Consolidated Balance Sheets (unaudited) (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Assets
Securities held to maturity fair value	$ 461,224	$ 454,994
Stockholders' equity
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	2,500,000us-gaap_PreferredStockSharesAuthorized	2,500,000us-gaap_PreferredStockSharesAuthorized
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	100,000,000us-gaap_CommonStockSharesAuthorized	100,000,000us-gaap_CommonStockSharesAuthorized
Common stock, shares issued (in shares)	49,651,494us-gaap_CommonStockSharesIssued	49,651,494us-gaap_CommonStockSharesIssued
Common stock in treasury, at cost (in shares)	5,674,678us-gaap_TreasuryStockShares	5,755,040us-gaap_TreasuryStockShares

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