Interest-bearing Time Deposits in Banks and Securities (Tables)

3 Months Ended

Mar. 31, 2013

Investments Debt And Equity Securities [Abstract]

Summary of Available-for-Sale and Held-to-Maturity Securities

A summary of available-for-sale and held-to-maturity securities follows (in thousands):

	March 31, 2013
	Amortized Cost Basis		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Estimated Fair Value
Securities available-for-sale:
U.S. Treasury securities	$	6,017	$	23	$	—		$	6,040
Obligations of U.S. government sponsored-enterprises and agencies		189,913		3,451		—			193,364
Obligations of states and political subdivisions		865,282		53,191		(558	)		917,915
Corporate bonds and other		111,669		5,553		—			117,222
Residential mortgage-backed securities		592,911		23,866		(213	)		616,564
Commercial mortgage-backed securities		106,898		1,408		(1,260	)		107,046
Total securities available-for-sale	$	1,872,690	$	87,492	$	(2,031	)	$	1,958,151
Securities held-to-maturity:
Obligations of states and political subdivisions	$	595	$	5	$	—		$	600
Residential mortgage-backed securities		308		12		—			320
Total debt securities held-to-maturity	$	903	$	17	$	—		$	920

	December 31, 2012
	Amortized Cost Basis		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Estimated Fair Value
Securities available-for-sale:
U.S. Treasury securities	$	6,042	$	48	$	—		$	6,090
Obligations of U.S. government sponsored-enterprises and agencies		219,420		4,060		—			223,480
Obligations of states and political subdivisions		786,278		57,541		(129	)		843,690
Corporate bonds and other		117,244		6,020		(73	)		123,191
Residential mortgage-backed securities		564,434		23,285		(443	)		587,276
Commercial mortgage-backed securities		33,819		1,739		(250	)		35,308
Total securities available-for-sale	$	1,727,237	$	92,693	$	(895	)	$	1,819,035
Securities held-to-maturity:
Obligations of states and political subdivisions	$	735	$	7	$	—		$	742
Residential mortgage-backed securities		294		11		—			305
Commercial mortgage-backed securities		32		1		—			33
Total debt securities held-to-maturity	$	1,061	$	19	$	—		$	1,080

Amortized Cost and Estimated Fair Value of Debt Securities

The amortized cost and estimated fair value of debt securities at March 31, 2013, by contractual and expected maturity, are shown below (in thousands):

	Available-for-Sale				Held-to-Maturity
	Amortized Cost Basis		Estimated Fair Value		Amortized Cost Basis		Estimated Fair Value
Due within one year	$	142,205	$	144,366	$	595	$	600
Due after one year through five years		509,641		532,461		—		—
Due after five years through ten years		495,789		530,064		—		—
Due after ten years		25,246		27,650		—		—
Mortgage-backed securities		699,809		723,610		308		320
Total	$	1,872,690	$	1,958,151	$	903	$	920

Continuous Unrealized-Loss Position of Available-For-Sale and Held-To-Maturity Securities

The following tables disclose, as of March 31, 2013 and December 31, 2012, the Company’s investment securities that have been in a continuous unrealized-loss position for less than 12 months and for 12 months or longer (in thousands):

	Less than 12 Months				12 Months or Longer				Total
March 31, 2013	Fair Value		Unrealized Loss		Fair Value		Unrealized Loss		Fair Value		Unrealized Loss
Obligations of states and political subdivisions	$	42,102	$	558	$	—	$	—	$	42,102	$	558
Residential mortgage-backed securities		8,664		9		14,885		204		23,549		213
Commercial mortgage-backed securities		38,472		1,260		—		—		38,472		1,260
Total	$	89,238	$	1,827	$	14,885	$	204	$	104,123	$	2,031
	Less than 12 Months				12 Months or Longer				Total
December 31, 2012	Fair Value		Unrealized Loss		Fair Value		Unrealized Loss		Fair Value		Unrealized Loss
Obligations of states and political subdivisions	$	36,480	$	129	$	—	$	—	$	36,480	$	129
Residential mortgage-backed securities		17,344		401		3,574		42		20,918		443
Commercial mortgage-backed securities		12,453		250		—		—		12,453		250
Corporate bonds and other		4,994		73		—		—		4,994		73
Total	$	71,271	$	853	$	3,574	$	42	$	74,845	$	895