Securities, Exposure to Investment Securities Issuers That Exceeded 10 Percent of Stockholders' Equity (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Exposure to investment securities issuers that exceeded 10% of shareholders' equity [Abstract]
Amortized cost	$ 546,121	$ 641,603
Stockholders' Equity, Total [Member]
Exposure to investment securities issuers that exceeded 10% of shareholders' equity [Abstract]
Amortized cost	394,007
Fair value	390,567
Stockholders' Equity, Total [Member] | U.S. Treasuries [Member]
Exposure to investment securities issuers that exceeded 10% of shareholders' equity [Abstract]
Amortized cost	29,999
Fair value	29,999
Stockholders' Equity, Total [Member] | Federal Home Loan Bank (FHLB) [Member]
Exposure to investment securities issuers that exceeded 10% of shareholders' equity [Abstract]
Amortized cost	85,507
Fair value	84,689
Stockholders' Equity, Total [Member] | Federal Home Loan Mortgage Corporation (Freddie Mac-FHLMC) [Member]
Exposure to investment securities issuers that exceeded 10% of shareholders' equity [Abstract]
Amortized cost	66,271
Fair value	65,589
Stockholders' Equity, Total [Member] | Federal National Mortgage Association (Fannie Mae-FNMA) [Member]
Exposure to investment securities issuers that exceeded 10% of shareholders' equity [Abstract]
Amortized cost	127,504
Fair value	126,294
Stockholders' Equity, Total [Member] | Federal Farm Credit Bank (FFCB) [Member]
Exposure to investment securities issuers that exceeded 10% of shareholders' equity [Abstract]
Amortized cost	84,726
Fair value	$ 83,996