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

9 Months Ended

Sep. 30, 2016

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, 2016
	Amortized Cost Basis		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Estimated Fair Value
U.S. Treasury securities	$	10,685	$	54	$	—		$	10,739
Obligations of U.S. government sponsored enterprises and agencies		114,918		802		—			115,720
Obligations of states and political subdivisions		1,419,737		83,694		(715	)		1,502,716
Corporate bonds and other		68,285		1,325		(1	)		69,609
Residential mortgage-backed securities		750,673		17,125		(1,299	)		766,499
Commercial mortgage-backed securities		259,636		4,200		(89	)		263,747
Total securities available-for-sale	$	2,623,934	$	107,200	$	(2,104	)	$	2,729,030

	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
	December 31, 2015
	Amortized Cost Basis		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Estimated Fair Value
U.S. Treasury securities	$	10,792	$	5	$	(2	)	$	10,795
Obligations of U.S. government sponsored enterprises and agencies		148,393		268		(107	)		148,554
Obligations of states and political subdivisions		1,379,879		71,382		(134	)		1,451,127
Corporate bonds and other		86,182		1,778		(5	)		87,955
Residential mortgage-backed securities		781,648		10,993		(3,759	)		788,882
Commercial mortgage-backed securities		247,991		429		(1,834	)		246,586
Total securities available-for-sale	$	2,654,885	$	84,855	$	(5,841	)	$	2,733,899

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, 2016, by contractual and expected maturity, are shown below (in thousands):

	Amortized Cost Basis		Estimated Fair Value
Due within one year	$	195,637	$	197,334
Due after one year through five years		675,403		710,096
Due after five years through ten years		740,541		788,744
Due after ten years		2,044		2,610
Mortgage-backed securities		1,010,309		1,030,246
Total	$	2,623,934	$	2,729,030

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

The following tables disclose, as of September 30, 2016 and 2015, and December 31, 2015, 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, 2016	Fair Value		Unrealized Loss		Fair Value		Unrealized Loss		Fair Value		Unrealized Loss
Obligations of states and political subdivisions	$	82,131	$	711	$	741	$	4	$	82,872	$	715
Corporate bonds and other		12,257		1		—		—		12,257		1
Residential mortgage-backed securities		80,015		267		57,334		1,032		137,349		1,299
Commercial mortgage-backed securities		10,213		25		13,692		64		23,905		89
Total	$	184,616	$	1,004	$	71,767	$	1,100	$	256,383	$	2,104
	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
December 31, 2015	Fair Value		Unrealized Loss		Fair Value		Unrealized Loss		Fair Value		Unrealized Loss
U.S. Treasury securities	$	5,110	$	2	$	—	$	—	$	5,110	$	2
Obligations of U.S. government sponsored enterprises and agencies		50,388		107		—		—		50,388		107
Obligations of states and political subdivisions		32,929		127		1,513		7		34,442		134
Corporate bonds and other		7,004		5		—		—		7,004		5
Residential mortgage-backed securities		231,481		1,765		63,919		1,994		295,400		3,759
Commercial mortgage-backed securities		196,163		1,752		9,345		82		205,508		1,834
Total	$	523,075	$	3,758	$	74,777	$	2,083	$	597,852	$	5,841