Debit and Credit Agreements (Additional Information) (Details)	Mar. 31, 2015	Dec. 31, 2014
7.33% weighted-average fixed rate notes
Debt Instrument [Line Items]
Long-term debt, weighted average interest rate	7.33%	7.33%
6.51% weighted-average fixed rate notes
Debt Instrument [Line Items]
Long-term debt, weighted average interest rate	6.51%	6.51%
9.78% fixed rate notes
Debt Instrument [Line Items]
Long-term debt, interest rate, stated percentage	9.78%	9.78%
5.58% weighted-average fixed rate notes
Debt Instrument [Line Items]
Long-term debt, weighted average interest rate	5.58%	5.58%
3.65% weighted-average fixed rate notes
Debt Instrument [Line Items]
Long-term debt, weighted average interest rate	3.65%	3.65%