Long-Term Debt (Narrative) (Details) (USD $)
|
12 Months Ended | ||
---|---|---|---|
Dec. 31, 2014
lender
|
Dec. 31, 2013
|
Dec. 31, 2012
|
|
Short-term Debt [Line Items] | |||
Maximum borrowing capacity | $ 600,000,000.0 | $ 600,000,000 | |
Number of lenders in syndicate | 12 | ||
Debt to equity ratio, max | 60.00% | ||
Debt to assets ratio, max | 15.00% | ||
Amount of assets, sold, transferred or disposed of in any trailing 4 quarters to total assets ratio, max | 25.00% | ||
Commercial paper | |||
Short-term Debt [Line Items] | |||
Maximum borrowing capacity | 600,000,000 | ||
Letters Of Credit | |||
Short-term Debt [Line Items] | |||
Maximum borrowing capacity | $ 250,000,000 |