Securities (Tables)

6 Months Ended

Jun. 30, 2012

Securities [Abstract]

Schedule of fair value and amortized cost of available-for-sale and held-to-maturity Securities

	June 30, 2012									December 31, 2011
(unaudited, in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Available-for-sale
Other government agencies	$	95,897	$	348	$	(175	)	$	96,070	$	197,898	$	834	$	(12	)	$	198,720
Residential mortgage-backed securities and collateralized mortgage obligations of government agencies		707,814		8,400		(488	)		715,726		579,430		9,244		(582	)		588,092
Obligations of state and political subdivisions		158,105		9,139		(63	)		167,181		171,782		8,664		(13	)		180,433
Corporate debt securities		38,745		276		(451	)		38,570		45,002		107		(1,043	)		44,066
Total debt securities	$	1,000,561	$	18,163	$	(1,177	)	$	1,017,547	$	994,112	$	18,849	$	(1,650	)	$	1,011,311
Equity securities		4,747		830		—			5,577		4,179		851		(1	)		5,029
Total available-for-sale securities	$	1,005,308	$	18,993	$	(1,177	)	$	1,023,124	$	998,291	$	19,700	$	(1,651	)	$	1,016,340
Held-to-maturity
Residential mortgage-backed securities and collateralized mortgage obligations of government agencies	$	198,870	$	7,444	$	(58	)	$	206,256	$	247,938	$	7,223	$	(87	)	$	255,074
Other residential collateralized mortgage obligations		451		11		—			462		783		9		(1	)		791
Obligations of state and political subdivisions		373,350		27,473		(509	)		400,314		342,752		21,459		(138	)		364,073
Corporate debt securities		—		—		—			—		1,452		82		—			1,534
Total held-to-maturity securities	$	572,671	$	34,928	$	(567	)	$	607,032	$	592,925	$	28,773	$	(226	)	$	621,472
Total securities	$	1,577,979	$	53,921	$	(1,744	)	$	1,630,156	$	1,591,216	$	48,473	$	(1,877	)	$	1,637,812

Schedule of Fair Value of Available-for-Sale and Held-To-Maturity Securities by Contractual Maturity

	June 30, 2012
(unaudited, in thousands)	One Year or less		One to Five Years		Five to Ten Years		After Ten Years		Mortgage-backed and Equity		Total
Available-for-sale
Other government agencies	$	2,571	$	15,104	$	40,790	$	37,605	$	—	$	96,070
Residential mortgage-backed securities and collateralized mortgage obligations of government agencies (1)		—		—		—		—		715,726		715,726
Obligations of states and political subdivisions		5,446		47,937		58,109		55,689		—		167,181
Corporate debt securities		3,253		30,474		1,886		2,957		—		38,570
Equity securities (3)		—		—		—		—		5,577		5,577
Total available-for-sale securities	$	11,270	$	93,515	$	100,785	$	96,251	$	721,303	$	1,023,124
Held-to-maturity (2)
Residential mortgage-backed securities and collateralized mortgage obligations of government agencies (1)	$	—	$	—	$	—	$	—	$	206,256	$	206,256
Other residential collateralized mortgage obligations (1)		—		—		—		—		462		462
Obligations of states and political subdivisions		1,177		7,840		57,128		334,169		—		400,314
Total held-to-maturity securities	$	1,177	$	7,840	$	57,128	$	334,169	$	206,718	$	607,032
Total securities	$	12,447	$	101,355	$	157,913	$	430,420	$	928,021	$	1,630,156

(1) Mortgage-backed and collateralized mortgage securities, which have prepayment provisions, are not assigned to maturity categories due to fluctuations in their prepayment speeds.

(2) The held-to-maturity portfolio is carried at an amortized cost of $572.7 million.

(3) Equity securities, which have no stated maturity, are not assigned a maturity category.

Schedule of Unrealized Losses on Investment Securities

	June 30, 2012
	Less than 12 months							12 months or more							Total
(unaudited, dollars in thousands)	Fair Value		Unrealized Losses			# of Securities		Fair Value		Unrealized Losses			# of Securities		Fair Value		Unrealized Losses			# of Securities
Other government agencies	$	38,077	$	(175	)		6	$	—	$	—			—	$	38,077	$	(175	)		6
Residential mortgage-backed securities and collateralized mortgage obligations of government agencies		128,008		(529	)		24		552		(17	)		1		128,560		(546	)		25
Obligations of states and political subdivisions		40,560		(572	)		59		—		—			—		40,560		(572	)		59
Corporate debt securities		7,985		(96	)		4		11,645		(355	)		4		19,630		(451	)		8
Total temporarily impaired securities	$	214,630	$	(1,372	)		93	$	12,197	$	(372	)		5	$	226,827	$	(1,744	)		98

	December 31, 2011
	Less than 12 months							12 months or more							Total
(unaudited, dollars in thousands)	Fair Value		Unrealized Losses			# of Securities		Fair Value		Unrealized Losses			# of Securities		Fair Value		Unrealized Losses			# of Securities
Other government agencies	$	24,486	$	(12	)		7	$	—	$	—			—	$	24,486	$	(12	)		7
Residential mortgage-backed securities and collateralized mortgage obligations of government agencies		133,106		(646	)		34		795		(23	)		2		133,901		(669	)		36
Other residential collateralized mortgage obligations		185		(1	)		1		—		—			—		185		(1	)		1
Obligations of states and political subdivisions		14,443		(146	)		20		1,902		(5	)		4		16,345		(151	)		24
Corporate debt securities		19,763		(145	)		11		13,103		(898	)		5		32,866		(1,043	)		16
Equity securities		4		(1	)		2		—		—			—		4		(1	)		2
Total temporarily impaired securities	$	191,987	$	(951	)		75	$	15,800	$	(926	)		11	$	207,787	$	(1,877	)		86