Debt Securities Held to Maturity Expected Maturities of Held-to-Maturity Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Amortized cost
Amortized cost	$ 287,529	$ 262,143
Fair value
Fair value	284,450	254,841
U.S. government and agency obligations
Amortized cost
More than one year to five years	5,000
More than five years to ten years	18,406
More than ten years	10,000
Amortized cost	33,406	23,404
Fair value
More than one year to five years	5,003
More than five years to ten years	18,361
More than ten years	10,063
Fair value	33,427	23,241
Mortgage-backed securities and collateralized mortgage obligations
Amortized cost
Amortized cost	254,123	238,739
Fair value
Fair value	$ 251,023	$ 231,600

Amount of investment in debt security measured at amortized cost (held-to-maturity).

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