Investment Securities

9 Months Ended

Sep. 30, 2011

Investment Securities [Abstract]

Investment Securities

(2) Investment Securities

The amortized cost and approximate fair values of investment securities are summarized as follows:

Available-for-Sale September 30, 2011	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Obligations of U.S. government agencies	$	1,006,051	$	7,112	$	(71	)	$	1,013,092
U.S. agency residential mortgage-backed securities		848,075		34,535		(100	)		882,510
Private residential mortgage-backed securities		797		8		(22	)		783
Total	$	1,854,923	$	41,655	$	(193	)	$	1,896,385

Held-to-Maturity September 30, 2011	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
State, county and municipal securities	$	149,235	$	8,269	$	(41	)	$	157,463
Other securities		176		—		—			176
Total	$	149,411	$	8,269	$	(41	)	$	157,639

Available-for-Sale December 31, 2010	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Obligations of U.S. government agencies	$	956,017	$	3,337	$	(5,934	)	$	953,420
U.S. agency residential mortgage-backed securities		812,372		24,107		(4,619	)		831,860
Private residential mortgage-backed securities		1,057		10		(12	)		1,055
Total	$	1,769,446	$	27,454	$	(10,565	)	$	1,786,335

Held-to-Maturity December 31, 2010	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
State, county and municipal securities	$	146,850	$	1,375	$	(1,935	)	$	146,290
Other securities		218		—		—			218
Total	$	147,068	$	1,375	$	(1,935	)	$	146,508

Gross gains of $38 and $69 were realized on the disposition of available-for-sale investment securities during the three months ended September 30, 2011 and 2010, respectively. Gross gains of $56 and $111 were realized on the disposition of available-for-sale investment securities during the nine months ended September 30, 2011 and 2010, respectively. Gross losses of $0 and $3 were realized on the disposition of available-for-sale investment securities during the three and nine months ended September 30, 2011 or 2010, respectively.

The following table shows the gross unrealized losses and fair values of investment securities, aggregated by investment category, and the length of time individual investment securities have been in a continuous unrealized loss position, as of September 30, 2011 and December 31, 2010.

	Less than 12 Months					12 Months or More					Total
September 30, 2011	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses
Available-for-Sale
Obligations of U.S. government agencies	$	46,896	$	(71	)	$	—	$	—		$	46,896	$	(71	)
U.S. agency residential mortgage-backed securities		17,300		(100	)		—		—			17,300		(100	)
Private residential mortgage-backed securities		250		(14	)		187		(8	)		437		(22	)
Total	$	64,446	$	(185	)	$	187	$	(8	)	$	64,633	$	(193	)
	Less than 12 Months					12 Months or More					Total
September 30, 2011	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized L.osses
Held-to-Maturity
State, county and municipal securities	$	—	$	—		$	3,517	$	(41	)	$	3,517	$	(41	)
	Less than 12 Months					12 Months or More					Total
December 31, 2010	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses
Available-for-Sale
Obligations of U.S. government agencies	$	498,344	$	(5,934	)	$	—	$	—		$	498,344	$	(5,934	)
U.S. agency residential mortgage-backed securities		160,161		(4,619	)		—		—			160,161		(4,619	)
Private residential mortgage-backed securities		—		—			249		(12	)		249		(12	)
Total	$	658,505	$	(10,553	)	$	249	$	(12	)	$	658,754	$	(10,565	)
	Less than 12 Months					12 Months or More					Total
December 31, 2010	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses
Held-to-Maturity
State, county and municipal securities	$	42,178	$	(1,814	)	$	3,023	$	(121	)	$	45,201	$	(1,935	)

The investment portfolio is evaluated quarterly for other-than-temporary declines in the market value of each individual investment security. The Company had 13 and 128 individual investment securities that were in an unrealized loss position as of September 30, 2011 and December 31, 2010, respectively. Unrealized losses as of September 30, 2011 and December 31, 2010 related primarily to fluctuations in the current interest rates. The Company does not have the intent to sell any of the available-for-sale securities in the above table and it is more likely than not that the Company will not be required to sell any such securities before a recovery of cost. No impairment losses were recorded during the three or nine months ended September 30, 2011 or 2010.

Maturities of investment securities at September 30, 2011 are shown below. Maturities of mortgage-backed securities have been adjusted to reflect shorter maturities based upon estimated prepayments of principal. All other investment securities maturities are shown at contractual maturity dates.

	Available-for-Sale				Held-to-Maturity
September 30, 2011	Amortized Cost		Estimated Fair Value		Amortized Cost		Estimated Fair Value
Within one year	$	334,816	$	343,657	$	5,509	$	5,226
After one year but within five years		1,241,788		1,264,013		26,447		27,270
After five years but within ten years		181,081		187,534		55,712		59,282
After ten years		97,238		101,181		61,567		65,685
Total		1,854,923		1,896,385		149,235		157,463
Investments with no stated maturity		—		—		176		176
Total	$	1,854,923	$	1,896,385	$	149,411	$	157,639