Investment Securities Held-to-Maturity (Tables)

12 Months Ended

Dec. 31, 2015

Text Block [Abstract]

Summary of Held-to-Maturity Securities

	December 31, 2015								December 31, 2014
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
(dollars in thousands)
U.S. Government Sponsored Enterprises	$	186,734	$	2,234	$	141	$	188,827	$	251,617	$	2,707	$	249	$	254,075
U.S. Government Sponsored Enterprises Mortgage-Backed Securities		1,252,169		7,547		9,583		1,250,133		1,155,175		11,185		6,832		1,159,528
Total	$	1,438,903	$	9,781	$	9,724	$	1,438,960	$	1,406,792	$	13,892	$	7,081	$	1,413,603

Company's Securities Held-to-Maturity

The following table shows the maturity distribution of the Company’s securities held-to-maturity at December 31, 2015.

	Amortized Cost		Fair Value
(dollars in thousands)
Within one year	$	1,712	$	1,728
After one but within five years		1,144,391		1,143,393
After five but within ten years		289,646		290,692
More than ten years		3,154		3,147
Total	$	1,438,903	$	1,438,960

Unrealized Market Loss of Securities

The following table shows the temporarily impaired securities of the Company’s held-to-maturity portfolio at December 31, 2015. This table shows the unrealized market loss of securities that have been in a continuous unrealized loss position for 12 months or less and a continuous loss position for 12 months and longer. There are 101 and 26 securities that are temporarily impaired for less than 12 months and for 12 months or longer, respectively, out of a total of 322 holdings at December 31, 2015.

	December 31, 2015
	Less Than 12 Months				12 Months or Longer				Total
Temporarily Impaired Investments	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
(dollars in thousands)
U.S. Government Sponsored Enterprises	$	9,859	$	141	$	—	$	—	$	9,859	$	141
U.S. Government Agency and Sponsored
Enterprise Mortgage-Backed Securities		626,218		6,657		123,864		2,926		750,082		9,583
Total temporarily impaired securities	$	636,077	$	6,798	$	123,864	$	2,926	$	759,941	$	9,724

The following table shows the temporarily impaired securities of the Company’s held-to-maturity portfolio at December 31, 2014. This table shows the unrealized market loss of securities that have been in a continuous unrealized loss position for 12 months or less and a continuous loss position for 12 months and longer. There are 34 and 48 securities that are temporarily impaired for less than 12 months and for 12 months or longer, respectively, out of a total of 303 holdings at December 31, 2014.

	December 31, 2014
	Less Than 12 Months				12 Months or Longer				Total
Temporarily Impaired Investments	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
(dollars in thousands)
U.S. Government Sponsored Enterprises	$	22,414	$	25	$	14,776	$	224	$	37,190	$	249
U.S. Government Agency and Sponsored
Enterprise Mortgage-Backed Securities		194,119		1,678		308,526		5,154		502,645		6,832
Total temporarily impaired securities	$	216,533	$	1,703	$	323,302	$	5,378	$	539,835	$	7,081