Investments (Tables)

12 Months Ended

Dec. 31, 2015

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 December 31, 2015 and 2014, were as follows:

	December 31, 2015
(Dollars in thousands)	Cost		Gross unrealized gains		Gross unrealized losses		Fair value
Investment securities available for sale
U.S. Treasury	$	1,675,996	$	4	$	1,118	$	1,674,882
Government agency	498,804		230		374		498,660
Mortgage-backed securities	4,692,447		5,120		29,369		4,668,198
Equity securities	7,935		968		10		8,893
Other	10,615		45		—		10,660
Total investment securities available for sale	$	6,885,797	$	6,367	$	30,871	$	6,861,293
	December 31, 2014
	Cost		Gross unrealized gains		Gross unrealized losses		Fair value
U.S. Treasury	$	2,626,900	$	2,922	$	152	$	2,629,670
Government agency	908,362		702		247		908,817
Mortgage-backed securities	3,628,187		16,964		11,847		3,633,304
Municipal securities	125		1		—		126
Total investment securities available for sale	$	7,163,574	$	20,589	$	12,246	$	7,171,917
	December 31, 2015
	Cost		Gross unrealized gains		Gross unrealized losses		Fair value
Investment securities held to maturity
Mortgage-backed securities	$	255	$	10	$	—	$	265
	December 31, 2014
	Cost		Gross unrealized gains		Gross unrealized losses		Fair value
Mortgage-backed securities	$	518	$	26	$	—	$	544

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.

	December 31, 2015				December 31, 2014
(Dollars in thousands)	Cost		Fair value		Cost		Fair value
Investment securities available for sale
Non-amortizing securities maturing in:
One year or less	$	1,255,714	$	1,255,094	$	447,866	$	447,992
One through five years	919,086		918,448		3,087,521		3,090,621
Five through 10 years	8,500		8,500		—		—
Over 10 years	2,115		2,160		—		—
Mortgage-backed securities	4,692,447		4,668,198		3,628,187		3,633,304
Equity securities	7,935		8,893		—		—
Total investment securities available for sale	$	6,885,797	$	6,861,293	$	7,163,574	$	7,171,917
Investment securities held to maturity
Mortgage-backed securities held to maturity	$	255	$	265	$	518	$	544

Securities Gains (Losses)

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

	Year ended December 31
(Dollars in thousands)	2015			2014			2013
Gross gains on retirement/sales of investment securities available for sale	$	10,834		$	29,129		$	—
Gross losses on sales of investment securities available for sale	(17		)	(33		)	—
Total securities gains	$	10,817		$	29,096		$	—

Investment Securities With Unrealized Losses

The following table provides information regarding securities with unrealized losses as of December 31, 2015 and 2014:

	December 31, 2015
	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	$	1,539,637	$	1,118	$	—	$	—	$	1,539,637	$	1,118
Government agency	229,436		374		—		—		229,436		374
Mortgage-backed securities	3,570,470		23,275		280,126		6,094		3,850,596		29,369
Equity securities	728		10		—		—		728		10
Other	—		—		—		—		—		—
Total	$	5,340,271	$	24,777	$	280,126	$	6,094	$	5,620,397	$	30,871
	December 31, 2014
	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	$	338,612	$	151	$	1,015	$	1	$	339,627	$	152
Government agency	261,288		247		—		—		261,288		247
Mortgage-backed securities	573,374		1,805		831,405		10,042		1,404,779		11,847
Total	$	1,173,274	$	2,203	$	832,420	$	10,043	$	2,005,694	$	12,246