Fair Value Measurements (Details 2) (USD $)			3 Months Ended	6 Months Ended
	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013 Derivative instruments, at fair value, net	Jun. 30, 2013 Derivative instruments, at fair value, net
Fair Value Assets and Liabilities Measured on Recurring Basis Unobservable Input Reconciliation
Balance at the beginning of the period			$ 69,865,000	$ 90,714,000
Total gains or losses included in earnings			(1,178,000)	(755,000)
Total gains or losses included in OCI			13,125,000	1,392,000
Purchases				72,000
Settlements			(7,124,000)	(16,735,000)
Balance at the end of the period			74,688,000	74,688,000
Unrealized gains and losses included in earnings			1,200,000	1,200,000
Estimated fair value of long-term debt	$ 2,900,000,000	$ 2,800,000,000