Members' Equity Members' Equity - AOCI (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Accumulated other comprehensive loss, beginning balance			$ (25,672)	$ (20,154)
Other comprehensive income before reclassifications:
Deferred losses on interest rate swaps	9,660	(7,891)	5,593	(12,921)
Unrealized gain (loss) on available-for-sale securities	(54)	45	(116)	114
Other comprehensive income before reclasifications			5,477	(12,807)
Reclassification of deferred losses on interest rate swaps into income	3,368	3,174	6,475	6,295
Other comprehensive (loss) income for the period, net			11,952	(6,512)
Accumulated other comprehensive loss, ending balance	(13,720)	(26,666)	(13,720)	(26,666)
Interest Rate Swap [Member]
Other comprehensive income before reclassifications:
Deferred losses on interest rate swaps			5,593	(12,921)
Reclassification of deferred losses on interest rate swaps into income			6,475	6,295
Unrealized Losses on Interest Rate Swaps [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Accumulated other comprehensive loss, beginning balance			(25,778)	(20,047)
Other comprehensive income before reclassifications:
Other comprehensive income before reclasifications			5,593	(12,921)
Other comprehensive (loss) income for the period, net			12,068	(6,626)
Accumulated other comprehensive loss, ending balance	(13,710)	(26,673)	(13,710)	(26,673)
Unrealized Losses on Interest Rate Swaps [Member] | Interest Rate Swap [Member]
Other comprehensive income before reclassifications:
Deferred losses on interest rate swaps			5,593	(12,921)
Reclassification of deferred losses on interest rate swaps into income			6,475	6,295
Unrealized Gain (Loss) on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Accumulated other comprehensive loss, beginning balance			106	(107)
Other comprehensive income before reclassifications:
Unrealized gain (loss) on available-for-sale securities			(116)	114
Other comprehensive income before reclasifications			(116)	114
Other comprehensive (loss) income for the period, net			(116)	114
Accumulated other comprehensive loss, ending balance	$ (10)	$ 7	$ (10)	$ 7