Condensed Consolidated Statements of Comprehensive (Loss) Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Statement Of Partners Capital [Abstract]
Net (loss) income	$ (10,177)	$ 18,070	$ (12,966)	$ 64,612
Other comprehensive (loss) income, net of tax:
Unrealized gain (loss) on securities	99	(369)	967	(301)
Foreign currency translation adjustment	57	3	171	3
Income tax	(37)		(361)
Other comprehensive income (loss), net	119	(366)	777	(298)
Total comprehensive (loss) income	$ (10,058)	$ 17,704	$ (12,189)	$ 64,314