Securities Available for Sale and Held to Maturity (Tables)

12 Months Ended

Dec. 31, 2015

Investments Debt And Equity Securities [Abstract]

Amortized Cost and Estimated Fair Value of Available for Sale and Held to Maturity Securities

The following tables are a summary of the amortized cost and estimated fair value of securities available for sale and held to maturity at December 31, 2015 and 2014 ($ in thousands):

	Securities Available for Sale									Securities Held to Maturity
			Gross		Gross			Estimated				Gross		Gross			Estimated
	Amortized		Unrealized		Unrealized			Fair		Amortized		Unrealized		Unrealized			Fair
December 31, 2015	Cost		Gains		(Losses)			Value		Cost		Gains		(Losses)			Value
U.S. Government agency obligations
Issued by U.S. Government agencies	$	68,314	$	555	$	(734	)	$	68,135	$	—	$	—	$	—		$	—
Issued by U.S. Government sponsored agencies		258		23		—			281		101,782		3,282		—			105,064
Obligations of states and political subdivisions		134,719		3,922		(32	)		138,609		55,892		2,918		—			58,810
Mortgage-backed securities
Residential mortgage pass-through securities
Guaranteed by GNMA		25,602		399		(189	)		25,812		17,363		342		(49	)		17,656
Issued by FNMA and FHLMC		222,899		2,956		(313	)		225,542		10,368		311		—			10,679
Other residential mortgage-backed securities
Issued or guaranteed by FNMA, FHLMC or GNMA		1,584,338		9,541		(11,019	)		1,582,860		820,012		4,951		(4,742	)		820,221
Commercial mortgage-backed securities
Issued or guaranteed by FNMA, FHLMC or GNMA		278,429		2,689		(1,892	)		279,226		182,401		1,700		(1,164	)		182,937
Asset-backed securities and structured financial products		25,003		79		(125	)		24,957		—		—		—			—
Total	$	2,339,562	$	20,164	$	(14,304	)	$	2,345,422	$	1,187,818	$	13,504	$	(5,955	)	$	1,195,367

December 31, 2014
U.S. Treasury securities	$	100	$	—	$	—		$	100	$	—	$	—	$	—		$	—
U.S. Government agency obligations
Issued by U.S. Government agencies		79,788		694		(826	)		79,656		—		—		—			—
Issued by U.S. Government sponsored agencies		32,725		170		(77	)		32,818		100,971		2,631		—			103,602
Obligations of states and political subdivisions		157,001		5,325		(68	)		162,258		63,505		3,398		—			66,903
Mortgage-backed securities
Residential mortgage pass-through securities
Guaranteed by GNMA		11,897		544		(14	)		12,427		19,115		466		(16	)		19,565
Issued by FNMA and FHLMC		199,599		4,842		—			204,441		11,437		471		—			11,908
Other residential mortgage-backed securities
Issued or guaranteed by FNMA, FHLMC or GNMA		1,655,733		16,664		(10,564	)		1,661,833		834,176		6,440		(1,916	)		838,700
Commercial mortgage-backed securities
Issued or guaranteed by FNMA, FHLMC or GNMA		184,394		4,968		(28	)		189,334		141,481		1,750		(1,063	)		142,168
Asset-backed securities and structured financial products		30,776		924		—			31,700		—		—		—			—
Total	$	2,352,013	$	34,131	$	(11,577	)	$	2,374,567	$	1,170,685	$	15,156	$	(2,995	)	$	1,182,846

Securities with Gross Unrealized Losses, Segregated by Length of Impairment

The table below includes securities with gross unrealized losses segregated by length of impairment at December 31, 2015 and 2014 ($ in thousands):

	Less than 12 Months					12 Months or More					Total
			Gross					Gross					Gross
	Estimated		Unrealized			Estimated		Unrealized			Estimated		Unrealized
December 31, 2015	Fair Value		Losses			Fair Value		Losses			Fair Value		Losses
U.S. Government agency obligations
Issued by U.S. Government agencies	$	18,924	$	(81	)	$	30,591	$	(653	)	$	49,515	$	(734	)
Obligations of states and political subdivisions		4,289		(12	)		2,842		(20	)		7,131		(32	)
Mortgage-backed securities
Residential mortgage pass-through securities
Guaranteed by GNMA		20,300		(222	)		1,863		(16	)		22,163		(238	)
Issued by FNMA and FHLMC		82,177		(313	)		—		—			82,177		(313	)
Other residential mortgage-backed securities
Issued or guaranteed by FNMA, FHLMC or GNMA		1,135,533		(8,832	)		238,152		(6,929	)		1,373,685		(15,761	)
Commercial mortgage-backed securities
Issued or guaranteed by FNMA, FHLMC or GNMA		238,668		(2,902	)		11,090		(154	)		249,758		(3,056	)
Asset-backed securities and structured financial products		6,778		(125	)		—		—			6,778		(125	)
Total	$	1,506,669	$	(12,487	)	$	284,538	$	(7,772	)	$	1,791,207	$	(20,259	)

December 31, 2014
U.S. Government agency obligations
Issued by U.S. Government agencies	$	19,220	$	(115	)	$	32,656	$	(711	)	$	51,876	$	(826	)
Issued by U.S. Government sponsored agencies		9,948		(52	)		9,956		(25	)		19,904		(77	)
Obligations of states and political subdivisions		8,431		(22	)		3,800		(46	)		12,231		(68	)
Mortgage-backed securities
Residential mortgage pass-through securities
Guaranteed by GNMA		7,199		(22	)		647		(8	)		7,846		(30	)
Other residential mortgage-backed securities
Issued or guaranteed by FNMA, FHLMC or GNMA		537,033		(2,449	)		395,342		(10,031	)		932,375		(12,480	)
Commercial mortgage-backed securities
Issued or guaranteed by FNMA, FHLMC or GNMA		9,134		(3	)		79,829		(1,088	)		88,963		(1,091	)
Total	$	590,965	$	(2,663	)	$	522,230	$	(11,909	)	$	1,113,195	$	(14,572	)

Gains and Losses as a Result of Calls and Disposition of Securities

For the periods presented, gains and losses as a result of calls and dispositions of securities, as well as any associated proceeds, were as follows ($ in thousands):

	Years Ended December 31,
Available for Sale	2015		2014			2013
Proceeds from calls and sales of securities	$	—	$	56,815		$	224,853
Gross realized gains		—		456			1,680
Gross realized losses		—		(156	)		(1,195	)

Contractual Maturities of Available for Sale and Held to Maturity Securities

The amortized cost and estimated fair value of securities available for sale and held to maturity at December 31, 2015, by contractual maturity, are shown below ($ in thousands). Expected maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties.

	Securities				Securities
	Available for Sale				Held to Maturity
			Estimated				Estimated
	Amortized		Fair		Amortized		Fair
	Cost		Value		Cost		Value
Due in one year or less	$	20,805	$	20,982	$	6,300	$	6,505
Due after one year through five years		113,325		117,050		60,315		61,936
Due after five years through ten years		16,997		17,562		91,059		95,433
Due after ten years		77,167		76,388		—		—
		228,294		231,982		157,674		163,874
Mortgage-backed securities		2,111,268		2,113,440		1,030,144		1,031,493
Total	$	2,339,562	$	2,345,422	$	1,187,818	$	1,195,367

- Definition

Tabular disclosure of the realized and unrealized gains and losses reported in the statement of income which have resulted from the sale and holding of marketable securities, respectively, as well as the sale or disposal of cost method investments. Such amounts would include realized gains and losses on the sale or disposal of trading, available-for-sale, and held-to-maturity securities, unrealized gains and losses on trading securities, unrealized gains and losses on available-for-sale and held-to-maturity securities transferred to the trading securities category, realized gains and losses on the sale or disposal of cost method investments, and losses recognized for other than temporary impairments (OTTI) of such investments.

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