Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Financial assets:
Securities available for sale, at fair value	$ 1,238,577	$ 1,250,777
Mortgage loans held for sale in loans held for sale	392,448	219,848
Trust preferred securities
Financial assets:
Securities available for sale, at fair value	9,862	10,633
Other debt securities
Financial assets:
Securities available for sale, at fair value	48,249	43,927
Government agency mortgage backed securities | Residential mortgage backed securities
Financial assets:
Securities available for sale, at fair value	666,167	613,283
Government agency mortgage backed securities | Commercial mortgage-backed securities
Financial assets:
Securities available for sale, at fair value	27,666	21,830
Government agency collateralized mortgage obligations | Residential mortgage backed securities
Financial assets:
Securities available for sale, at fair value	191,187	326,989
Government agency collateralized mortgage obligations | Commercial mortgage-backed securities
Financial assets:
Securities available for sale, at fair value	75,423	28,335
Recurring
Financial assets:
Securities available for sale, at fair value	1,238,577	1,250,777
Derivative instruments	12,329	6,519
Mortgage loans held for sale in loans held for sale	392,448	219,848
Total financial assets	1,643,354	1,477,144
Financial liabilities:
Derivative instruments	12,495	8,388
Total financial liabilities	12,495	8,388
Recurring | Interest rate contracts
Financial assets:
Derivative instruments	5,055	2,779
Financial liabilities:
Derivative instruments	5,055	2,779
Recurring | Interest rate swaps
Financial liabilities:
Derivative instruments	6,290	2,046
Recurring | Interest rate lock commitments
Financial assets:
Derivative instruments	6,694	3,740
Financial liabilities:
Derivative instruments	14
Recurring | Forward commitments
Financial assets:
Derivative instruments	580
Financial liabilities:
Derivative instruments	1,136	3,563
Recurring | Trust preferred securities
Financial assets:
Securities available for sale, at fair value	9,862	10,633
Recurring | Other debt securities
Financial assets:
Securities available for sale, at fair value	48,249	43,927
Recurring | U.S. Treasury securities
Financial assets:
Securities available for sale, at fair value	498
Recurring | Obligations of other U.S. Government agencies and corporations
Financial assets:
Securities available for sale, at fair value	2,537	2,511
Recurring | Obligations of states and political subdivisions
Financial assets:
Securities available for sale, at fair value	216,988	203,269
Recurring | Government agency mortgage backed securities | Residential mortgage backed securities
Financial assets:
Securities available for sale, at fair value	666,167	613,283
Recurring | Government agency mortgage backed securities | Commercial mortgage-backed securities
Financial assets:
Securities available for sale, at fair value	27,666	21,830
Recurring | Government agency collateralized mortgage obligations | Residential mortgage backed securities
Financial assets:
Securities available for sale, at fair value	191,187	326,989
Recurring | Government agency collateralized mortgage obligations | Commercial mortgage-backed securities
Financial assets:
Securities available for sale, at fair value	75,423	28,335
Recurring | Level 1
Financial assets:
Securities available for sale, at fair value	0	0
Derivative instruments	0	0
Mortgage loans held for sale in 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 contracts
Financial assets:
Derivative instruments	0	0
Financial liabilities:
Derivative instruments	0	0
Recurring | Level 1 | Interest rate swaps
Financial liabilities:
Derivative instruments	0	0
Recurring | Level 1 | Interest rate lock commitments
Financial assets:
Derivative instruments	0	0
Financial liabilities:
Derivative instruments	0
Recurring | Level 1 | Forward commitments
Financial assets:
Derivative instruments	0
Financial liabilities:
Derivative instruments	0	0
Recurring | Level 1 | Trust preferred securities
Financial assets:
Securities available for sale, at fair value	0	0
Recurring | Level 1 | Other debt securities
Financial assets:
Securities available for sale, at fair value	0	0
Recurring | Level 1 | U.S. Treasury securities
Financial assets:
Securities available for sale, at fair value	0
Recurring | Level 1 | Obligations of other U.S. Government agencies and corporations
Financial assets:
Securities available for sale, at fair value	0	0
Recurring | Level 1 | Obligations of states and political subdivisions
Financial assets:
Securities available for sale, at fair value	0	0
Recurring | Level 1 | Government agency mortgage backed securities | Residential mortgage backed securities
Financial assets:
Securities available for sale, at fair value	0	0
Recurring | Level 1 | Government agency mortgage backed securities | Commercial mortgage-backed securities
Financial assets:
Securities available for sale, at fair value	0	0
Recurring | Level 1 | Government agency collateralized mortgage obligations | Residential mortgage backed securities
Financial assets:
Securities available for sale, at fair value	0	0
Recurring | Level 1 | Government agency collateralized mortgage obligations | Commercial mortgage-backed securities
Financial assets:
Securities available for sale, at fair value	0	0
Recurring | Level 2
Financial assets:
Securities available for sale, at fair value	1,228,715	1,240,144
Derivative instruments	12,329	6,519
Mortgage loans held for sale in loans held for sale	392,448	219,848
Total financial assets	1,633,492	1,466,511
Financial liabilities:
Derivative instruments	12,495	8,388
Total financial liabilities	12,495	8,388
Recurring | Level 2 | Interest rate contracts
Financial assets:
Derivative instruments	5,055	2,779
Financial liabilities:
Derivative instruments	5,055	2,779
Recurring | Level 2 | Interest rate swaps
Financial liabilities:
Derivative instruments	6,290	2,046
Recurring | Level 2 | Interest rate lock commitments
Financial assets:
Derivative instruments	6,694	3,740
Financial liabilities:
Derivative instruments	14
Recurring | Level 2 | Forward commitments
Financial assets:
Derivative instruments	580
Financial liabilities:
Derivative instruments	1,136	3,563
Recurring | Level 2 | Trust preferred securities
Financial assets:
Securities available for sale, at fair value	0	0
Recurring | Level 2 | Other debt securities
Financial assets:
Securities available for sale, at fair value	48,249	43,927
Recurring | Level 2 | U.S. Treasury securities
Financial assets:
Securities available for sale, at fair value	498
Recurring | Level 2 | Obligations of other U.S. Government agencies and corporations
Financial assets:
Securities available for sale, at fair value	2,537	2,511
Recurring | Level 2 | Obligations of states and political subdivisions
Financial assets:
Securities available for sale, at fair value	216,988	203,269
Recurring | Level 2 | Government agency mortgage backed securities | Residential mortgage backed securities
Financial assets:
Securities available for sale, at fair value	666,167	613,283
Recurring | Level 2 | Government agency mortgage backed securities | Commercial mortgage-backed securities
Financial assets:
Securities available for sale, at fair value	27,666	21,830
Recurring | Level 2 | Government agency collateralized mortgage obligations | Residential mortgage backed securities
Financial assets:
Securities available for sale, at fair value	191,187	326,989
Recurring | Level 2 | Government agency collateralized mortgage obligations | Commercial mortgage-backed securities
Financial assets:
Securities available for sale, at fair value	75,423	28,335
Recurring | Level 3
Financial assets:
Securities available for sale, at fair value	9,862	10,633
Derivative instruments	0	0
Mortgage loans held for sale in loans held for sale	0	0
Total financial assets	9,862	10,633
Financial liabilities:
Derivative instruments	0	0
Total financial liabilities	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 swaps
Financial liabilities:
Derivative instruments	0	0
Recurring | Level 3 | Interest rate lock commitments
Financial assets:
Derivative instruments	0	0
Financial liabilities:
Derivative instruments	0
Recurring | Level 3 | Forward commitments
Financial assets:
Derivative instruments	0
Financial liabilities:
Derivative instruments	0	0
Recurring | Level 3 | Trust preferred securities
Financial assets:
Securities available for sale, at fair value	9,862	10,633
Recurring | Level 3 | Other debt securities
Financial assets:
Securities available for sale, at fair value	0	0
Recurring | Level 3 | U.S. Treasury securities
Financial assets:
Securities available for sale, at fair value	0
Recurring | Level 3 | Obligations of other U.S. Government agencies and corporations
Financial assets:
Securities available for sale, at fair value	0	0
Recurring | Level 3 | Obligations of states and political subdivisions
Financial assets:
Securities available for sale, at fair value	0	0
Recurring | Level 3 | Government agency mortgage backed securities | Residential mortgage backed securities
Financial assets:
Securities available for sale, at fair value	0	0
Recurring | Level 3 | Government agency mortgage backed securities | Commercial mortgage-backed securities
Financial assets:
Securities available for sale, at fair value	0	0
Recurring | Level 3 | Government agency collateralized mortgage obligations | Residential mortgage backed securities
Financial assets:
Securities available for sale, at fair value	0	0
Recurring | Level 3 | Government agency collateralized mortgage obligations | Commercial mortgage-backed securities
Financial assets:
Securities available for sale, at fair value	$ 0	$ 0