Securities - Contractual Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Amortized Cost
Due within one year	$ 17,132
Due after one year through five years	30,969
Due after five years through ten years	78,892
Due after ten years	120,038
Amortized Cost	1,276,871	$ 1,264,529
Fair Value
Due within one year	17,294
Due after one year through five years	31,820
Due after five years through ten years	81,860
Due after ten years	118,890
Fair Value	1,290,613	1,250,777
Residential mortgage backed securities | Government agency mortgage backed securities
Amortized Cost
Without single maturity date, amortized cost	708,970
Amortized Cost	708,970	621,690
Fair Value
Without single maturity date, fair value	716,105
Fair Value	716,105	613,283
Residential mortgage backed securities | Government agency collateralized mortgage obligations
Amortized Cost
Without single maturity date, amortized cost	172,178
Amortized Cost	172,178	332,697
Fair Value
Without single maturity date, fair value	173,238
Fair Value	173,238	326,989
Commercial mortgage backed securities | Government agency mortgage backed securities
Amortized Cost
Without single maturity date, amortized cost	30,372
Amortized Cost	30,372	21,957
Fair Value
Without single maturity date, fair value	31,007
Fair Value	31,007	21,830
Commercial mortgage backed securities | Government agency collateralized mortgage obligations
Amortized Cost
Without single maturity date, amortized cost	76,456
Amortized Cost	76,456	28,446
Fair Value
Without single maturity date, fair value	77,751
Fair Value	77,751	28,335
Other debt securities
Amortized Cost
Without single maturity date, amortized cost	41,864
Amortized Cost	55,364	44,046
Fair Value
Without single maturity date, fair value	42,648
Fair Value	$ 56,365	$ 43,927