Consolidated Balance Sheets (Unaudited) (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Investment securities:
Held-to-Maturity, Estimated Fair Value	$ 576,931	$ 584,533
Stockholders' equity:
Nonvoting noncumulative preferred stock, par value	$ 0us-gaap_PreferredStockNoParValue	$ 0us-gaap_PreferredStockNoParValue
Nonvoting noncumulative preferred stock, authorized shares	100,000us-gaap_PreferredStockSharesAuthorized	100,000us-gaap_PreferredStockSharesAuthorized
Nonvoting noncumulative preferred stock, issued shares	0us-gaap_PreferredStockSharesIssued	0us-gaap_PreferredStockSharesIssued
Nonvoting noncumulative preferred stock, outstanding shares	0us-gaap_PreferredStockSharesOutstanding	0us-gaap_PreferredStockSharesOutstanding

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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Face amount per share of no-par value preferred stock nonredeemable or redeemable solely at the option of the issuer.

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