Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Investment securities:
Held-to-Maturity, Estimated Fair Value	$ 553,323	$ 584,533
Stockholders' equity:
Nonvoting noncumulative preferred stock, par value	$ 0	$ 0
Nonvoting noncumulative preferred stock, authorized shares	100,000	100,000
Nonvoting noncumulative preferred stock, issued shares	0	0
Nonvoting noncumulative preferred stock, outstanding shares	0	0

Fair value of investments in debt securities classified as held-to-maturity.

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