial assets:
Securities available for sale	459,558	409,317
Recurring | Government agency mortgage backed securities | Commercial mortgage-backed securities
Financial assets:
Securities available for sale	45,929	50,863
Recurring | Government agency collateralized mortgage obligations | Residential mortgage-backed securities
Financial assets:
Securities available for sale	232,658	168,826
Recurring | Government agency collateralized mortgage obligations | Commercial mortgage-backed securities
Financial assets:
Securities available for sale	11,443	2,550
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
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	1,141,499	655,859
Derivative instruments	8,569	9,108
Mortgage loans held for sale	207,288	177,866
Total financial assets	1,357,356	842,833
Financial liabilities:
Derivative instruments	8,429	5,910
Total financial liabilities	8,429	5,910
Recurring | Level 2 | Interest rate swaps
Financial liabilities:
Derivative instruments	3,242	3,410
Recurring | Level 2 | Interest rate contracts
Financial assets:
Derivative instruments	4,681	1,985
Financial liabilities:
Derivative instruments	4,681	1,985
Recurring | Level 2 | Interest rate lock commitments
Financial assets:
Derivative instruments	3,327	2,643
Financial liabilities:
Derivative instruments	57	246
Recurring | Level 2 | Forward commitments
Financial assets:
Derivative instruments	561	4,480
Financial liabilities:
Derivative instruments	449	269
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	26,919	22,145
Recurring | Level 2 | Obligations of other U.S. Government agencies and corporations
Financial assets:
Securities available for sale	14,638	2,158
Recurring | Level 2 | Obligations of states and political subdivisions
Financial assets:
Securities available for sale	350,354
Recurring | Level 2 | Government agency mortgage backed securities | Residential mortgage-backed securities
Financial assets:
Securities available for sale	459,558	409,317
Recurring | Level 2 | Government agency mortgage backed securities | Commercial mortgage-backed securities
Financial assets:
Securities available for sale	45,929	50,863
Recurring | Level 2 | Government agency collateralized mortgage obligations | Residential mortgage-backed securities
Financial assets:
Securities available for sale	232,658	168,826
Recurring | Level 2 | Government agency collateralized mortgage obligations | Commercial mortgage-backed securities
Financial assets:
Securities available for sale	11,443	2,550
Recurring | Level 3
Financial assets:
Securities available for sale	8,960	18,389
Derivative instruments	0	0
Mortgage loans held for sale	0	0
Total financial assets	8,960	18,389
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	8,960	18,389
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
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