Pension (Components Of Net Periodic Benefit Cost) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	$ 1,333	$ 1,201	$ 2,666	$ 2,402
Interest Cost	1,794	1,776	3,588	3,552
Expected Return On Plan Assets	(2,412)	(2,349)	(4,823)	(4,698)
Amortization Of Prior Service Cost	6	6	12	13
Amortization Of Transition Obligation	0	0	0	0
Amortization Of Net Actuarial (Gain) Or Loss	757	804	1,514	1,608
Net Periodic Postretirement Benefit Cost	1,478	1,438	2,957	2,877
Estimated Contributions, Next Fiscal Year					365
Contributions			183
Estimated Contributions, Current Fiscal Year	182		182
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	337	272	674	544
Interest Cost	217	201	434	402
Expected Return On Plan Assets	0	0	0	0
Amortization Of Prior Service Cost	29	28	58	56
Amortization Of Transition Obligation	2	28	4	57
Amortization Of Net Actuarial (Gain) Or Loss	42	16	84	31
Net Periodic Postretirement Benefit Cost	627	545	1,254	1,090
Estimated Contributions, Next Fiscal Year					621
Contributions			311
Estimated Contributions, Current Fiscal Year	310		310
SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	313	34	626	68
Interest Cost	102	75	204	149
Expected Return On Plan Assets	0	0	0	0
Amortization Of Prior Service Cost	54	28	109	55
Amortization Of Transition Obligation	0	0	0	0
Amortization Of Net Actuarial (Gain) Or Loss	57	54	113	109
Net Periodic Postretirement Benefit Cost	$ 526	$ 191	$ 1,052	$ 381