Securities (Tables)

6 Months Ended

Jun. 30, 2011

Securities

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

	June 30, 2011								December 31, 2010
	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	$	247,606	$	19,581	$	—	$	267,187	$	247,421	$	13,517	$	—	$	260,938
Residential mortgage-backed securities		4,103		165		—		4,268		4,405		136		—		4,541
States and political subdivisions		97,288		1,577		345		98,520		30,803		—		1,054		29,749
Other		1,000		—		—		1,000		1,000		—		—		1,000
Total	$	349,997	$	21,323	$	345	$	370,975	$	283,629	$	13,653	$	1,054	$	296,228
Available for Sale:
U. S. Treasury	$	773,274	$	21,011	$	—	$	794,285	$	973,033	$	13,998	$	—	$	987,031
Residential mortgage-backed securities		2,356,226		128,439		2		2,484,663		1,989,299		103,018		987		2,091,330
States and political subdivisions		2,026,204		91,776		2,554		2,115,426		2,008,618		53,358		21,676		2,040,300
Other		37,980		—		—		37,980		38,809		—		—		38,809
Total	$	5,193,684	$	241,226	$	2,556	$	5,432,354	$	5,009,759	$	170,374	$	22,663	$	5,157,470

Securities, with Unrealized Losses Segregated by Length of Impairment

	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
States and political subdivisions	$	23,446	$	345	$	—	$	—	$	23,446	$	345
Total	$	23,446	$	345	$	—	$	—	$	23,446	$	345
Available for Sale
Residential mortgage-backed securities	$	352	$	2	$	—	$	—	$	352	$	2
States and political subdivisions		271,806		2,527		667		27		272,473		2,554
Total	$	272,158	$	2,529	$	667	$	27	$	272,825	$	2,556

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

	Held to Maturity				Available for Sale
	Amortized Cost		Estimated Fair Value		Amortized Cost		Estimated Fair Value
Due in one year or less	$	—	$	—	$	44,715	$	45,289
Due after one year through five years		1,000		1,000		829,948		854,447
Due after five years through ten years		250,953		270,674		172,958		182,651
Due after ten years		93,941		95,033		1,751,857		1,827,324
Residential mortgage-backed securities		4,103		4,268		2,356,226		2,484,663
Equity securities		—		—		37,980		37,980
Total	$	349,997	$	370,975	$	5,193,684	$	5,432,354

Sales of Securities Available for Sale

	Three Months Ended June 30,				Six Months Ended June 30,
	2011		2010		2011		2010
Proceeds from sales	$	845	$	2,999,251	$	5,548,386	$	9,997,994
Gross realized gains		—		1		9		8
Gross realized losses		—		—		4		2

Trading Account Securities, at Estimated Fair Value

	June 30, 2011		December 31, 2010
U.S. Treasury	$	14,517	$	14,986
States and political subdivisions		—		115
Total	$	14,517	$	15,101

Net Gains and Losses on Trading Account Securities

	Three Months Ended June 30,				Six Months Ended June  30,
	2011		2010		2011		2010
Net gain on sales transactions	$	161	$	398	$	469	$	880
Net mark-to-market gains		7		71		7		123
Net gain on trading account securities	$	168	$	469	$	476	$	1,003