Securities (Tables)

12 Months Ended

Dec. 31, 2014

Investments, Debt and Equity Securities [Abstract]

Year End Securities Held To Maturity And Available For Sale

Year-end securities held to maturity and available for sale consisted of the following:

	2014								2013
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
Held to Maturity:
U.S. Treasury	$	249,009	$	14,604	$	—	$	263,613	$	248,592	$	20,139	$	—	$	268,731
Residential mortgage-backed securities	8,012		92		—		8,104		9,674		89		143		9,620
States and political subdivisions	2,668,115		34,243		9,035		2,693,323		2,880,482		7,691		137,861		2,750,312
Other	1,350		—		—		1,350		1,000		—		—		1,000
Total	$	2,926,486	$	48,939	$	9,035	$	2,966,390	$	3,139,748	$	27,919	$	138,004	$	3,029,663
Available for Sale:
U. S. Treasury	$	3,783,899	$	30,594	$	3,241	$	3,811,252	$	2,522,159	$	18,395	$	—	$	2,540,554
U.S. government agencies/corporations	—		—		—		—		54,024		—		44		53,980
Residential mortgage-backed securities	1,331,114		68,027		417		1,398,724		1,710,664		66,791		1,439		1,776,016
States and political subdivisions	3,104,563		104,500		156		3,208,907		1,476,316		20,090		7,492		1,488,914
Other	42,371		—		—		42,371		35,972		—		—		35,972
Total	$	8,261,947	$	203,121	$	3,814	$	8,461,254	$	5,799,135	$	105,276	$	8,975	$	5,895,436

Year End Securities with Unrealized Losses, Segregated by Length of Impairment

Year-end securities with unrealized losses, segregated by length of impairment, were as follows:

	Less than 12 Months				More than 12 Months				Total
	Estimated Fair Value		Unrealized Losses		Estimated Fair Value		Unrealized Losses		Estimated Fair Value		Unrealized Losses
2014
Held to Maturity:
States and political subdivisions	$	68,024	$	144	$	683,251	$	8,891	$	751,275	$	9,035
Total	$	68,024	$	144	$	683,251	$	8,891	$	751,275	$	9,035
Available for Sale:
U.S. Treasury	$	1,019,230	$	3,241	$	—	$	—	$	1,019,230	$	3,241
Residential mortgage-backed securities	8,550		42		16,944		375		25,494		417
States and political subdivisions	65,751		156		—		—		65,751		156
Total	$	1,093,531	$	3,439	$	16,944	$	375	$	1,110,475	$	3,814
2013
Held to Maturity:
Residential mortgage-backed securities	$	6,934	$	143	$	—	$	—	$	6,934	$	143
States and political subdivisions	2,071,521		113,512		266,566		24,349		2,338,087		137,861
Total	$	2,078,455	$	113,655	$	266,566	$	24,349	$	2,345,021	$	138,004
Available for Sale:
U.S. government agencies/ corporations	$	53,980	$	44	$	—	$	—	$	53,980	$	44
Residential mortgage-backed securities	33,001		1,157		2,713		282		35,714		1,439
States and political subdivisions	679,923		7,492		—		—		679,923		7,492
Total	$	766,904	$	8,693	$	2,713	$	282	$	769,617	$	8,975

Amortized Cost and Estimated Fair Value of Securities, Excluding Trading Securities, Presented by Contractual Maturity

The amortized cost and estimated fair value of securities, excluding trading securities, at December 31, 2014 are presented below by contractual maturity. Expected maturities may differ from contractual maturities because issuers may have the right to call or prepay obligations. Residential mortgage-backed securities and equity securities are shown separately since they are not due at a single maturity date.

	Held to Maturity				Available for Sale
	Amortized Cost		Estimated Fair Value		Amortized Cost		Estimated Fair Value
Due in one year or less	$	153,701	$	155,505	$	515,567	$	517,482
Due after one year through five years	533,990		564,854		2,474,795		2,486,488
Due after five years through ten years	172,371		172,240		1,937,104		1,977,280
Due after ten years	2,058,412		2,065,687		1,960,996		2,038,909
Residential mortgage-backed securities	8,012		8,104		1,331,114		1,398,724
Equity securities	—		—		42,371		42,371
Total	$	2,926,486	$	2,966,390	$	8,261,947	$	8,461,254

Sales of Securities Available for Sale

Sales of securities available for sale were as follows:

	2014			2013			2012
Proceeds from sales	$	12,151,287		$	10,056,060		$	16,587,482
Gross realized gains	39			1,206			6,943
Gross realized losses	(1		)	(30		)	(2,629		)
Tax (expense) benefit of securities gains/losses	(13		)	(412		)	(1,510		)

Premium Amortization and Discount Accretion Included in Income on Securities [Table Text Block]

Premium amortization and discount accretion included in interest income on securities was as follows:

	2014			2013			2012
Premium amortization	$	(68,070	)	$	(49,112	)	$	(28,364	)
Discount accretion	6,802			7,191			6,663
Net (premium amortization) discount accretion	$	(61,268	)	$	(41,921	)	$	(21,701	)

Year End Trading Account Securities, at Estimated Fair Value

Year-end trading account securities, at estimated fair value, were as follows:

	2014		2013
U.S. Treasury	$	15,339	$	15,389
States and political subdivisions	87		1,009
Total	$	15,426	$	16,398

Net Gains and Losses on Trading Account Securities

Net gains and losses on trading account securities were as follows:

	2014		2013			2012
Net gain on sales transactions	$	829	$	878		$	1,219
Net mark-to-market gains (losses)	—		(429		)	(161		)
Net gain on trading account securities	$	829	$	449		$	1,058