Securities - Exposure to Bond Issuers that Exceeded 10% of Stockholders' Equity (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Exposure to investment securities issuers that exceeded 10% of shareholders' equity [Abstract]
Amortized Cost	$ 269,267	$ 405,303
Stockholders' Equity, Total
Exposure to investment securities issuers that exceeded 10% of shareholders' equity [Abstract]
Amortized Cost	175,194
Fair Value	175,092
Stockholders' Equity, Total | U.S. Government Treasuries (U.S.)
Exposure to investment securities issuers that exceeded 10% of shareholders' equity [Abstract]
Amortized Cost	18,594
Fair Value	18,592
Stockholders' Equity, Total | Federal Home Loan Bank (FHLB)
Exposure to investment securities issuers that exceeded 10% of shareholders' equity [Abstract]
Amortized Cost	18,746
Fair Value	18,741
Stockholders' Equity, Total | Federal Home Loan Mortgage Corporation (Freddie Mac-FHLMC)
Exposure to investment securities issuers that exceeded 10% of shareholders' equity [Abstract]
Amortized Cost	44,982
Fair Value	44,974
Stockholders' Equity, Total | Federal National Mortgage Association (Fannie Mae-FNMA)
Exposure to investment securities issuers that exceeded 10% of shareholders' equity [Abstract]
Amortized Cost	71,145
Fair Value	71,097
Stockholders' Equity, Total | Federal Farm Credit Bank (FFCB)
Exposure to investment securities issuers that exceeded 10% of shareholders' equity [Abstract]
Amortized Cost	21,727
Fair Value	$ 21,688