Senior Notes (Schedule Of Outstanding Senior Notes) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Parent Company [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Debt instrument, stated interest rate	1.72%
Date Due	Dec. 31, 2023
Parent Company [Member] | Senior Notes [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Debt instrument, stated interest rate	4.868%	4.868%
Date Due	Jun. 01, 2044	Jun. 01, 2044
Senior Notes 5.4% [Member] | Senior Notes [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Debt instrument, stated interest rate	5.40%	5.40%
Date Issued	Oct. 12, 2004
Date Due	Oct. 15, 2014
Principal Amounts	$ 250,000,000
Senior Notes 4.868% [Member] | Senior Notes [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Debt instrument, stated interest rate	4.868%	4.868%
Date Issued	Jun. 05, 2014
Date Due	Jun. 01, 2044
Principal Amounts	$ 400,000,000
Consolidated Balance Sheet Amount	400,000,000	$ 400,000,000
Market value	$ 381,204,000	$ 404,892,000