CONSOLIDATED STATEMENT OF CHANGES IN PARTNERS CAPITAL (USD $) In Thousands, unless otherwise specified	Total	General Partner Preferred Units	General Partner Units	Limited Partner Units	Accumulated Other Comprehensive Loss
Balance at Dec. 31, 2011	$ 1,081,992	$ 266,211	$ 737,914	$ 90,246	$ (12,379)
Increase (Decrease) in Partners' Capital [Roll Forward]
Issuance of General Partner Units, Net of Issuance Costs	134,436		134,436
Redemption of Preferred Units	(48,240)	(48,240)
Stock Based Compensation Activity	4,582		4,582
Conversion of Limited Partner Units to General Partner Units	0		4,763	(4,763)
Preferred Unit Distributions	(20,751)	(20,751)
Net Income (Loss)	(2,418)	20,751	(21,968)	(1,201)
Other Comprehensive Income (Loss)	5,550				5,550
Balance at Dec. 31, 2012	1,155,151	217,971	859,727	84,282	(6,829)
Increase (Decrease) in Partners' Capital [Roll Forward]
Issuance of General Partner Units, Net of Issuance Costs	173,785		173,785
Redemption of Preferred Units	(144,384)	(144,384)
Stock Based Compensation Activity	4,532		4,532
Conversion of Limited Partner Units to General Partner Units	0		996	(996)
Common Unit Distributions	(38,862)	0	(37,288)	(1,574)
Preferred Unit Distributions	(14,400)	(14,400)
Net Income (Loss)	41,433	14,400	25,912	1,121
Other Comprehensive Income (Loss)	3,467				3,467
Balance at Dec. 31, 2013	1,180,722	73,587	1,027,664	82,833	(3,362)
Increase (Decrease) in Partners' Capital [Roll Forward]
Redemption of Preferred Units	(73,587)	(73,587)
Stock Based Compensation Activity	2,948		2,948
Conversion of Limited Partner Units to General Partner Units	0		2,155	(2,155)
Common Unit Distributions	(47,263)	0	(45,447)	(1,816)
Preferred Unit Distributions	(2,481)	(2,481)
Net Income (Loss)	51,185	2,481	46,809	1,895
Other Comprehensive Income (Loss)	(11,014)				(11,014)
Balance at Dec. 31, 2014	$ 1,100,510	$ 0	$ 1,034,129	$ 80,757	$ (14,376)