Senior Notes (Schedule Of Outstanding Senior Notes) (Details) (USD $)		9 Months Ended		9 Months Ended
	May 24, 2013	Sep. 30, 2014 Senior Notes 5.4% [Member] Senior Notes [Member]	Dec. 31, 2013 Senior Notes 5.4% [Member] Senior Notes [Member]	Sep. 30, 2014 Senior Notes 4.868% [Member] Senior Notes [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Debt instrument, stated interest rate		5.40%	5.40%	4.868%
Date issued		Oct. 12, 2004		Jun. 05, 2014
Date due		Oct. 15, 2014		Jun. 01, 2044
Principal amounts	$ 329,897,000	$ 250,000,000		$ 400,000,000
Consolidated balance sheet amount		249,998,000	249,958,000	400,000,000
Market value		$ 250,485,000	$ 259,130,000	$ 395,824,000