Debt (Schedule Of Credit Facilities) (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
Sep. 30, 2014	Dec. 31, 2013
Line of Credit Facility [Line Items]
Balance outstanding	$ 216,000	$ 0
Maximum balance outstanding during the period	270,000	265,500
Weighted average balance	141,393	61,642
Year-to-date weighted average interest rate (excluding facility fee)	0.80%	1.00%
Unsecured Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Balance outstanding	200,000	0
Available balance	296,946	497,821
Variable interest rate (excluding facility fee)	0.70%	0.00%
Letters of Credit [Member]
Line of Credit Facility [Line Items]
Balance outstanding	3,054	2,179
Unsecured And Uncommitted Overnight Facility [Member]
Line of Credit Facility [Line Items]
Balance outstanding	$ 16,000	$ 0
Variable interest rate (excluding facility fee)	1.30%	0.00%

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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