Investments (Tables)

9 Months Ended

Sep. 30, 2012

Investments [Abstract]

Aggregate Values And Unrealized Gains And Losses Of Investment Securities

The aggregate values of investment securities at September 30, 2012, December 31, 2011, and September 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
September 30, 2012
U. S. Treasury	$	872,411	$	409	$	30	$	872,790
Government agency	2,656,974		3,851		78		2,660,747
Corporate bonds	50,826		243		—		51,069
Residential mortgage-backed securities	1,387,482		20,622		333		1,407,771
Equity securities	841		18,215		—		19,056
State, county and municipal	601		7		—		608
Total investment securities available for sale	$	4,969,135	$	43,347	$	441	$	5,012,041
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
September 30, 2011
U. S. Treasury	$	986,507	$	1,427	$	—	$	987,934
Government agency	2,261,000		2,344		2,435		2,260,909
Corporate bonds	401,048		3,595		—		404,643
Residential mortgage-backed securities	315,474		8,916		198		324,192
Equity securities	939		15,165		—		16,104
State, county and municipal	1,027		16		—		1,043
Total investment securities available for sale	$	3,965,995	$	31,463	$	2,633	$	3,994,825
Investment securities held to maturity
September 30, 2012
Residential mortgage-backed securities	$	1,459	$	151	$	27	$	1,583
December 31, 2011
Residential mortgage-backed securities	$	1,822	$	184	$	26	$	1,980
September 30, 2011
Residential mortgage-backed securities	$	1,943	$	191	$	26	$	2,108

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.

	September 30, 2012				December 31, 2011				September 30, 2011
	Cost		Fair value		Cost		Fair value		Cost		Fair value
Investment securities available for sale
Maturing in:
One year or less	$	2,206,157	$	2,207,677	$	3,238,657	$	3,241,415	$	3,398,267	$	3,401,530
One through five years	2,017,195		2,024,213		548,459		549,351		289,046		291,064
Five through 10 years	339,863		344,270		90,605		91,087		106,329		106,901
Over 10 years	405,079		416,825		151,198		159,257		171,414		179,226
Equity securities	841		19,056		939		15,313		939		16,104
Total investment securities available for sale	$	4,969,135	$	5,012,041	$	4,029,858	$	4,056,423	$	3,965,995	$	3,994,825
Investment securities held to maturity
Maturing in:
One through five years	$	1,354	$	1,440	$	12	$	11	$	13	$	12
Five through 10 years	19		11		1,699		1,820		1,816		1,940
Over 10 years	86		132		111		149		114		156
Total investment securities held to maturity	$	1,459	$	1,583	$	1,822	$	1,980	$	1,943	$	2,108

Securities Gains (Losses)

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

	Three months ended September 30					Nine months ended September 30
	2012		2011			2012			2011
Gross gains on sales of investment securities available for sale	$	31	$	375		$	36		$	531
Gross losses on sales of investment securities available for sale	—		(95		)	(2		)	(796		)
Other than temporary impairment loss on equity securities	—		(26		)	(45		)	(26		)
Total securities gains (losses)	$	31	$	254		$	(11	)	$	(291	)

Investment Securities With Unrealized Losses

The following table provides information regarding securities with unrealized losses as of September 30, 2012, December 31, 2011, and September 30, 2011:

	Less than 12 months				12 months or more				Total
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
September 30, 2012
Investment securities available for sale:
U. S. Treasury	$	195,444	$	30	$	—	$	—	$	195,444	$	30
Government agency	135,927		78		502		—		136,429		78
Residential mortgage-backed securities	53,526		284		5,280		49		58,806		333
Total	$	384,897	$	392	$	5,782	$	49	$	390,679	$	441
Investment securities held to maturity:
Residential mortgage-backed securities	$	—	$	—	$	18	$	27	$	18	$	27
December 31, 2011
Investment securities available for sale:
U. S. Treasury	151,269		30		—		—		151,269		30
Government agency	1,336,763		1,512		—		—		1,336,763		1,512
Residential mortgage-backed securities	59,458		304		1,380		42		60,838		346
State, county and municipal	—		—		10		1		10		1
Total	$	1,547,490	$	1,846	$	1,390	$	43	$	1,548,880	$	1,889
Investment securities held to maturity:
Residential mortgage-backed securities	$	—	$	—	$	21	$	26	$	21	$	26
September 30, 2011
Investment securities available for sale:
Government agency	$	1,051,017	$	2,435	—		$	—	$	1,051,017	$	2,435
Residential mortgage-backed securities	25,390		148		1,675		50		27,065		198
State, county and municipal	—		—		425		—		425		—
Total	$	1,076,407	$	2,583	$	2,100	$	50	$	1,078,507	$	2,633
Investment securities held to maturity:
Residential mortgage-backed securities	$	—	$	—	$	22	$	26	$	22	$	26