Debt And Credit Agreements (Narrative) (Details) - USD ($)		12 Months Ended
	Apr. 23, 2012	Dec. 31, 2015
Line of Credit Facility [Line Items]
Credit spread over LIBOR, basis points		1.75%
Line of credit facility, covenant terms, maximum debt to EBITDA ratio		3.0
Line of credit facility, covenant terms, minimum adjusted EBIT-to-interest expense ratio		2.5
Line of credit facility, covenant terms, maximum aggregate distributions		$ 100,000,000
Line of credit facility, covenant terms, percentage of distributions to net income		50.00%
Available credit under the Credit Agreement		$ 164,000,000
Unsecured Revolving Credit Facility
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 350,000,000
Debt Instrument, Term	5 years
Line of credit facility, option to increase additional amount	$ 75,000,000
Amount borrowed under the Credit Agreement	102,000,000
Previous Unsecured Revolving Credit Facility
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 300,000,000
Debt Instrument, Term	4 years