Investments (Tables)

6 Months Ended

Jun. 30, 2012

Investments [Abstract]

Aggregate Values And Unrealized Gains And Losses Of Investment Securities

The aggregate values of investment securities at June 30, 2012, December 31, 2011, and June 30, 2011 along with unrealized gains and losses determined on an individual security basis are as follows:

	Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Investment securities available for sale
June 30, 2012
U. S. Treasury	$	878,692	$	149	$	156	$	878,685
Government agency	2,976,079		2,684		565		2,978,198
Corporate bonds	49,987		459		—		50,446
Residential mortgage-backed securities	699,468		9,022		845		707,645
Equity securities	841		17,397		—		18,238
State, county and municipal	1,026		10		—		1,036
Total investment securities available for sale	$	4,606,093	$	29,721	$	1,566	$	4,634,248
December 31, 2011
U. S. Treasury	$	887,041	$	808	$	30	$	887,819
Government agency	2,591,974		1,747		1,512		2,592,209
Corporate bonds	250,476		2,344		—		252,820
Residential mortgage-backed securities	298,402		9,165		346		307,221
Equity securities	939		14,374		—		15,313
State, county and municipal	1,026		16		1		1,041
Total investment securities available for sale	$	4,029,858	$	28,454	$	1,889	$	4,056,423
June 30, 2011
U. S. Treasury	$	1,286,978	$	2,309	$	5	$	1,289,282
Government agency	1,904,135		1,848		1,140		1,904,843
Corporate bonds	461,756		5,258		43		466,971
Residential mortgage-backed securities	327,531		6,403		451		333,483
Equity securities	965		17,644		—		18,609
State, county and municipal	1,037		19		3		1,053
Total investment securities available for sale	$	3,982,402	$	33,481	$	1,642	$	4,014,241
Investment securities held to maturity
June 30, 2012
Residential mortgage-backed securities	$	1,578	$	163	$	27	$	1,714
December 31, 2011
Residential mortgage-backed securities	$	1,822	$	184	$	26	$	1,980
June 30, 2011
Residential mortgage-backed securities	$	2,098	$	206	$	26	$	2,278

Investment Securities Maturity Information

The following table provides the expected maturity distribution for residential mortgage-backed securities and the contractual maturity distribution of other investment securities as of the dates indicated. Callable securities are assumed to mature on their earliest call date.

	June 30, 2012				December 31, 2011				June 30, 2011
	Cost		Fair Value		Cost		Fair Value		Cost		Fair Value
Investment securities available for sale
Maturing in:
One year or less	$	2,424,304	$	2,425,612	$	3,238,657	$	3,241,415	$	3,133,235	$	3,140,002
One through five years	1,953,001		1,954,357		548,459		549,351		549,912		551,647
Five through 10 years	71,914		72,533		90,605		91,087		99,834		100,387
Over 10 years	156,033		163,508		151,198		159,257		198,456		203,596
Equity securities	841		18,238		939		15,313		965		18,609
Total investment securities available for sale	$	4,606,093	$	4,634,248	$	4,029,858	$	4,056,423	$	3,982,402	$	4,014,241
Investment securities held to maturity
Maturing in:
One through five years	$	1,470	$	1,568	$	12	$	11	$	8	$	6
Five through 10 years	4		4		1,699		1,820		1,973		2,110
Over 10 years	104		142		111		149		117		162
Total investment securities held to maturity	$	1,578	$	1,714	$	1,822	$	1,980	$	2,098	$	2,278

Securities Gains (Losses)

For each period presented, securities gains (losses) include the following:

	Three months ended June 30,						Six months ended June 30,
	2012			2011			2012			2011
Gross gains on sales of investment securities available for sale	$	5		$	—		$	5		$	156
Gross losses on sales of investment securities available for sale	(2		)	(96		)	(2		)	(701		)
Other than temporary impairment loss on equity securities	—			—			(45		)	—
Total securities gains (losses)	$	3		$	(96	)	$	(42	)	$	(545	)

Investment Securities With Unrealized Losses

The following table provides information regarding securities with unrealized losses as of June 30, 2012 and June 30, 2011:

	Less than 12 months				12 months or more				Total
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
June 30, 2012
Investment securities available for sale:
U. S. Treasury	$	528,579	$	156	$	—	$	—	$	528,579	$	156
Government agency	818,772		565		—		—		818,772		565
Residential mortgage-backed securities	292,053		808		1,668		37		293,721		845
State, county and municipal	—		—		10		—		10		—
Total	$	1,639,404	$	1,529	$	1,678	$	37	$	1,641,082	$	1,566
Investment securities held to maturity:
Residential mortgage-backed securities	$	—	$	—	$	19	$	27	$	19	$	27
June 30, 2011
Investment securities available for sale:
U.S. Treasury	$	50,307	$	5	$	—	$	—	$	50,307	$	5
Government agency	507,210		1,140		—		—		507,210		1,140
Corporate bonds	9,957		43		—		—		9,957		43
Residential mortgage-backed securities	80,866		401		2,016		50		82,882		451
State, county and municipal	529		3		10		—		539		3
Total	$	648,869	$	1,592	$	2,026	$	50	$	650,895	$	1,642
Investment securities held to maturity:
Residential mortgage-backed securities	$	—	$	—	$	29	$	26	$	29	$	26