Derivative Financial Instruments - Contractual and Weighted-Average Interest Rates, Which Include the Effects of Hedges Related to Financial Instruments (Details) (Long-term debt)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Long-term debt
Derivative [Line Items]
Contractual Rates	3.53%	3.39%
Rate Including Impact of Hedges	2.54%	2.60%