Members' Equity Members' Equity (AOCI) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ (11,933)	$ (25,672)
Deferred losses on interest rate swaps	(7,999)	772	(18,918)
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	12,896	13,133
Unrealized gain (loss) on available-for-sale securities	(63)	(166)	213
Ending balance	(7,099)	(11,933)	(25,672)
Unrealized Gain (Loss) on Derivative Instruments [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(11,873)	(25,778)
Deferred losses on interest rate swaps	(7,999)	772
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	12,896	13,133
Ending balance	(6,976)	(11,873)
Unrealized Gain (Loss) on Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(60)	106
Unrealized gain (loss) on available-for-sale securities	(63)	(166)
Ending balance	$ (123)	$ (60)