Consolidated Statement of Changes in Partners Capital - 6 months ended Jun. 30, 2015 - USD ($) $ in Thousands	Total	Total Partners' Capital	Common Units	Treasury Units	Partners' Capital	Accumulated Other Comprehensive Income	Non-controlling interests in Consolidated Entities
Balance at beginning of year at Dec. 31, 2014	$ 664,106	$ 494,859		$ (138,363)	$ 492,054	$ 2,805	$ 169,247
Balance at beginning of year (in shares) at Dec. 31, 2014	27,566,200		36,530,249	8,964,049
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income	$ 114,784	89,010			89,010		25,774
Unrealized (loss) gain on available-for-sale investments	(1,332)	(9,304)				(9,304)	7,972
Unrealized gain on derivative financial instruments	11	9				9	2
Currency translation adjustment	(167)	11				11	(178)
Changes in post-retirement benefit obligations	1,627	1,076				1,076	551
Acquisition of CoSine	12,842						12,842
Units issued and vesting of restricted units	3,091	3,091			3,091
Units issued and vesting of restricted units (shares)			146,959
Equity compensation- subsidiaries	2,860	1,766			1,766		1,094
Subsidiary's purchases of the Company's common units	(4,458)	(4,458)		$ (4,458)	(4,458)
Subsidiary's purchases of the Company's common units (in shares)				(249,632)
Purchases of SPLP common units	(1,917)	(1,917)		$ (1,917)	(1,917)
Purchases of SPLP common units (in shares)				(108,000)
Subsidiary's purchases of their common stock	(268)	237			237		(505)
Purchases of subsidiary shares from noncontrolling interests	(93)	(1,793)			(1,793)		1,700
Other, net	181	179			179		2
Balance at end of year at Jun. 30, 2015	$ 791,267	$ 572,766		$ (144,738)	$ 578,169	$ (5,403)	$ 218,501
Balance at end of period (in shares) at Jun. 30, 2015	27,355,527		36,677,208	9,321,681.000