Investment Securities Available for Sale (Tables)

12 Months Ended

Dec. 31, 2016

Summary of Available-for-Sale Investment Securities

The amortized cost, gross unrealized gains and losses, and estimated fair values of investment securities available for sale at December 31, 2016 and 2015 are summarized below.



	December 31, 2016
(in thousands)	Amortized Cost		Gross Unrealized Gains	Gross Unrealized Losses		Fair Value
U.S. Treasury securities	$	108,221	225	(644	)	107,802
U.S. Government agency securities	12,727		266	—		12,993
Mortgage-backed securities issued by U.S. Government agencies	174,440		1,116	(1,354	)	174,202
Mortgage-backed securities issued by U.S. Government sponsored enterprises	2,543,495		5,416	(42,571	)	2,506,340
Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises	905,789		1,214	(16,561	)	890,442
State and municipal securities	2,780		14	—		2,794
Equity securities	919		2,863	—		3,782
Other investments	20,247		—	(407	)	19,840
Total investment securities available for sale	$	3,768,618	11,114	(61,537	)	3,718,195

	December 31, 2015
(in thousands)	Amortized Cost		Gross Unrealized Gains	Gross Unrealized Losses		Fair Value
U.S. Treasury securities	$	43,125	232	—		43,357
U.S. Government agency securities	13,087		536	—		13,623
Securities issued by U.S. Government sponsored enterprises	126,520		389	—		126,909
Mortgage-backed securities issued by U.S. Government agencies	209,785		1,340	(1,121	)	210,004
Mortgage-backed securities issued by U.S. Government sponsored enterprises	2,645,107		7,874	(22,562	)	2,630,419
Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises	530,426		2,396	(3,225	)	529,597
State and municipal securities	4,343		92	(1	)	4,434
Equity securities	3,228		6,444	—		9,672
Other investments	20,177		—	(374	)	19,803
Total investment securities available for sale	$	3,595,798	19,303	(27,283	)	3,587,818

Schedule of Unrealized Loss on Investments

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, 2016 and December 31, 2015 are presented below.



	December 31, 2016
	Less than 12 Months			12 Months or Longer		Total
(in thousands)	Fair Value		Gross Unrealized Losses	Fair Value	Gross Unrealized Losses	Fair Value	Gross Unrealized Losses
U.S. Treasury securities	64,023		644	—	—	64,023	644
Mortgage-backed securities issued by U.S. Government agencies	128,121		1,240	3,626	114	131,747	1,354
Mortgage-backed securities issued by U.S. Government sponsored enterprises	2,123,181		42,571	—	—	2,123,181	42,571
Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises	682,492		15,653	24,801	908	707,293	16,561
Other investments	14,952		48	4,888	359	19,840	407
Total	$	3,012,769	60,156	33,315	1,381	3,046,084	61,537

	December 31, 2015
	Less than 12 Months			12 Months or Longer		Total
(in thousands)	Fair Value		Gross Unrealized Losses	Fair Value	Gross Unrealized Losses	Fair Value	Gross Unrealized Losses
Mortgage-backed securities issued by U.S. Government agencies	122,626		639	18,435	482	141,061	1,121
Mortgage-backed securities issued by U.S. Government sponsored enterprises	1,656,194		12,874	489,971	9,688	2,146,165	22,562
Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises	196,811		963	72,366	2,262	269,177	3,225
State and municipal securities	—		—	50	1	50	1
Other investments	14,985		15	4,818	359	19,803	374
Total	$	1,990,616	14,491	585,640	12,792	2,576,256	27,283

Amortized Cost and Estimated Fair Value by Contractual Maturity of Investment Securities Available-for-Sale

For purposes of the maturity table, mortgage-backed securities and CMOs, which are not due at a single maturity date, have been classified based on the final contractual maturity date.



	Distribution of Maturities at December 31, 2016
(in thousands)	Within One Year		1 to 5 Years	5 to 10 Years	More Than 10 Years	No Stated Maturity	Total
Amortized Cost
U.S. Treasury securities	$	18,435	89,786	—	—	—	108,221
U.S. Government agency securities	999		5,929	5,799	—	—	12,727
Mortgage-backed securities issued by U.S. Government agencies	—		—	14,345	160,095	—	174,440
Mortgage-backed securities issued by U.S. Government sponsored enterprises	154		86	624,561	1,918,694	—	2,543,495
Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises	—		—	—	905,789	—	905,789
State and municipal securities	110		240	—	2,430	—	2,780
Equity securities	—		—	—	—	919	919
Other investments	—		—	15,000	2,000	3,247	20,247
Total amortized cost	$	19,698	96,041	659,705	2,989,008	4,166	3,768,618
Fair Value
U.S. Treasury securities	$	18,435	89,367	—	—	—	107,802
U.S. Government agency securities	1,021		6,019	5,953	—	—	12,993
Mortgage-backed securities issued by U.S. Government agencies	—		—	14,784	159,418	—	174,202
Mortgage-backed securities issued by U.S. Government sponsored enterprises	158		88	624,216	1,881,878	—	2,506,340
Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises	—		—	—	890,442	—	890,442
State and municipal securities	110		240	—	2,444	—	2,794
Equity securities	—		—	—	—	3,782	3,782
Other investments	—		—	14,952	1,796	3,092	19,840
Total fair value	$	19,724	95,714	659,905	2,935,978	6,874	3,718,195

Summary of Sales Transactions in the Investment Securities Available-for-Sale Portfolio

OTTI charges of $88 thousand respectively, are included in gross realized losses for the year 2014. The specific identification method is used to reclassify gains and losses out of other comprehensive income at the time of sale.



(in thousands)	2016			2015			2014
Proceeds from sales of investment securities available for sale	$	968,606		347,954			20,815
Gross realized gains on sales ⁽¹⁾	$	9,586		$	4,356		$	1,419
Gross realized losses on sales	(3,575		)	(1,587		)	(88		)
Investment securities gains, net	$	6,011		2,769			1,331

⁽¹⁾ Includes $1.4 million in gains in 2016 from the transfer of $1.9 million of investment securities available for sale to trading account assets.