Fair Value Measurements (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Fair Value Assets and Liabilities Measured on Recurring Basis Unobservable Input Reconciliation
Estimated fair value of long-term debt	$ 2,800,000,000	$ 2,900,000,000
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	90,714,000	143,260,000
Total gains or losses included in earnings	640,000	(615,000)
Total gains or losses included in OCI	(2,554,000)	23,386,000
Purchases		(933,000)
Settlements	(34,381,000)	(74,384,000)
Transfers in and/or out of Level 3	(54,419,000)
Balance at the end of the period		90,714,000
Unrealized gains and losses included in earnings	$ 0	$ 0