Investment Securities (Tables)

6 Months Ended

Jun. 30, 2018

Investment Securities.

Schedule of amortized cost and fair values of investment securities

	Amortized		Gross Unrealized				Estimated
(Dollars in thousands)	Cost		Gains		Losses		Fair Value
June 30, 2018:
Available-for-sale:
U.S. government-sponsored mortgage-backed securities	$	2,764	$	—	$	(106)	$	2,658
Total	$	2,764	$	—	$	(106)	$	2,658
Held-to-maturity:
U.S. government-sponsored mortgage-backed securities	$	392,059	$	2,049	$	(11,877)	$	382,231
Trust preferred securities		130		601		—		731
Total	$	392,189	$	2,650	$	(11,877)	$	382,962
December 31, 2017:
Available-for-sale:
U.S. government-sponsored mortgage-backed securities	$	2,870	$	—	$	(19)	$	2,851
Total	$	2,870	$	—	$	(19)	$	2,851
Held-to-maturity:
U.S. government-sponsored mortgage-backed securities	$	404,365	$	6,056	$	(4,603)	$	405,818
Trust preferred securities		427		418		—		845
Total	$	404,792	$	6,474	$	(4,603)	$	406,663

Schedule of amortized cost and estimated fair value of investment securities by maturity

	Amortized		Estimated
(Dollars in thousands)	Cost		Fair Value
Available-for-sale:
Due within 5 years	$	—	$	—
Due after 5 years through 10 years		—		—
Due after 10 years		2,764		2,658
Total	$	2,764	$	2,658
Held-to-maturity:
Due within 5 years	$	7	$	7
Due after 5 years through 10 years		76		76
Due after 10 years		392,106		382,879
Total	$	392,189	$	382,962

Schedule of realized gains and losses and proceeds from sales of securities held to maturity

	Three Months Ended				Six Months Ended
	June 30,				June 30,
(Dollars in thousands)	2018		2017		2018		2017
Proceeds from sales	$	4,462	$	3,464	$	4,462	$	5,053
Gross gains		45		186		45		281
Gross losses		—		—		—		—

Summary of investment securities in an unrealized loss position

	Less Than 12 Months				12 Months or Longer				Total
			Unrealized				Unrealized		Number of			Unrealized
Description of securities	Fair Value		Losses		Fair Value		Losses		Securities	Fair Value		Losses
(Dollars in thousands)
June 30, 2018:
Available-for-sale:
U.S. government-sponsored mortgage-backed securities	$	2,658	$	106	$	—	$	—	1	$	2,658	$	106
Held-to-maturity:
U.S. government-sponsored mortgage-backed securities	$	170,316	$	3,782	$	128,277	$	8,095	88	$	298,593	$	11,877
December 31, 2017:
Available-for-sale:
U.S. government-sponsored mortgage-backed securities	$	2,851	$	19	$	—	$	—	1	$	2,851	$	19
Held-to-maturity:
U.S. government-sponsored mortgage-backed securities	$	41,163	$	299	$	140,200	$	4,304	49	$	181,363	$	4,603

Cumulative roll forward of credit losses recognized in earnings for debt securities held and not intended to be sold

	Six Months Ended June 30,
(Dollars in thousands)	2018		2017
Balance at the beginning of the period	$	2,403	$	2,403
Credit losses on debt securities for which other-than-temporary impairment was not previously recognized		—		—
Credit losses on debt securities which were sold		—		—
Balance at the end of the period	$	2,403	$	2,403