Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Other property and equipment, accumulated depreciation and amortization	$ 8,126	$ 7,446
Operating rights, amortization	4,731	4,509
Other assets, amortization	$ 13,996	$ 12,551
Limited partners' equity, units issued (in shares)	68,944,825	68,910,784
Limited partners' equity, units outstanding (in shares)	68,944,825	68,910,784
General partner's equity, percent	0.03%
Incentive Distribution Equity
Incentive distribution equity, units issued (in shares)	100,000	100,000
Incentive distribution equity, units outstanding (in shares)	100,000	100,000
Preferred Unit Series A
Preferred equity, units issued (in shares)	2,300,000	2,300,000
Preferred equity, units outstanding (in shares)	2,300,000	2,300,000
Preferred Unit Series B
Preferred equity, units issued (in shares)	7,200,000	7,200,000
Preferred equity, units outstanding (in shares)	7,200,000	7,200,000