Investments (Tables)

3 Months Ended

Mar. 31, 2013

Investments [Abstract]

Aggregate Values And Unrealized Gains And Losses Of Investment Securities

The aggregate values of investment securities at March 31, 2013, December 31, 2012, and March 31, 2012, 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
March 31, 2013
U. S. Treasury	$	749,284	$	474	$	1	$	749,757
Government agency	3,147,363		2,952		274		3,150,041
Residential mortgage-backed securities	1,348,765		10,849		1,512		1,358,102
Equity securities	543		19,860		—		20,403
State, county and municipal	546		1		—		547
Other	844		1		17		828
Total investment securities available for sale	$	5,247,345	$	34,137	$	1,804	$	5,279,678
December 31, 2012
U. S. Treasury	$	823,241	$	403	$	12	$	823,632
Government agency	3,052,040		3,501		337		3,055,204
Residential mortgage-backed securities	1,315,211		14,787		341		1,329,657
Equity securities	543		15,822		—		16,365
State, county and municipal	546		4		—		550
Other	838		—		18		820
Total investment securities available for sale	$	5,192,419	$	34,517	$	708	$	5,226,228
March 31, 2012
U. S. Treasury	$	1,065,035	$	306	$	305	$	1,065,036
Government agency	2,859,197		1,228		5,040		2,855,385
Corporate bonds	225,214		1,214		—		226,428
Residential mortgage-backed securities	282,706		8,393		191		290,908
Equity securities	894		18,049		—		18,943
State, county and municipal	1,026		14		1		1,039
Total investment securities available for sale	$	4,434,072	$	29,204	$	5,537	$	4,457,739
Investment securities held to maturity
March 31, 2013
Residential mortgage-backed securities	$	1,229	$	120	$	27	$	1,322
December 31, 2012
Residential mortgage-backed securities	$	1,342	$	133	$	27	$	1,448
March 31, 2012
Residential mortgage-backed securities	$	1,688	$	183	$	27	$	1,844

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.

	March 31, 2013				December 31, 2012				March 31, 2012
	Cost		Fair value		Cost		Fair value		Cost		Fair value
Investment securities available for sale
Maturing in:
One year or less	$	2,350,896	$	2,352,328	$	2,288,556	$	2,289,859	$	2,750,247	$	2,748,710
One through five years	2,233,407		2,237,530		2,323,222		2,329,207		1,469,876		1,469,236
Five through 10 years	181,370		182,281		194,398		196,371		67,229		67,683
Over 10 years	481,129		487,136		385,700		394,426		145,826		153,167
Equity securities	543		20,403		543		16,365		894		18,943
Total investment securities available for sale	$	5,247,345	$	5,279,678	$	5,192,419	$	5,226,228	$	4,434,072	$	4,457,739
Investment securities held to maturity
Maturing in:
One through five years	$	1,132	$	1,188	$	1,242	$	1,309	$	379	$	393
Five through 10 years	18		10		18		11		1,201		1,306
Over 10 years	79		124		82		128		108		145
Total investment securities held to maturity	$	1,229	$	1,322	$	1,342	$	1,448	$	1,688	$	1,844

Securities Gains (Losses)

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

	Three months ended March 31
	2013		2012
Gross gains on sales of investment securities available for sale	$	58	$	—
Gross losses on sales of investment securities available for sale	—		—
Other than temporary impairment loss on equity securities	—		(45		)
Total securities gains (losses)	$	58	$	(45	)

Investment Securities With Unrealized Losses

The following table provides information regarding securities with unrealized losses as of March 31, 2013, December 31, 2012, and March 31, 2012:

	Less than 12 months				12 months or more				Total
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
March 31, 2013
Investment securities available for sale:
U. S. Treasury	$	25,060	$	1	$	—	$	—	$	25,060	$	1
Government agency	548,618		274		—		—		548,618		274
Residential mortgage-backed securities	349,746		1,379		10,089		133		359,835		1,512
Other	828		17		—		—		828		17
Total	$	924,252	$	1,671	$	10,089	$	133	$	934,341	$	1,804
Investment securities held to maturity:
Residential mortgage-backed securities	$	—	$	—	$	16	$	27	$	16	$	27
December 31, 2012
Investment securities available for sale:
U. S. Treasury	$	120,045	$	12	$	—	$	—	$	120,045	$	12
Government agency	407,498		337		—		—		407,498		337
Residential mortgage-backed securities	135,880		214		9,433		127		145,313		341
Other	820		18		—		—		820		18
Total	$	664,243	$	581	$	9,433	$	127	$	673,676	$	708
Investment securities held to maturity:
Residential mortgage-backed securities	$	—	$	—	$	17	$	27	$	17	$	27
March 31, 2012
Investment securities available for sale:
U.S. Treasury	$	579,673	$	305	$	—	$	—	$	579,673	$	305
Government agency	2,143,742		5,040		—		—		2,143,742		5,040
Residential mortgage-backed securities	28,595		156		1,113		35		29,708		191
State, county and municipal	127		1		10		—		137		1
Total	$	2,752,137	$	5,502	$	1,123	$	35	$	2,753,260	$	5,537
Investment securities held to maturity:
Residential mortgage-backed securities	$	—	$	—	$	20	$	27	$	20	$	27