5. Securities

Securities Available for Sale

This table provides detailed information about securities available for sale at June 30, 2016 and December 31, 2015 (in thousands):


			Gross		Gross
	Amortized		Unrealized		Unrealized			Fair
	Cost		Gains		Losses			Value
June 30, 2016
U.S. Treasury	$	362,766	$	576	$	(5	)	$	363,337
U.S. Agencies		421,149		507		(31	)		421,625
Mortgage-backed		3,553,661		53,444		(6,930	)		3,600,175
State and political subdivisions		2,257,535		48,687		(243	)		2,305,979
Corporates		80,044		85		(66	)		80,063

Total	$	6,675,155	$	103,299	$	(7,275	)	$	6,771,179


			Gross		Gross
	Amortized		Unrealized		Unrealized			Fair
	Cost		Gains		Losses			Value
December 31, 2015
U.S. Treasury	$	350,354	$	1	$	(576	)	$	349,779
U.S. Agencies		667,414		7		(1,032	)		666,389
Mortgage-backed		3,598,115		12,420		(38,089	)		3,572,446
State and political subdivisions		2,116,543		23,965		(2,095	)		2,138,413
Corporates		80,585		—		(663	)		79,922

Total	$	6,813,011	$	36,393	$	(42,455	)	$	6,806,949

The following table presents contractual maturity information for securities available for sale at June 30, 2016 (in thousands):


	Amortized		Fair
	Cost		Value
Due in 1 year or less	$	931,783	$	932,836
Due after 1 year through 5 years		1,118,929		1,136,979
Due after 5 years through 10 years		861,965		887,760
Due after 10 years		208,817		213,429

Total		3,121,494		3,171,004
Mortgage-backed securities		3,553,661		3,600,175

Total securities available for sale	$	6,675,155	$	6,771,179

Securities may be disposed of before contractual maturities due to sales by the Company or because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties.

For the six months ended June 30, 2016, proceeds from the sales of securities available for sale were $598.7 million compared to $705.2 million for the same period in 2015. Securities transactions resulted in gross realized gains of $5.5 million and $8.4 million for the six months ended June 30, 2016 and 2015, respectively. The gross realized losses for the six months ended June 30, 2015 were $48 thousand.

Securities available for sale with a market value of $5.5 billion at June 30, 2016 and $5.9 billion at December 31, 2015 were pledged to secure U.S. Government deposits, other public deposits, and certain trust deposits as required by law. Of this amount, securities with a market value of $1.5 billion at June 30, 2016 and $1.6 billion at December 31, 2015 were pledged at the Federal Reserve Discount Window but were unencumbered as of those dates.

The following table shows the Company’s available for sale investments’ gross unrealized losses and fair value, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position, at June 30, 2016 and December 31, 2015 (in thousands):


June 30, 2016	Less than 12 months					12 months or more					Total
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
Description of Securities
U.S. Treasury	$	5,025	$	(5	)	$	—	$	—		$	5,025	$	(5	)
U.S. Agencies		45,635		(24	)		3,036		(7	)		48,671		(31	)
Mortgage-backed		204,221		(744	)		312,994		(6,186	)		517,215		(6,930	)
State and political subdivisions		131,455		(188	)		10,155		(55	)		141,610		(243	)
Corporates		8,748		(2	)		39,069		(64	)		47,817		(66	)

Total temporarily-impaired debt securities available for sale	$	395,084	$	(963	)	$	365,254	$	(6,312	)	$	760,338	$	(7,275	)


December 31, 2015	Less than 12 months					12 months or more					Total
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
Description of Securities
U.S. Treasury	$	344,556	$	(576	)	$	—	$	—		$	344,556	$	(576	)
U.S. Agencies		615,993		(1,032	)		—		—			615,993		(1,032	)
Mortgage-backed		2,056,316		(21,013	)		426,959		(17,076	)		2,483,275		(38,089	)
State and political subdivisions		479,197		(1,316	)		60,324		(779	)		539,521		(2,095	)
Corporates		29,126		(183	)		50,796		(480	)		79,922		(663	)

Total temporarily-impaired debt securities available for sale	$	3,525,188	$	(24,120	)	$	538,079	$	(18,335	)	$	4,063,267	$	(42,455	)

The unrealized losses in the Company’s investments in U.S. treasury obligations, U.S. government agencies, Government Sponsored Entity (GSE) mortgage-backed securities, municipal securities, and corporates were caused by changes in interest rates. The Company does not have the intent to sell these securities and does not believe it is more likely than not that the Company will be required to sell these securities before a recovery of amortized cost. The Company expects to recover its cost basis in the securities and does not consider these investments to be other-than-temporarily impaired at June 30, 2016.

Securities Held to Maturity

The table below provides detailed information for securities held to maturity at June 30, 2016 and December 31, 2015 (in thousands):


			Net
	Amortized		Unrealized		Fair
	Cost		Gains		Value
June 30, 2016
State and political subdivisions	$	880,600	$	111,115	$	991,715

December 31, 2015
State and political subdivisions	$	667,106	$	24,273	$	691,379

The following table presents contractual maturity information for securities held to maturity at June 30, 2016 (in thousands):


	Amortized		Fair
	Cost		Value
Due in 1 year or less	$	16,268	$	18,321
Due after 1 year through 5 years		76,310		85,939
Due after 5 years through 10 years		481,148		541,859
Due after 10 years		306,874		345,596

Total securities held to maturity	$	880,600	$	991,715

Expected maturities will differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties.

There were no sales of securities held to maturity during the six months ended June 30, 2016 or 2015.

Trading Securities

The net unrealized gains on trading securities at June 30, 2016 and June 30, 2015 were $93 thousand and $156 thousand, respectively, and were included in trading and investment banking income on the Consolidated Statements of Income.

Other Securities

The table below provides detailed information for Federal Reserve Bank (FRB) stock and Federal Home Loan Bank (FHLB) stock and other securities at June 30, 2016 and December 31, 2015 (in thousands):


			Gross		Gross
	Amortized		Unrealized		Unrealized			Fair
	Cost		Gains		Losses			Value
June 30, 2016
FRB and FHLB stock	$	33,667	$	—	$	—		$	33,667
Other securities – marketable		4		7,951		—			7,955
Other securities – non-marketable		23,974		730		(26	)		24,678

Total Other securities	$	57,645	$	8,681	$	(26	)	$	66,300

December 31, 2015
FRB and FHLB stock	$	33,215	$	—	$	—		$	33,215
Other securities – marketable		5		7,159		—			7,164
Other securities – non-marketable		23,855		964		—			24,819

Total Other securities	$	57,075	$	8,123	$	—		$	65,198

Investment in FRB stock is based on the capital structure of the investing bank, and investment in FHLB stock is mainly tied to the level of borrowings from the FHLB. These holdings are carried at cost. Other marketable and non-marketable securities include Prairie Capital Management (PCM) alternative investments in hedge funds and private equity funds, which are accounted for as equity-method investments. The fair value of other marketable securities includes alternative investment securities of $8.0 million at June 30, 2016 and $7.2 million at December 31, 2015. The fair value of other non-marketable securities includes alternative investment securities of $1.9 million at June 30, 2016 and $2.0 million at December 31, 2015. Unrealized gains or losses on alternative investments are recognized in the Equity earnings on alternative investments line of the Company’s Consolidated Statements of Income.