Quarterly Financial Data (unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Quarterly Financial Data (unaudited)
Total revenues	$ 350,733	$ 361,385	$ 349,004	$ 339,133	$ 328,877	$ 306,624	$ 298,705	$ 329,222	$ 1,400,255	$ 1,263,428	$ 1,084,386
Income net of noncontrolling interests and before gains on sale	3,956	28,577	98,749	19,962	2,516	9,713	22,101	74,750
Equity in net gain on sale of interest in unconsolidated joint venture/real estate	19,277	(4,807)	15,323	7,260	(114)	3,032			37,053	2,918	128,921
Purchase price fair value adjustment					8,306	999	475,102	13,788		498,195
Gain (loss) on early extinguishment of debt	(6,978)					(67)	971		(6,978)	904	(1,900)
Gain (loss) on sale of investment in marketable securities	2,703	2,237			4,999		(6)	(127)	4,940	4,866	490
Depreciable real estate reserves					(5,789)					(5,789)	(2,750)
Net income (loss) from discontinued operations	9,126	217	(67)	(160)	1,116	1,116	1,675	1,873	9,116	5,780	7,064
Gain on sale of discontinued operations				6,627			46,085		6,627	46,085	35,485
Net income attributable to SLGOP	28,084	26,224	114,005	33,689	11,034	14,793	545,928	90,284	202,002	662,039	305,149
Preferred unit redemption costs		(10,010)							(10,010)
Preferred unit distributions	(7,407)	(7,915)	(7,544)	(7,545)	(7,543)	(7,545)	(7,545)	(7,545)	(30,411)	(30,178)	(29,749)
Net income	$ 20,677	$ 8,299	$ 106,461	$ 26,144	$ 3,491	$ 7,248	$ 538,383	$ 82,739	$ 161,581	$ 631,861	$ 275,400
Net income per common unit-Basic (in dollars per share)	$ 0.23	$ 0.09	$ 1.15	$ 0.29	$ 0.03	$ 0.08	$ 6.30	$ 1.02	$ 1.75	$ 7.37	$ 3.47
Net income per common unit-Diluted (in dollars per share)	$ 0.23	$ 0.09	$ 1.14	$ 0.29	$ 0.03	$ 0.08	$ 6.26	$ 1.01	$ 1.74	$ 7.33	$ 3.45