The following tables are a summary of the available-for-sale securities portfolio as of the dates shown:

		$000,000		$000,000		$000,000			$000,000
	September 30, 2011
(Dollars in thousands)	Amortized Cost		Gross unrealized gains		Gross unrealized losses			Fair Value
U.S. Treasury	$	16,034	$	169	$	—		$	16,203
U.S. Government agencies		682,221		4,959		(224	)		686,956
Municipal		61,146		1,179		(18	)		62,307
Corporate notes and other:
Financial issuers		160,341		2,440		(4,638	)		158,143
Other		28,221		332		(59	)		28,494
Mortgage-backed: ⁽¹⁾
Agency		226,423		13,638		(1	)		240,060
Non-agency CMOs		32,182		312		(7	)		32,487
Other equity securities		42,983		109		(60	)		43,032

Total available-for-sale securities	$	1,249,551	$	23,138	$	(5,007	)	$	1,267,682

		$000,000		$000,000		$000,000			$000,000
	December 31, 2010
(Dollars in thousands)	Amortized Cost		Gross unrealized gains		Gross unrealized losses			Fair Value
U.S. Treasury	$	104,418	$	—	$	(8,321	)	$	96,097
U.S. Government agencies		882,095		2,682		(722	)		884,055
Municipal		51,493		896		(86	)		52,303
Corporate notes and other:
Financial issuers		186,931		3,048		(2,972	)		187,007
Other		74,629		330		(51	)		74,908
Mortgage-backed: ⁽¹⁾
Agency		148,693		9,963		(3	)		158,653
Non-agency CMOs		3,018		10		—			3,028
Other equity securities		40,636		96		(481	)		40,251

Total available-for-sale securities	$	1,491,913	$	17,025	$	(12,636	)	$	1,496,302

(1)

Consisting entirely of residential mortgage-backed securities, none of which are subprime.

The following table presents the portion of the Company's available-for-sale securities portfolio which has gross unrealized losses, reflecting the length of time that individual securities have been in a continuous unrealized loss position at September 30, 2011:

The Company conducts a regular assessment of its investment securities to determine whether securities are other-than-temporarily impaired considering, among other factors, the nature of the securities, credit ratings or financial condition of the issuer, the extent and duration of the unrealized loss, expected cash flows, market conditions and the Company's ability to hold the securities through the anticipated recovery period.

The Company does not consider securities with unrealized losses at September 30, 2011 to be other-than-temporarily impaired. The Company does not intend to sell these investments and it is more likely than not that the Company will not be required to sell these investments before recovery of the amortized cost bases, which may be the maturity dates of the securities. The unrealized losses within each category have occurred as a result of changes in interest rates, market spreads and market conditions subsequent to purchase. Securities with continuous unrealized losses existing for more than twelve months were primarily corporate securities of financial issuers. The corporate securities of financial issuers in this category were comprised of three trust-preferred securities with high investment grades. These obligations have interest rates significantly below the rates at which these types of obligations are currently issued, and have maturity dates in 2027. Although they are currently callable by the issuers, it is unlikely that they will be called in the near future as the interest rates are very attractive to the issuers. A review of the issuers indicated that they have recently raised equity capital and/or have strong capital ratios. The Company does not own any pooled trust-preferred securities.

The following table provides information as to the amount of gross gains and gross losses realized and proceeds received through the sales of available-for-sale investment securities:

The amortized cost and fair value of securities as of September 30, 2011 and December 31, 2010, by contractual maturity, are shown in the following table. Contractual maturities may differ from actual maturities as borrowers may have the right to call or repay obligations with or without call or prepayment penalties. Mortgage-backed securities are not included in the maturity categories in the following maturity summary as actual maturities may differ from contractual maturities because the underlying mortgages may be called or prepaid without penalties:

At September 30, 2011 and December 31, 2010, securities having a carrying value of $1.1 billion and $876 million, respectively, which include securities traded but not yet settled, were pledged as collateral for public deposits, trust deposits, FHLB advances, securities sold under repurchase agreements and derivatives. At September 30, 2011, there were no securities of a single issuer, other than U.S. Government-sponsored agency securities, which exceeded 10% of shareholders' equity.