Securities (Tables)

6 Months Ended

Jun. 30, 2014

Investments, Debt and Equity Securities [Abstract]

Amortized Cost and Estimated Fair Value of Securities, Excluding Trading Securities

A summary of the amortized cost and estimated fair value of securities, excluding trading securities, is presented below.

	June 30, 2014								December 31, 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	$	248,797	$	18,000	$	—	$	266,797	$	248,592	$	20,139	$	—	$	268,731
Residential mortgage-backed securities	9,330		91		—		9,421		9,674		89		143		9,620
States and political subdivisions	2,806,390		20,671		32,285		2,794,776		2,880,482		7,691		137,861		2,750,312
Other	1,350		—		—		1,350		1,000		—		—		1,000
Total	$	3,065,867	$	38,762	$	32,285	$	3,072,344	$	3,139,748	$	27,919	$	138,004	$	3,029,663
Available for Sale
U.S. Treasury	$	2,449,708	$	19,080	$	20	$	2,468,768	$	2,522,159	$	18,395	$	—	$	2,540,554
U.S. Government agencies/corporations	—		—		—		—		54,024		—		44		53,980
Residential mortgage-backed securities	1,514,030		77,194		663		1,590,561		1,710,664		66,791		1,439		1,776,016
States and political subdivisions	2,153,351		67,502		251		2,220,602		1,476,316		20,090		7,492		1,488,914
Other	43,012		—		—		43,012		35,972		—		—		35,972
Total	$	6,160,101	$	163,776	$	934	$	6,322,943	$	5,799,135	$	105,276	$	8,975	$	5,895,436

Securities, with Unrealized Losses Segregated by Length of Impairment

As of June 30, 2014, 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
Held to Maturity
Residential mortgage-backed securities	$	—	$	—	$	—	$	—	$	—	$	—
States and political subdivisions	200,820		828		1,410,468		31,457		1,611,288		32,285
Total	$	200,820	$	828	$	1,410,468	$	31,457	$	1,611,288	$	32,285
Available for Sale
U.S. Treasury	$	150,176	$	20	$	—	$	—	$	150,176	$	20
Residential mortgage-backed securities	5,384		12		17,509		651		22,893		663
States and political subdivisions	63,962		213		5,378		38		69,340		251
Total	$	219,522	$	245	$	22,887	$	689	$	242,409	$	934

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 June 30, 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	$	168,070	$	170,552	$	803,553	$	809,751
Due after one year through five years	463,083		489,871		1,537,991		1,551,000
Due after five years through ten years	155,173		153,605		1,266,080		1,291,383
Due after ten years	2,270,211		2,248,895		995,435		1,037,236
Residential mortgage-backed securities	9,330		9,421		1,514,030		1,590,561
Equity securities	—		—		43,012		43,012
Total	$	3,065,867	$	3,072,344	$	6,160,101	$	6,322,943

Sales of Securities Available for Sale

Sales of securities available for sale were as follows:

	Three Months Ended   June 30,						Six Months Ended   June 30,
	2014			2013			2014			2013
Proceeds from sales	$	2,028		$	3,997,485		$	2,028		$	8,495,587
Gross realized gains	3			6			3			11
Gross realized losses	(1		)	—			(1		)	—
Tax (expense) benefit of securities gains/losses	(1		)	(2		)	(1		)	(4		)

Trading Account Securities, at Estimated Fair Value

Trading account securities, at estimated fair value, were as follows:

	June 30, 2014		December 31, 2013
U.S. Treasury	$	15,489	$	15,389
States and political subdivisions	—		1,009
Total	$	15,489	$	16,398

Net Gains and Losses on Trading Account Securities

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

	Three Months Ended   June 30,					Six Months Ended   June 30,
	2014		2013			2014			2013
Net gain on sales transactions	$	253	$	282		$	493		$	576
Net mark-to-market gains (losses)	—		(377		)	(3		)	(380		)
Net gain (loss) on trading account securities	$	253	$	(95	)	$	490		$	196