Investment Securities (Tables)

12 Months Ended

Dec. 31, 2014

Amortized cost and estimated fair value by type of investment security

The amortized cost and estimated fair value by type of investment security at December 31, 2014 are as follows:

	Held to Maturity
	Amortized cost		Gross unrealized gains		Gross unrealized losses		Estimated fair value		Carrying value
	(Dollars in Thousands)
Other securities	$	2,400	$	—	$	—	$	2,400	$	2,400

Total investment securities	$	2,400	$	—	$	—	$	2,400	$	2,400

	Available for Sale
	Amortized cost		Gross unrealized gains		Gross unrealized losses			Estimated fair value		Carrying value(1)
	(Dollars in Thousands)
Residential mortgage-backed securities	$	4,597,590	$	47,960	$	(45,178	)	$	4,600,372	$	4,600,372
Obligations of states and political subdivisions		268,763		19,131		(5,618	)		282,276		282,276
Other debt securities		20,000		—		—			20,000		20,000
Equity securities		28,075		1,425		(185	)		29,315		29,315

Total investment securities	$	4,914,428	$	68,516	$	(50,981	)	$	4,931,963	$	4,931,963

(1)	Included in the carrying value of residential mortgage-backed securities are $1,503,774 of mortgage-backed securities issued by Ginnie Mae, $3,072,535 of mortgage-backed securities issued by Fannie Mae and Freddie Mac and $24,063 issued by non-government entities

The amortized cost and estimated fair value by type of investment security at December 31, 2013 are as follows:

	Held to Maturity
	Amortized cost		Gross unrealized gains		Gross unrealized losses		Estimated fair value		Carrying value
	(Dollars in Thousands)
Other securities	$	2,400	$	—	$	—	$	2,400	$	2,400

Total investment securities	$	2,400	$	—	$	—	$	2,400	$	2,400

	Available for Sale
	Amortized cost		Gross unrealized gains		Gross unrealized losses			Estimated fair value		Carrying value(1)
	(Dollars in Thousands)
Residential mortgage-backed securities	$	5,096,165	$	56,110	$	(124,574	)	$	5,027,701	$	5,027,701
Obligations of states and political subdivisions		248,354		8,063		(8,007	)		248,410		248,410
Equity securities		28,075		931		(538	)		28,468		28,468

Total investment securities	$	5,372,594	$	65,104	$	(133,119	)	$	5,304,579	$	5,304,579

(1)	Included in the carrying value of residential mortgage-backed securities are $1,799,807 of mortgage-backed securities issued by Ginnie Mae, $3,200,042 of mortgage-backed securities issued by Fannie Mae and Freddie Mac and $27,852 issued by non-government entities

Amortized cost and fair value of investment securities, by contractual maturity

The amortized cost and estimated fair value of investment securities at December 31, 2014, by contractual maturity, are shown below.

	Held to Maturity				Available for Sale
	Amortized Cost		Estimated fair value		Amortized Cost		Estimated fair value
	(Dollars in Thousands)
Due in one year or less	$	1,075	$	1,075	$	—	$	—
Due after one year through five years		1,325		1,325		—		—
Due after five years through ten years		—		—		735		812
Due after ten years		—		—		288,028		301,464
Residential mortgage-backed securities		—		—		4,597,590		4,600,372
Equity securities		—		—		28,075		29,315

Total investment securities	$	2,400	$	2,400	$	4,914,428	$	4,931,963

Gross unrealized losses on investment securities and the related fair value

Gross unrealized losses on investment securities and the fair value of the related securities, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position, at December 31, 2014 were as follows:

	Less than 12 months					12 months or more					Total
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
	(Dollars in Thousands)
Available for sale:
Residential mortgage-backed securities	$	808,072	$	(4,910	)	$	1,836,218	$	(40,268	)	$	2,644,290	$	(45,178	)
Obligations of states and political subdivisions		8,833		(97	)		27,793		(5,521	)		36,626		(5,618	)
Equity securities		74		(1	)		8,066		(184	)		8,140		(185	)

	$	816,979	$	(5,008	)	$	1,872,077	$	(45,973	)	$	2,689,056	$	(50,981	)

Gross unrealized losses on investment securities and the fair value of the related securities, aggregated by investment category and length of time that individual securities have been in a continuous loss position, at December 31, 2013 were as follows:

	Less than 12 months					12 months or more					Total
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
	(Dollars in Thousands)
Available for sale:
Residential mortgage-backed securities	$	2,459,565	$	(98,022	)	$	420,262	$	(26,552	)	$	2,879,827	$	(124,574	)
Obligations of states and political subdivisions		55,327		(3,025	)		14,292		(4,982	)		69,619		(8,007	)
Equity securities		19,462		(538	)		—		—			19,462		(538	)

	$	2,534,354	$	(101,585	)	$	434,554	$	(31,534	)	$	2,968,908	$	(133,119	)

Reconciliation of credit-related impairment charges on available-for-sale investment

The following table presents a reconciliation of credit-related impairment charges on available-for-sale investments recognized in earnings for the twelve months ended December 31, 2014 (in Thousands):

Balance at December 31, 2013	$	11,806
Impairment charges recognized during period		817

Balance at December 31, 2014	$	12,623

Balance at December 31, 2012	$	10,432
Impairment charges recognized during period		1,374

Balance at December 31, 2013	$	11,806

Balance at December 31, 2011	$	9,393
Impairment charges recognized during period		1,039

Balance at December 31, 2012	$	10,432

- Definition

Tabular disclosure of the amount of other than temporary impairment (OTTI) related to credit losses recognized in earnings including: (a) the beginning balance of the amount related to credit losses on debt securities held by the investor at the beginning of the period for which a portion of an OTTI was recognized in other comprehensive income; (b) additions for the amount related to the credit loss for which an OTTI was not previously recognized; (c) reductions for securities sold during the period (realized); (d) reductions for securities for which the amount previously recognized in other comprehensive income was recognized in earnings because the investor intends to sell the security or more likely than not will be required to sell the security before recovery of its amortized cost basis; (e) additional increases to the amount related to the credit loss for which an OTTI was previously recognized when the investor does not intend to sell the security and it is not more likely than not that the investor will be required to sell the security before recovery of its amortized cost basis; (f) reductions for increases in cash flows expected to be collected that are recognized over the remaining life of the security; and (g) the ending balance of the amount related to credit losses on debt securities held by the entity at the end of the period for which a portion of an OTTI was recognized in other comprehensive income.

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