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		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Derivative [Line Items]
Contractual Rates	3.70%	3.53%	3.61%	3.46%
Rate Including Impact of Hedges	2.67%	2.73%	2.60%	2.66%