Supplemental Disclosures to the Statements of Cash Flows (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Supplemental Disclosures to the Statements of Cash Flows
Cash payments for interest, net of $11,977,000, $9,675,000 and $3,355,000 capitalized in 2012, 2011 and 2010, respectively	$ 53,969	$ 46,847	$ 49,962
Interest cost capitalized	11,977	9,675	3,355
Cash payments for federal and state income taxes	1,200	925	655
In-kind distributions of Series A convertible preferred units	36,117	32,721	15,188
Unpaid change in liabilities for investing activities	26,742	18,194	2,750
Unpaid capital expenditures	$ 52,935	$ 26,193	$ 7,999