Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Securities held-to-maturity ,fair value	3,948,706	3,370,912
Preferred stock, par value	0.01	0.01
Preferred stock, shares authorized	3,000,000us-gaap_PreferredStockSharesAuthorized	3,000,000us-gaap_PreferredStockSharesAuthorized
Common stock par value	0.01	0.01
Common stock, shares authorized	200,000,000us-gaap_CommonStockSharesAuthorized	200,000,000us-gaap_CommonStockSharesAuthorized
Common stock, shares issued	93,623,090us-gaap_CommonStockSharesIssued	93,366,673us-gaap_CommonStockSharesIssued
Treasury stock ,shares	3,241,555us-gaap_TreasuryStockShares	3,407,256us-gaap_TreasuryStockShares
Series A Preferred Stock [Member]
Preferred stock, par value	0.01
Preferred stock, shares issued	28,939	28,939
Preferred stock, shares outstanding	28,939	28,939
Series E Preferred Stock [Member]
Preferred stock, shares issued	5,060	5,060
Preferred stock, shares outstanding	5,060	5,060

Face amount or stated value per share of common stock.

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