Investments (Tables)

3 Months Ended

Mar. 31, 2017

Investments [Abstract]

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, 2017 and December 31, 2016, are as follows:

	March 31, 2017
(Dollars in thousands)	Cost		Gross unrealized gains		Gross unrealized losses		Fair value
Investment securities available for sale
U.S. Treasury	$	1,619,380	$	342	$	1,554	$	1,618,168
Government agency	40,185		36		—		40,221
Mortgage-backed securities	5,363,747		2,946		60,586		5,306,107
Equity securities	72,064		22,201		—		94,265
Corporate bonds	49,370		220		25		49,565
Other	11,702		45		212		11,535
Total investment securities available for sale	$	7,156,448	$	25,790	$	62,377	$	7,119,861
	December 31, 2016
	Cost		Gross unrealized gains		Gross unrealized losses		Fair value
U.S. Treasury	$	1,650,675	$	579	$	935	$	1,650,319
Government agency	40,291		107		—		40,398
Mortgage-backed securities	5,259,466		2,809		86,850		5,175,425
Equity securities	71,873		11,634		—		83,507
Corporate bonds	49,367		195		—		49,562
Other	7,615		—		246		7,369
Total investment securities available for sale	$	7,079,287	$	15,324	$	88,031	$	7,006,580
	March 31, 2017
	Cost		Gross unrealized gains		Gross unrealized losses		Fair value
Investment securities held to maturity
Mortgage-backed securities	$	83	$	6	$	—	$	89
	December 31, 2016
	Cost		Gross unrealized gains		Gross unrealized losses		Fair value
Mortgage-backed securities	$	98	$	6	$	—	$	104

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. Equity securities do not have a stated maturity date.

	March 31, 2017				December 31, 2016
(Dollars in thousands)	Cost		Fair value		Cost		Fair value
Investment securities available for sale
Non-amortizing securities maturing in:
One year or less	$	550,275	$	549,566	$	842,798	$	842,947
One through five years	1,109,290		1,108,823		848,168		847,770
Five through 10 years	49,370		49,565		49,367		49,562
Over 10 years	11,702		11,535		7,615		7,369
Mortgage-backed securities	5,363,747		5,306,107		5,259,466		5,175,425
Equity securities	72,064		94,265		71,873		83,507
Total investment securities available for sale	$	7,156,448	$	7,119,861	$	7,079,287	$	7,006,580
Investment securities held to maturity
Mortgage-backed securities held to maturity	$	83	$	89	$	98	$	104

Securities Gains (Losses)

For each period presented, realized securities gains (losses) included the following:

	Three months ended March 31
(Dollars in thousands)	2017			2016
Gross gains on sales of investment securities available for sale	$	3		$	4,933
Gross losses on sales of investment securities available for sale	(27		)	(305		)
Total realized securities (losses) gains	$	(24	)	$	4,628

Investment Securities With Unrealized Losses

The following table provides information regarding securities with unrealized losses as of March 31, 2017 and December 31, 2016.

	March 31, 2017
	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	$	1,068,144	$	1,554	$	—	$	—	$	1,068,144	$	1,554
Mortgage-backed securities	4,318,258		56,017		361,488		4,569		4,679,746		60,586
Corporate bonds	9,975		25		—		—		9,975		25
Other	5,294		212		—		—		5,294		212
Total	$	5,401,671	$	57,808	$	361,488	$	4,569	$	5,763,159	$	62,377
	December 31, 2016
	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	$	807,822	$	935	$	—	$	—	$	807,822	$	935
Mortgage-backed securities	4,442,700		82,161		362,351		4,689		4,805,051		86,850
Other	7,369		246		—		—		7,369		246
Total	$	5,257,891	$	83,342	$	362,351	$	4,689	$	5,620,242	$	88,031