Investment Securities (Tables)

6 Months Ended

Jun. 30, 2015

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)
June 30, 2015
Equity securities	$	23,981	$	9,072	$	(12	)	$	33,041
U.S. Government sponsored agency securities	48,333		57		(130		)	48,260
State and municipal securities	231,592		5,312		(387		)	236,517
Corporate debt securities	98,756		3,183		(4,767		)	97,172
Collateralized mortgage obligations	931,093		4,932		(17,793		)	918,232
Mortgage-backed securities	998,418		14,112		(3,866		)	1,008,664
Auction rate securities	106,504		—		(7,898		)	98,606
	$	2,438,677	$	36,668	$	(34,853	)	$	2,440,492

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in thousands)
December 31, 2014
Equity securities	$	33,469	$	14,167	$	(13	)	$	47,623
U.S. Government securities	200		—		—			200
U.S. Government sponsored agency securities	209		5		—			214
State and municipal securities	238,250		7,231		(266		)	245,215
Corporate debt securities	99,016		5,126		(6,108		)	98,034
Collateralized mortgage obligations	917,395		5,705		(20,787		)	902,313
Mortgage-backed securities	914,797		16,978		(2,944		)	928,831
Auction rate securities	108,751		—		(7,810		)	100,941
	$	2,312,087	$	49,212	$	(37,928	)	$	2,323,371

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 June 30, 2015, 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		$	57,382	$	58,372
Due from one year to five years		104,022		106,663
Due from five years to ten years		148,682		151,430
Due after ten years		175,099		164,090
		485,185		480,555
Collateralized mortgage obligations		931,093		918,232
Mortgage-backed securities		998,418		1,008,664
		$	2,414,696	$	2,407,451

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 and losses on the sales of equity and debt securities:

	Gross Realized Gains		Gross Realized Losses			Other-than- temporary Impairment Losses			Net Gains (Losses)
Three months ended June 30, 2015	(in thousands)
Equity securities	$	2,290	$	—		$	—		$	2,290
Debt securities	125		—			—			125
Total	$	2,415	$	—		$	—		$	2,415
Three months ended June 30, 2014
Equity securities	$	—	$	—		$	(12	)	$	(12	)
Debt securities	1,124		—			—			1,124
Total	$	1,124	$	—		$	(12	)	$	1,112
Six months ended June 30, 2015
Equity securities	$	4,260	$	—		$	—		$	4,260
Debt securities	2,300		—			—			2,300
Total	$	6,560	$	—		$	—		$	6,560
Six months ended June 30, 2014
Equity securities	$	1	$	—		$	(12	)	$	(11	)
Debt securities	1,446		(323		)	—			1,123
Total	$	1,447	$	(323	)	$	(12	)	$	1,112

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 June 30, 2015 and 2014:

	Three months ended June 30						Six months ended June 30
	2015			2014			2015			2014
	(in thousands)
Balance of cumulative credit losses on debt securities, beginning of period	$	(12,302	)	$	(19,961	)	$	(16,242	)	$	(20,691	)
Reductions for securities sold during the period	792			2,746			4,730			3,472
Reductions for increases in cash flows expected to be collected that are recognized over the remaining life of the security	—			1			2			5
Balance of cumulative credit losses on debt securities, end of period	$	(11,510	)	$	(17,214	)	$	(11,510	)	$	(17,214	)

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 June 30, 2015:

	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)
U.S. Government sponsored agency securities	$	28,051	$	(130	)	$	—	$	—		$	28,051	$	(130	)
State and municipal securities	34,107		(387		)	—		—			34,107		(387		)
Corporate debt securities	7,965		(13		)	35,229		(4,754		)	43,194		(4,767		)
Collateralized mortgage obligations	95,315		(651		)	517,338		(17,142		)	612,653		(17,793		)
Mortgage-backed securities	306,980		(2,498		)	69,029		(1,368		)	376,009		(3,866		)
Auction rate securities	—		—			98,606		(7,898		)	98,606		(7,898		)
Total debt securities	472,418		(3,679		)	720,202		(31,162		)	1,192,620		(34,841		)
Equity securities	—		—			78		(12		)	78		(12		)
	$	472,418	$	(3,679	)	$	720,280	$	(31,174	)	$	1,192,698	$	(34,853	)

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:

	June 30, 2015				December 31, 2014
	Amortized cost		Estimated fair value		Amortized cost		Estimated fair value
	(in thousands)
Single-issuer trust preferred securities	$	47,613	$	43,378	$	47,569	$	42,016
Subordinated debt	47,595		49,716		47,530		50,023
Pooled trust preferred securities	—		530		2,010		4,088
Corporate debt securities issued by financial institutions	95,208		93,624		97,109		96,127
Other corporate debt securities	3,548		3,548		1,907		1,907
Available for sale corporate debt securities	$	98,756	$	97,172	$	99,016	$	98,034