Accumulated Other Comprehensive Income / (Loss) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Changes in accumulated other comprehensive income / (loss) by component, net of tax
Balance at beginning of period	$ 23,880	$ 104,547	$ (3,683)
Other comprehensive income before reclassifications	1,921	55,073	149,890
Amounts reclassified from accumulated other comprehensive income	(34,162)	(135,740)	(41,660)
Net current-period other comprehensive income	(32,241)	(80,667)	108,230
Balance at end of period	(8,361)	23,880	104,547
Net Gains/ (Losses) on Cash Flow Hedges
Changes in accumulated other comprehensive income / (loss) by component, net of tax
Balance at beginning of period	30,717	121,358	10,494
Other comprehensive income before reclassifications	(2,720)	53,815	163,704
Amounts reclassified from accumulated other comprehensive income	(34,548)	(144,456)	(52,840)
Net current-period other comprehensive income	(37,268)	(90,641)	110,864
Balance at end of period	(6,551)	30,717	121,358
Defined Benefit Pension and Postretirement Benefits
Changes in accumulated other comprehensive income / (loss) by component, net of tax
Balance at beginning of period	(6,837)	(16,811)	(14,122)
Other comprehensive income before reclassifications	4,641	1,258	(13,814)
Amounts reclassified from accumulated other comprehensive income	386	8,716	11,125
Net current-period other comprehensive income	5,027	9,974	(2,689)
Balance at end of period	(1,810)	(6,837)	(16,811)
Foreign Currency Translation Adjustment
Changes in accumulated other comprehensive income / (loss) by component, net of tax
Balance at beginning of period			(55)
Amounts reclassified from accumulated other comprehensive income			55
Net current-period other comprehensive income			$ 55

- Definition

Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

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