Pension (Components Of Net Periodic Benefit Cost) (Detail) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Percentage Of Minimum Guaranteed Interest Received			5.00%
Percentage Of Automatic Non Discretionary Contribution Received By Employees			2.00%
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	$ 1,055,000	$ 1,149,000	$ 3,721,000	$ 3,551,000
Interest Cost	1,835,000	1,756,000	5,423,000	5,308,000
Expected Return On Plan Assets	(2,267,000)	(2,179,000)	(7,091,000)	(6,877,000)
Amortization Of Prior Service Cost	6,000	7,000	19,000	20,000
Amortization Of Transition Obligation	0	0	0	0
Amortization Of Net Actuarial (Gain) Or Loss	884,000	538,000	2,398,000	2,146,000
Net Periodic Postretirement Benefit Cost	1,513,000	1,271,000	4,470,000	4,148,000
Estimated Contributions, Next Fiscal Year					365,000
Contributions			274,000
Estimated Contributions, Current Fiscal Year			91,000
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	337,000	272,000	1,012,000	816,000
Interest Cost	217,000	201,000	651,000	603,000
Expected Return On Plan Assets	0	0	0	0
Amortization Of Prior Service Cost	29,000	29,000	86,000	85,000
Amortization Of Transition Obligation	2,000	28,000	6,000	85,000
Amortization Of Net Actuarial (Gain) Or Loss	42,000	16,000	126,000	47,000
Net Periodic Postretirement Benefit Cost	627,000	546,000	1,881,000	1,636,000
Estimated Contributions, Next Fiscal Year					621,000
Contributions			466,000
Estimated Contributions, Current Fiscal Year			155,000
SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	69,000	530,000	695,000	598,000
Interest Cost	100,000	109,000	304,000	258,000
Expected Return On Plan Assets	0	0	0	0
Amortization Of Prior Service Cost	54,000	100,000	163,000	155,000
Amortization Of Transition Obligation	0	0	0	0
Amortization Of Net Actuarial (Gain) Or Loss	52,000	(6,000)	165,000	103,000
Net Periodic Postretirement Benefit Cost	$ 275,000	$ 733,000	$ 1,327,000	$ 1,114,000