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           Derivative Instruments and Hedging Activities (Tables) 
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        3 Months Ended | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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           Mar. 31, 2015 
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| Derivative Instruments and Hedging Activities Disclosure [Abstract] | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Gains (Losses) Relating to Derivative Instruments Recorded in Other Comprehensive Income (Loss) | 
 The following table summarizes gains (losses) relating to derivative instruments recorded in other comprehensive income (loss) during the three months ended March 31, 2015 and 2014: 
 
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| Gains (Losses) Relating to Derivative Instruments Recorded to Income | 
 The following table summarizes gains (losses) relating to derivative instruments recorded to income during the three months ended March 31, 2015 and 2014: 
 
 
 
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| Gains (Losses) Relating to Derivative Instruments Reclassified from Accumulated Other Comprehensive Loss into Income Effective Portion | 
 The following table summarizes gains (losses) relating to derivative instruments reclassified from accumulated other comprehensive loss into income during the three months ended March 31, 2015 and 2014: 
 
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