Investment Securities (Tables)

3 Months Ended

Mar. 31, 2020

Investments, Debt and Equity Securities [Abstract]

Amortized Cost, Unrealized Gains And Losses, And Fair Value Of Investment Securities

The following tables present the amortized cost, unrealized gains, unrealized losses and approximate fair values of debt securities at March 31, 2020 and December 31, 2019: 

	March 31, 2020
(in thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
Available for sale:
U.S. Treasury and agencies	$	691,066	$	59,446	$	—	$	750,512
Obligations of states and political subdivisions	242,262		10,172		(15)		252,419
Residential mortgage-backed securities and collateralized mortgage obligations	1,824,819		63,032		(307)		1,887,544
Total available for sale securities	$	2,758,147	$	132,650	$	(322)	$	2,890,475
Held to maturity:
Residential mortgage-backed securities and collateralized mortgage obligations	$	3,200	$	865	$	—	$	4,065
Total held to maturity securities	$	3,200	$	865	$	—	$	4,065

	December 31, 2019
(in thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
Available for sale:
U.S. Treasury and agencies	$	642,009	$	5,919	$	(4,324)	$	643,604
Obligations of states and political subdivisions	251,531		9,600		(37)		261,094
Residential mortgage-backed securities and collateralized mortgage obligations	1,896,708		18,962		(5,686)		1,909,984
Total available for sale securities	$	2,790,248	$	34,481	$	(10,047)	$	2,814,682
Held to maturity:
Residential mortgage-backed securities and collateralized mortgage obligations	$	3,260	$	1,003	$	—	$	4,263
Total held to maturity securities	$	3,260	$	1,003	$	—	$	4,263

Schedule Of Fair Value And Unrealized Losses Of Securities

Debt securities that were in an unrealized loss position as of March 31, 2020 and December 31, 2019 are presented in the following tables, based on the length of time individual securities have been in an unrealized loss position.

	March 31, 2020
	Less than 12 Months				12 Months or Longer				Total
(in thousands)	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Available for sale:
Obligations of states and political subdivisions	$	3,843	$	10	$	774	$	5	$	4,617	$	15
Residential mortgage-backed securities and collateralized mortgage obligations	—		—		22,719		307		22,719		307
Total	$	3,843	$	10	$	23,493	$	312	$	27,336	$	322

	December 31, 2019
	Less than 12 Months				12 Months or Longer				Total
(in thousands)	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Available for sale:
U.S. Treasury and agencies	$	313,169	$	4,324	$	—	$	—	$	313,169	$	4,324
Obligations of states and political subdivisions	4,611		30		1,906		7		6,517		37
Residential mortgage-backed securities and collateralized mortgage obligations	288,866		1,628		402,802		4,058		691,668		5,686
Total	$	606,646	$	5,982	$	404,708	$	4,065	$	1,011,354	$	10,047

Schedule Of Maturities Of Investment Securities

The following table presents the contractual maturities of debt securities at March 31, 2020:  

	Available For Sale				Held To Maturity
(in thousands)	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Due within one year	$	25,308	$	25,479	$	—	$	—
Due after one year through five years	53,243		54,215		3		3
Due after five years through ten years	851,403		908,128		11		12
Due after ten years	1,828,193		1,902,653		3,186		4,050
Total securities	$	2,758,147	$	2,890,475	$	3,200	$	4,065

Gain (Loss) on Securities [Table Text Block]

Investment Securities Pledged To Secure Borrowings And Public Deposits

The following table presents, as of March 31, 2020, investment securities which were pledged to secure borrowings, public deposits, and repurchase agreements as permitted or required by law: 

(in thousands)	Amortized Cost		Fair Value
To state and local governments to secure public deposits	$	283,422	$	292,225
Other securities pledged principally to secure repurchase agreements	552,246		580,377
Total pledged securities	$	835,668	$	872,602