Investment Securities (Tables)

3 Months Ended

Mar. 31, 2016

Investments, Debt and Equity Securities [Abstract]

Schedule of Amortized Cost and Fair Values of Investment Securities

The following table presents the amortized cost and estimated fair values of investment securities, which were all classified as available for sale:

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in thousands)
March 31, 2016
U.S. Government sponsored agency securities	$	25,149	$	24	$	—		$	25,173
State and municipal securities	307,038		7,025		(53		)	314,010
Corporate debt securities	95,389		2,773		(8,276		)	89,886
Collateralized mortgage obligations	782,018		5,322		(5,265		)	782,075
Mortgage-backed securities	1,169,552		19,454		(338		)	1,188,668
Auction rate securities	106,871		—		(9,545		)	97,326
Total debt securities	2,486,017		34,598		(23,477		)	2,497,138
Equity securities	14,228		4,852		(13		)	19,067
Total	$	2,500,245	$	39,450	$	(23,490	)	$	2,516,205

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in thousands)
December 31, 2015
U.S. Government sponsored agency securities	$	25,154	$	35	$	(53	)	$	25,136
State and municipal securities	256,746		6,019		—			262,765
Corporate debt securities	100,336		2,695		(6,076		)	96,955
Collateralized mortgage obligations	835,439		3,042		(16,972		)	821,509
Mortgage-backed securities	1,154,935		10,104		(6,204		)	1,158,835
Auction rate securities	106,772		—		(8,713		)	98,059
Total debt securities	2,479,382		21,895		(38,018		)	2,463,259
Equity securities	$	14,677	$	6,845	$	(8	)	$	21,514
Total	2,494,059		28,740		(38,026		)	2,484,773

Schedule of Amortized Cost and Fair Values of Debt Securities by Contractual Maturities

The amortized cost and estimated fair values of debt securities as of March 31, 2016, by contractual maturity, are shown in the following table. Actual maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties.

		Amortized Cost		Estimated Fair Value
	(in thousands)
Due in one year or less		$	64,096	$	64,475
Due from one year to five years		89,237		91,302
Due from five years to ten years		92,154		95,021
Due after ten years		288,960		275,597
		534,447		526,395
Collateralized mortgage obligations		782,018		782,075
Mortgage-backed securities		1,169,552		1,188,668
Total debt securities		$	2,486,017	$	2,497,138

Summary of Gains and Losses from Equity and Debt Securities, and Losses Recognized from Other-than-Temporary Impairment

The following table presents information related to the gross realized gains on the sales of equity and debt securities:

	Gross Realized Gains		Gross Realized Losses		Net Gains (Losses)
Three months ended March 31, 2016	(in thousands)
Equity securities	$	733	$	—	$	733
Debt securities	214		—		214
Total	$	947	$	—	$	947
Three months ended March 31, 2015
Equity securities	$	1,970	$	—	$	1,970
Debt securities	2,175		—		2,175
Total	$	4,145	$	—	$	4,145

Summary Of Other Than Temporary Impairment Charges Recorded In Statement Of Operations [Table Text Block]

The following table presents a summary of the cumulative credit related other-than-temporary impairment charges, recognized as components of earnings, for debt securities held by the Corporation at March 31, 2016 and 2015:

	Three months ended March 31
	2016			2015
	(in thousands)
Balance of cumulative credit losses on debt securities, beginning of period	$	(11,510	)	$	(16,242	)
Reductions for securities sold during the period	—			3,938
Reductions for increases in cash flows expected to be collected that are recognized over the remaining life of the security	—			2
Balance of cumulative credit losses on debt securities, end of period	$	(11,510	)	$	(12,302	)

Gross Unrealized Losses and Fair Values of Investments by Category and Length of Time in Continuous Unrealized Loss Position

The following table presents the gross unrealized losses and estimated fair values of investments, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position at March 31, 2016:

	Less than 12 months					12 months or longer					Total
	Estimated Fair Value		Unrealized Losses			Estimated Fair Value		Unrealized Losses			Estimated Fair Value		Unrealized Losses
	(in thousands)
State and municipal securities	$	17,961	$	(53	)	$	—	$	—		$	17,961	$	(53	)
Corporate debt securities	—		—			30,762		(8,276		)	30,762		(8,276		)
Collateralized mortgage obligations	21,078		(87		)	461,807		(5,178		)	482,885		(5,265		)
Mortgage-backed securities	98,180		(175		)	30,243		(163		)	128,423		(338		)
Auction rate securities	—		—			97,326		(9,545		)	97,326		(9,545		)
Total debt securities	137,219		(315		)	620,138		(23,162		)	757,357		(23,477		)
Equity securities	50		(3		)	12		(10		)	62		(13		)
	$	137,269	$	(318	)	$	620,150	$	(23,172	)	$	757,419	$	(23,490	)

Summary of Amortized Cost and Fair Values of Corporate Debt Securities

The following table presents the amortized cost and estimated fair value of corporate debt securities:

	March 31, 2016				December 31, 2015
	Amortized cost		Estimated fair value		Amortized cost		Estimated fair value
	(in thousands)
Single-issuer trust preferred securities	$	43,673	$	35,851	$	44,648	$	39,106
Subordinated debt	47,681		49,294		51,653		53,108
Pooled trust preferred securities	—		706		—		706
Corporate debt securities issued by financial institutions	91,354		85,851		96,301		92,920
Other corporate debt securities	4,035		4,035		4,035		4,035
Available for sale corporate debt securities	$	95,389	$	89,886	$	100,336	$	96,955