Investment Securities (Tables)

6 Months Ended

Jun. 30, 2017

Investments [Abstract]

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 June 30, 2017 and December 31, 2016 are summarized below.

	June 30, 2017
(in thousands)	Amortized Cost		Gross Unrealized Gains	Gross Unrealized Losses		Fair Value
U.S. Treasury securities	$	83,493	—	(360	)	83,133
U.S. Government agency securities	12,088		223	—		12,311
Mortgage-backed securities issued by U.S. Government agencies	132,710		640	(1,125	)	132,225
Mortgage-backed securities issued by U.S. Government sponsored enterprises	2,881,234		6,169	(30,998	)	2,856,405
Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises	734,804		84	(12,468	)	722,420
State and municipal securities	290		—	—		290
Corporate debt and other securities	20,279		205	(210	)	20,274
Total investment securities available for sale	$	3,864,898	7,321	(45,161	)	3,827,058
	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
Corporate debt and other securities	20,247		—	(407	)	19,840
Total investment securities available for sale	$	3,768,618	11,114	(61,537	)	3,718,195

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 June 30, 2017 and December 31, 2016 are presented below.

	June 30, 2017
	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	$	64,342	360	—	—	64,342	360
Mortgage-backed securities issued by U.S. Government agencies	95,492		1,125	—	—	95,492	1,125
Mortgage-backed securities issued by U.S. Government sponsored enterprises	2,161,449		30,998	—	—	2,161,449	30,998
Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises	668,342		11,678	23,212	790	691,554	12,468
Corporate debt and other securities	—		—	5,069	210	5,069	210
Total	$	2,989,625	44,161	28,281	1,000	3,017,906	45,161
	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
Corporate debt and other securities	14,952		48	4,888	359	19,840	407
Total	$	3,012,769	60,156	33,315	1,381	3,046,084	61,537

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 June 30, 2017
(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	$	18,791	64,702	—	—	—	83,493
U.S. Government agency securities	1,000		5,612	5,476	—	—	12,088
Mortgage-backed securities issued by U.S. Government agencies	—		—	34,868	97,842	—	132,710
Mortgage-backed securities issued by U.S. Government sponsored enterprises	47		2,262	535,035	2,343,890	—	2,881,234
Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises	—		—	22,173	712,631	—	734,804
State and municipal securities	110		180	—	—	—	290
Corporate debt and other securities	—		—	15,000	2,000	3,279	20,279
Total amortized cost	$	19,948	72,756	612,552	3,156,363	3,279	3,864,898
Fair Value
U.S. Treasury securities	$	18,791	64,342	—	—	—	83,133
U.S. Government agency securities	1,004		5,682	5,625	—	—	12,311
Mortgage-backed securities issued by U.S. Government agencies	—		—	35,007	97,218	—	132,225
Mortgage-backed securities issued by U.S. Government sponsored enterprises	48		2,390	529,968	2,323,999	—	2,856,405
Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises	—		—	21,950	700,470	—	722,420
State and municipal securities	110		180	—	—	—	290
Corporate debt and other securities	—		—	15,205	1,927	3,142	20,274
Total fair value	$	19,953	72,594	607,755	3,123,614	3,142	3,827,058

Schedule of Activity for Available-for-Sale Securities

Proceeds from sales, gross gains, and gross losses on sales of securities available for sale for the three months ended June 30, 2017 and 2016 are presented below. The specific identification method is used to reclassify gains and losses out of other comprehensive income at the time of sale.

	Six Months Ended June 30,					Three Months Ended June 30,
(in thousands)	2017			2016		2017			2016
Proceeds from sales of investment securities available for sale	$	338,381		243,609		$	55,752		—
Gross realized gains on sales	7,942			954		239			—
Gross realized losses on sales	(275		)	(887	)	(240		)	—
Investment securities gains, net	$	7,667		67		$	(1	)	—