Note 2. Investment Securities, Available-for-Sale

A comparison of the amortized cost and estimated fair value of the Company’s investment securities designated as available-for-sale is presented below.



	September 30, 2013
	Weighted		Amortized		Gross Unrealized			Fair
(Dollars in thousands)	Yield		Cost		Gains	Losses		Value
U.S. government sponsored enterprises
Maturing after one year through five years	2.29	%	$	11,278	240	—		11,518
Maturing after five years through ten years	1.82	%	38		—	—		38
	2.29	%	11,316		240	—		11,556
State and local governments
Maturing within one year	2.18	%	6,059		52	—		6,111
Maturing after one year through five years	2.10	%	162,569		3,096	(431	)	165,234
Maturing after five years through ten years	3.17	%	57,892		1,122	(832	)	58,182
Maturing after ten years	4.46	%	1,104,890		28,571	(21,604	)	1,111,857
	4.10	%	1,331,410		32,841	(22,867	)	1,341,384
Corporate bonds
Maturing within one year	2.10	%	73,064		736	—		73,800
Maturing after one year through five years	2.10	%	358,034		2,890	(2,852	)	358,072
Maturing after five years through ten years	2.22	%	11,058		—	(85	)	10,973
	2.10	%	442,156		3,626	(2,937	)	442,845
Residential mortgage-backed securities	2.44	%	1,515,728		15,357	(7,917	)	1,523,168
Total investment securities	3.06	%	$	3,300,610	52,064	(33,721	)	3,318,953



	December 31, 2012
	Weighted		Amortized		Gross Unrealized			Fair
(Dollars in thousands)	Yield		Cost		Gains	Losses		Value
U.S. government and federal agency
Maturing within one year	1.62	%	$	201	1	—		202
U.S. government sponsored enterprises
Maturing after one year through five years	2.30	%	17,064		371	—		17,435
Maturing after five years through ten years	2.03	%	44		1	—		45
	2.29	%	17,108		372	—		17,480
State and local governments
Maturing within one year	2.01	%	4,288		28	(2	)	4,314
Maturing after one year through five years	2.11	%	149,497		4,142	(142	)	153,497
Maturing after five years through ten years	2.95	%	38,346		1,102	(99	)	39,349
Maturing after ten years	4.70	%	935,897		82,823	(1,362	)	1,017,358
	4.29	%	1,128,028		88,095	(1,605	)	1,214,518
Corporate bonds
Maturing within one year	1.73	%	18,412		51	—		18,463
Maturing after one year through five years	2.22	%	250,027		4,018	(238	)	253,807
Maturing after five years through ten years	2.23	%	16,144		381	—		16,525
	2.19	%	284,583		4,450	(238	)	288,795
Collateralized debt obligations
Maturing after ten years	8.03	%	1,708		—	—		1,708
Residential mortgage-backed securities	1.95	%	2,156,049		8,860	(4,607	)	2,160,302
Total investment securities	2.71	%	$	3,587,677	101,778	(6,450	)	3,683,005

Included in the residential mortgage-backed securities are $3,214,000 and $46,733,000 as of September 30, 2013 and December 31, 2012, respectively, of non-guaranteed private label whole loan mortgage-backed securities of which none of the underlying collateral is considered “subprime.”

Maturities of securities do not reflect repricing opportunities present in adjustable rate securities, nor do they reflect expected shorter maturities based upon early prepayment of principal. Weighted average yields are based on the interest method taking into account premium amortization, discount accretion and mortgage-backed securities’ prepayment provisions. Weighted average yields on tax-exempt investment securities exclude the federal income tax benefit.

The cost of each investment sold is determined by specific identification. Gain or loss on sale of investments consists of the following:



	Three Months ended				Nine Months ended
(Dollars in thousands)	September 30, 2013			September 30, 2012	September 30, 2013		September 30, 2012
Gross proceeds	$	102,483		—	181,971		—
Less amortized cost	(102,886		)	—	(182,270	)	—
Net loss on sale of investments	$	(403	)	—	(299	)	—
Gross gain on sale of investments	$	3,467		—	3,723		—
Gross loss on sale of investments	(3,870		)	—	(4,022	)	—
Net loss on sale of investments	$	(403	)	—	(299	)	—

Investments with an unrealized loss position are summarized as follows:



	September 30, 2013
	Less than 12 Months				12 Months or More			Total
(Dollars in thousands)	Fair Value		Unrealized Loss		Fair Value	Unrealized Loss		Fair Value	Unrealized Loss
State and local governments	$	405,834	(21,121	)	22,373	(1,746	)	428,207	(22,867	)
Corporate bonds	189,130		(2,937	)	—	—		189,130	(2,937	)
Residential mortgage-backed securities	446,642		(7,917	)	—	—		446,642	(7,917	)
Total temporarily impaired securities	$	1,041,606	(31,975	)	22,373	(1,746	)	1,063,979	(33,721	)



	December 31, 2012
	Less than 12 Months				12 Months or More			Total
(Dollars in thousands)	Fair Value		Unrealized Loss		Fair Value	Unrealized Loss		Fair Value	Unrealized Loss
State and local governments	$	102,896	(1,531	)	4,533	(74	)	107,429	(1,605	)
Corporate bonds	41,856		(238	)	—	—		41,856	(238	)
Residential mortgage-backed securities	955,235		(4,041	)	62,905	(566	)	1,018,140	(4,607	)
Total temporarily impaired securities	$	1,099,987	(5,810	)	67,438	(640	)	1,167,425	(6,450	)

With respect to the Company’s review of its securities in an unrealized loss position at September 30, 2013, management determined that it did not intend to sell and there was no expected requirement to sell any of its temporarily impaired securities. Based on an analysis of its impaired securities as of September 30, 2013 and December 31, 2012, the Company determined that none of such securities had other-than-temporary impairment.