Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Investment securities [Abstract]
Investment securities, fair value	$ 673,626	$ 687,127
Real estate and other repossessed assets, allowance	$ 22,937	$ 24,195
Shareholders' equity: [Abstract]
Common stock, par value (in dollars per share)	$ 0.00006	$ 0.00006
Common stock, authorized (in shares)	2,500,000,000us-gaap_CommonStockSharesAuthorized	2,500,000,000us-gaap_CommonStockSharesAuthorized
Common stock, shares issued (in shares)	74,003,754us-gaap_CommonStockSharesIssued	73,163,275us-gaap_CommonStockSharesIssued
Common stock, shares outstanding (in shares)	74,003,754us-gaap_CommonStockSharesOutstanding	73,163,275us-gaap_CommonStockSharesOutstanding
Treasury stock, shares at cost (in shares)	4,890,018us-gaap_TreasuryStockShares	4,304,782us-gaap_TreasuryStockShares

Face amount or stated value per share of common stock.

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