Investments (Tables)

3 Months Ended

Mar. 31, 2018

Gain (Loss) on Investments [Line Items]

Aggregate Values And Unrealized Gains And Losses Of Investment Securities

The amortized cost and fair value of investment securities classified as available for sale and held to maturity at March 31, 2018 and December 31, 2017, are as follows:

	March 31, 2018
(Dollars in thousands)	Cost		Gross unrealized gains		Gross unrealized losses		Fair value
Investment securities available for sale
U.S. Treasury	$	1,557,991	$	—	$	4,098	$	1,553,893
Government agency	32,006		12		109		31,909
Mortgage-backed securities	5,360,251		1,001		154,585		5,206,667
Corporate bonds	59,414		319		80		59,653
Other	5,538		80		—		5,618
Total investment securities available for sale	$	7,015,200	$	1,412	$	158,872	$	6,857,740
	December 31, 2017
	Cost		Gross unrealized gains		Gross unrealized losses		Fair value
Investment securities available for sale
U.S. Treasury	$	1,658,410	$	—	$	546	$	1,657,864
Government agency	8,695		15		40		8,670
Mortgage-backed securities	5,419,379		1,529		80,152		5,340,756
Equity securities	75,471		29,737		—		105,208
Corporate bonds	59,414		557		8		59,963
Other	7,645		256		182		7,719
Total investment securities available for sale	$	7,229,014	$	32,094	$	80,928	$	7,180,180
	March 31, 2018
	Cost		Gross unrealized gains		Gross unrealized losses		Fair value
Investment securities held to maturity
Mortgage-backed securities	$	74	$	5	$	—	$	79
	December 31, 2017
	Cost		Gross unrealized gains		Gross unrealized losses		Fair value
Investment securities held to maturity
Mortgage-backed securities	$	76	$	5	$	—	$	81

Investment Securities Maturity Information

The following table provides the amortized cost and fair value by contractual maturity. Expected maturities will differ from contractual maturities on certain securities because borrowers and issuers may have the right to call or prepay obligations with or without prepayment penalties. Repayments of mortgage-backed securities are dependent on the repayments of the underlying loan balances.

	March 31, 2018				December 31, 2017
(Dollars in thousands)	Cost		Fair value		Cost		Fair value
Investment securities available for sale
Non-amortizing securities maturing in:
One year or less	$	1,105,460	$	1,103,291	$	808,768	$	808,301
One through five years	453,082		451,152		850,532		850,450
Five through 10 years	60,303		60,546		60,332		60,886
Over 10 years	36,104		36,084		14,532		14,579
Mortgage-backed securities	5,360,251		5,206,667		5,419,379		5,340,756
Equity securities	—		—		75,471		105,208
Total investment securities available for sale	$	7,015,200	$	6,857,740	$	7,229,014	$	7,180,180
Investment securities held to maturity
Mortgage-backed securities held to maturity	$	74	$	79	$	76	$	81

Securities Gains (Losses)

Marketable Securities Gains (Losses)

The following table provides the realized and unrealized gains or losses on marketable equity securities for the three months ended March 31, 2018.

(Dollars in thousands)	Three months ended March 31, 2018
Marketable equity securities gains, net	$	971
Less net gains recognized on marketable equity securities sold	96
Unrealized gains recognized on marketable equity securities held	$	875

Investment Securities With Unrealized Losses

The following table provides information regarding securities available for sale with unrealized losses as of March 31, 2018 and December 31, 2017.

	March 31, 2018
	Less than 12 months				12 months or more				Total
(Dollars in thousands)	Fair value		Unrealized losses		Fair value		Unrealized losses		Fair value		Unrealized losses
Investment securities available for sale:
U.S. Treasury	$	1,453,968	$	4,049	$	99,925	$	49	$	1,553,893	$	4,098
Government agency	12,059		81		2,159		28		14,218		109
Mortgage-backed securities	2,404,338		58,606		2,535,662		95,979		4,940,000		154,585
Corporate bonds	9,950		80		—		—		9,950		80
Total	$	3,880,315	$	62,816	$	2,637,746	$	96,056	$	6,518,061	$	158,872
	December 31, 2017
	Less than 12 months				12 months or more				Total
	Fair value		Unrealized losses		Fair value		Unrealized losses		Fair value		Unrealized losses
Investment securities available for sale:
U.S. Treasury	$	1,408,166	$	345	$	249,698	$	201	$	1,657,864	$	546
Government agency	848		12		2,527		28		3,375		40
Mortgage-backed securities	2,333,254		20,911		2,723,406		59,241		5,056,660		80,152
Corporate bonds	5,025		8		—		—		5,025		8
Other	5,349		182		—		—		5,349		182
Total	$	3,752,642	$	21,458	$	2,975,631	$	59,470	$	6,728,273	$	80,928

Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block]

INVESTMENTS

The amortized cost and fair value of investment securities classified as available for sale and held to maturity at March 31, 2018 and December 31, 2017, are as follows:

	March 31, 2018
(Dollars in thousands)	Cost		Gross unrealized gains		Gross unrealized losses		Fair value
Investment securities available for sale
U.S. Treasury	$	1,557,991	$	—	$	4,098	$	1,553,893
Government agency	32,006		12		109		31,909
Mortgage-backed securities	5,360,251		1,001		154,585		5,206,667
Corporate bonds	59,414		319		80		59,653
Other	5,538		80		—		5,618
Total investment securities available for sale	$	7,015,200	$	1,412	$	158,872	$	6,857,740
	December 31, 2017
	Cost		Gross unrealized gains		Gross unrealized losses		Fair value
Investment securities available for sale
U.S. Treasury	$	1,658,410	$	—	$	546	$	1,657,864
Government agency	8,695		15		40		8,670
Mortgage-backed securities	5,419,379		1,529		80,152		5,340,756
Equity securities	75,471		29,737		—		105,208
Corporate bonds	59,414		557		8		59,963
Other	7,645		256		182		7,719
Total investment securities available for sale	$	7,229,014	$	32,094	$	80,928	$	7,180,180
	March 31, 2018
	Cost		Gross unrealized gains		Gross unrealized losses		Fair value
Investment securities held to maturity
Mortgage-backed securities	$	74	$	5	$	—	$	79
	December 31, 2017
	Cost		Gross unrealized gains		Gross unrealized losses		Fair value
Investment securities held to maturity
Mortgage-backed securities	$	76	$	5	$	—	$	81

As a result of adopting ASU 2016-01 in the first quarter of 2018, investments in marketable equity securities are no longer classified as investments available for sale. At March 31, 2018 and December 31, 2017, we had $110.1 million and $105.2 million, respectively, in marketable equity securities recorded at fair value. Prior to January 1, 2018 equity securities were classified as available for sale and stated at fair value with unrealized gains and losses reported in accumulated other comprehensive income. A cumulative-effect adjustment of $18.7 million was recorded on January 1, 2018 to reclassify the net unrealized gains from accumulated other comprehensive income to retained earnings with subsequent changes in fair value recognized in the Consolidated Statements of Income.

Investments in mortgage-backed securities primarily represent securities issued by the Government National Mortgage Association, Federal National Mortgage Association and Federal Home Loan Mortgage Corporation. Investments in corporate bonds and marketable equity securities represent positions in securities of other financial institutions. Other investments include trust preferred securities of financial institutions. The following table provides the amortized cost and fair value by contractual maturity. Expected maturities will differ from contractual maturities on certain securities because borrowers and issuers may have the right to call or prepay obligations with or without prepayment penalties. Repayments of mortgage-backed securities are dependent on the repayments of the underlying loan balances.

	March 31, 2018				December 31, 2017
(Dollars in thousands)	Cost		Fair value		Cost		Fair value
Investment securities available for sale
Non-amortizing securities maturing in:
One year or less	$	1,105,460	$	1,103,291	$	808,768	$	808,301
One through five years	453,082		451,152		850,532		850,450
Five through 10 years	60,303		60,546		60,332		60,886
Over 10 years	36,104		36,084		14,532		14,579
Mortgage-backed securities	5,360,251		5,206,667		5,419,379		5,340,756
Equity securities	—		—		75,471		105,208
Total investment securities available for sale	$	7,015,200	$	6,857,740	$	7,229,014	$	7,180,180
Investment securities held to maturity
Mortgage-backed securities held to maturity	$	74	$	79	$	76	$	81

There were no sales of investment securities available for sale for the three months ended March 31, 2018. Gross gains and gross losses on sales of investment securities available for sale were $3 thousand and $27 thousand, respectively for the three months ended March 31, 2017.

The following table provides the realized and unrealized gains or losses on marketable equity securities for the three months ended March 31, 2018.

(Dollars in thousands)	Three months ended March 31, 2018
Marketable equity securities gains, net	$	971
Less net gains recognized on marketable equity securities sold	96
Unrealized gains recognized on marketable equity securities held	$	875

The following table provides information regarding securities available for sale with unrealized losses as of March 31, 2018 and December 31, 2017.

	March 31, 2018
	Less than 12 months				12 months or more				Total
(Dollars in thousands)	Fair value		Unrealized losses		Fair value		Unrealized losses		Fair value		Unrealized losses
Investment securities available for sale:
U.S. Treasury	$	1,453,968	$	4,049	$	99,925	$	49	$	1,553,893	$	4,098
Government agency	12,059		81		2,159		28		14,218		109
Mortgage-backed securities	2,404,338		58,606		2,535,662		95,979		4,940,000		154,585
Corporate bonds	9,950		80		—		—		9,950		80
Total	$	3,880,315	$	62,816	$	2,637,746	$	96,056	$	6,518,061	$	158,872
	December 31, 2017
	Less than 12 months				12 months or more				Total
	Fair value		Unrealized losses		Fair value		Unrealized losses		Fair value		Unrealized losses
Investment securities available for sale:
U.S. Treasury	$	1,408,166	$	345	$	249,698	$	201	$	1,657,864	$	546
Government agency	848		12		2,527		28		3,375		40
Mortgage-backed securities	2,333,254		20,911		2,723,406		59,241		5,056,660		80,152
Corporate bonds	5,025		8		—		—		5,025		8
Other	5,349		182		—		—		5,349		182
Total	$	3,752,642	$	21,458	$	2,975,631	$	59,470	$	6,728,273	$	80,928

Investment securities available for sale with an aggregate fair value of $2.64 billion and $2.98 billion had continuous unrealized losses for more than 12 months with a corresponding aggregate unrealized loss of $96.1 million and $59.5 million as of March 31, 2018 and December 31, 2017, respectively. As of March 31, 2018, 224 of these are government sponsored enterprise-issued mortgage-backed securities or government agency securities and 1 is a U.S. Treasury security.

None of the unrealized losses identified as of March 31, 2018 or December 31, 2017 relate to the marketability of the securities or the issuers' ability to honor redemption obligations. Rather, the unrealized losses relate to changes in interest rates relative to when the debt securities were purchased. For all periods presented, BancShares had the ability and intent to retain these securities for a period of time sufficient to recover all unrealized losses. Therefore, none of the securities were deemed to be other than temporarily impaired.

Debt securities having an aggregate carrying value of $3.83 billion at March 31, 2018 and $4.59 billion at December 31, 2017 were pledged as collateral to secure public funds on deposit and certain short-term borrowings, and for other purposes as required by law.

On May 1, 2018, mortgage-backed securities with an amortized cost of $2.49 billion were transferred from investments available for sale to the held to maturity portfolio. At the time of transfer, the mortgage-backed securities had a fair value of $2.38 billion and a weighted average maturity of 13 years. FCB has the intent and ability to retain these securities until maturity.