Interest Costs (Details) (USD $) In Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Interest Cost
Interest costs charged to expense	$ 75,316	$ 68,559	$ 229,730	$ 223,230
Interest costs capitalized	8,906	19,040	24,224	49,470
Total interest costs incurred	84,222	87,599	253,954	272,700
Interest Costs (Textual) [Abstract]
Non cash interest expense included in interest costs	$ 9,977	$ 10,689	$ 29,211	$ 32,983