Accumulated Other Comprehensive Loss (Details 1) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Unrealized gains/(losses) on available - for-sale securities , Beginning Balance	$ 0	$ 0	$ 0	$ 49
Unrealized gains/(losses) on available - for-sale securities, Current period change excluding amounts reclassified from other comprehensive loss	0	0	0	(181)
Unrealized gains/(losses) on available - for-sale securities, Amounts reclassified from accumulated other comprehensive loss	0	0	0	132
Unrealized gains/(losses) on available - for-sale securities, Total change in accumulated other comprehensive loss	0	0	0	(49)
Unrealized gains/(losses) on available - for-sale securities, Ending Balance	0	0	0	0
Unrealized losses on cash flow hedges, Beginning Balance	(62,980)	(70,664)	(59,263)	(98,937)
Unrealized losses on cash flow hedges, Current period change excluding amounts reclassified from other comprehensive loss	(55)	(2,788)	(13,637)	15,176
Unrealized losses on cash flow hedges, Amounts reclassified from accumulated other comprehensive loss	4,908	5,166	14,773	15,475
Unrealized losses on cash flow hedges, Total change in accumulated other comprehensive loss	4,853	2,378	1,136	30,651
Unrealized losses on cash flow hedges, Ending Balance	(58,127)	(68,286)	(58,127)	(68,286)
Items not yet recognized as a component of net periodic benefit cost (pension and other postretirement plans), Beginning Balance	(10,425)	(14,479)	(10,081)	(14,893)
Items not yet recognized as a component of net periodic benefit cost (pension and other postretirement plans), Current period change excluding amounts reclassified from other comprehensive loss	25	(446)	(319)	(32)
Items not yet recognized as a component of net periodic benefit cost (pension and other postretirement plans), Amounts reclassified from accumulated other comprehensive loss	0	0	0	0
Items not yet recognized as a component of net periodic benefit cost (pension and other postretirement plans), Total change in accumulated other comprehensive loss	25	(446)	(319)	(32)
Items not yet recognized as a component of net periodic benefit cost (pension and other postretirement plans), Ending Balance	(10,400)	(14,925)	(10,400)	(14,925)
Beginning Balance	(73,405)	(85,143)	(69,344)	(113,781)
Current period change excluding amounts reclassified from other comprehensive loss	(30)	(3,234)	(13,956)	14,963
Amounts reclassified from accumulated other comprehensive loss	4,908	5,166	14,773	15,607
Total change in accumulated other comprehensive loss	4,877	1,932	817	30,570
Ending Balance	$ (68,527)	$ (83,211)	$ (68,527)	$ (83,211)