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

9 Months Ended

Sep. 30, 2015

Cash and Cash Equivalents [Abstract]

Summary of Available-for-Sale Securities

A summary of the Company’s available-for-sale securities follows (in thousands):

	September 30, 2015
	Amortized Cost Basis		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Estimated Fair Value
U.S. Treasury securities	$	10,828	$	89	$	—		$	10,917
Obligations of U.S. government sponsored enterprises and agencies		153,960		1,237		—			155,197
Obligations of states and political subdivisions		1,375,958		62,005		(812	)		1,437,151
Corporate bonds and other		88,927		2,382		—			91,309
Residential mortgage-backed securities		817,791		16,566		(1,498	)		832,859
Commercial mortgage-backed securities		207,778		2,175		(33	)		209,920
Total securities available-for-sale	$	2,655,242	$	84,454	$	(2,343	)	$	2,737,353

	September 30, 2014
	Amortized Cost Basis		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Estimated Fair Value
U.S. Treasury securities	$	520	$	—	$	—		$	520
Obligations of U.S. government sponsored enterprises and agencies		106,339		964		(2	)		107,301
Obligations of states and political subdivisions		1,046,148		56,398		(577	)		1,101,969
Corporate bonds and other		96,424		3,269		—			99,693
Residential mortgage-backed securities		803,072		14,395		(5,600	)		811,867
Commercial mortgage-backed securities		134,769		31		(2,388	)		132,412
Total securities available-for-sale	$	2,187,272	$	75,057	$	(8,567	)	$	2,253,762

	December 31, 2014
	Amortized Cost Basis		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Estimated Fair Value
U.S. Treasury securities	$	518	$	2	$	—		$	520
Obligations of U.S. government sponsored enterprises and agencies		128,919		864		(28	)		129,755
Obligations of states and political subdivisions		1,107,795		60,083		(250	)		1,167,628
Corporate bonds and other		95,864		2,894		—			98,758
Residential mortgage-backed securities		871,265		16,804		(2,858	)		885,211
Commercial mortgage-backed securities		134,322		555		(893	)		133,984
Total securities available-for-sale	$	2,338,683	$	81,202	$	(4,029	)	$	2,415,856

Amortized Cost and Estimated Fair Value of Available-for-Sale Securities

The amortized cost and estimated fair value of available-for-sale securities at September 30, 2015, by contractual and expected maturity, are shown below (in thousands):

	Amortized Cost Basis		Estimated Fair Value
Due within one year	$	134,596	$	135,906
Due after one year through five years		751,592		786,916
Due after five years through ten years		739,704		767,254
Due after ten years		3,781		4,498
Mortgage-backed securities		1,025,569		1,042,779
Total	$	2,655,242	$	2,737,353

Continuous Unrealized-Loss Position of Available-for-Sale Securities

The following tables disclose, as of September 30, 2015 and 2014, and December 31, 2014, the Company’s investment securities that have been in a continuous unrealized-loss position for less than 12 months and for 12 or more months (in thousands):

	Less than 12 Months				12 Months or Longer				Total
September 30, 2015	Fair Value		Unrealized Loss		Fair Value		Unrealized Loss		Fair Value		Unrealized Loss
Obligations of states and political subdivisions	$	97,670	$	792	$	2,233	$	20	$	99,903	$	812
Residential mortgage-backed securities		62,765		396		65,614		1,102		128,379		1,498
Commercial mortgage-backed securities		5,878		9		9,466		24		15,344		33
Total	$	166,313	$	1,197	$	77,313	$	1,146	$	243,626	$	2,343

	Less than 12 Months				12 Months or Longer				Total
September 30, 2014	Fair Value		Unrealized Loss		Fair Value		Unrealized Loss		Fair Value		Unrealized Loss
Obligations of U.S. Government sponsored enterprises and agencies	$	876	$	2	$	—	$	—	$	876	$	2
Obligations of states and political subdivisions		17,871		38		50,158		539		68,029		577
Residential mortgage-backed securities		82,382		450		134,271		5,150		216,653		5,600
Commercial mortgage-backed securities		6,435		15		102,353		2,373		108,788		2,388
Total	$	107,564	$	505	$	286,782	$	8,062	$	394,346	$	8,567

	Less than 12 Months				12 Months or Longer				Total
December 31, 2014	Fair Value		Unrealized Loss		Fair Value		Unrealized Loss		Fair Value		Unrealized Loss
Obligations of U.S. government sponsored enterprises and agencies	$	25,480	$	28	$	—	$	—	$	25,480	$	28
Obligations of states and political subdivisions		15,128		60		21,249		190		36,377		250
Residential mortgage-backed securities		76,350		148		128,368		2,710		204,718		2,858
Commercial mortgage-backed securities		48,399		273		55,065		620		103,464		893
Total	$	165,357	$	509	$	204,682	$	3,520	$	370,039	$	4,029