Credit Facilities (Narrative) (Details) (USD $)			6 Months Ended
Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2014 Mature On May 31, 2016 Debt_Covenants	Jun. 30, 2014 Mature On May 31, 2017 Debt_Covenants
Line of Credit Facility [Line Items]
Total of committed credit facilities with two banks	$ 250,000,000		$ 175,000,000	$ 75,000,000
Committed credit facilities maturity			May 31, 2016	May 31, 2017
Line of Credit Facility, Interest Rate	0.85%
Term of credit facility (years)			4 years	5 years
Borrowings outstanding	40,000,000	40,000,000
Stand-by letters of credit	$ 32,700,000
Number of financial covenants for debt agreements			2	2

- 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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