Investment Securities Schedule of Held-to-Maturity Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule of Held-to-maturity Securities [Line Items]
Due within 1 year	$ 0
Held-to-maturity Securities, Debt Maturities, Next Twelve Months, Fair Value	0
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	770	$ 60
Held-to-maturity Securities	436,081	372,513
Securities held to maturity, fair value	434,882	$ 368,618
Due after 1 but within 5 years	3,104
Due after 5 but within 10 years	34,126
Held-to-maturity Securities, Debt Maturities, Year Six Through Ten, Fair Value	34,354
Held-to-maturity Securities, Debt Maturities, Year Two Through Five, Fair Value	3,131
Due after 10 years	3,542
Held-to-maturity Securities, Debt Maturities, after Ten Years, Fair Value	3,556
Held-to-maturity Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis	40,772
Held-to-maturity Securities, Debt Maturities, Single Maturity Date, Fair Value	41,041
Held-to-maturity Securities, Debt Maturities, without Single Maturity Date, Net Carrying Amount	395,309
Held-to-maturity Securities, Debt Maturities, without Single Maturity Date, Fair Value	393,841
US Government Agencies Residential Mortgage-backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity Securities	62,600
Securities held to maturity, fair value	61,800
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity Securities	332,700
Securities held to maturity, fair value	$ 332,100