Income Taxes (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Taxes
Pre tax loss	$ (66,558)	$ (74,587)	$ (84,790)
Reconciliation between income taxes on income from continuing operations and statutory U.S. taxes
Statutory rate	(23,295)	(26,105)	(29,677)
State income tax net of federal benefit	(3,823)	(4,284)	(4,870)
Net change in valuation allowance	28,850	25,269	41,136
Gain on investment in Regulus Therapeutics Inc.		(6,353)
Tax credits	(15,839)	806	(4,202)
Noncontrolling interest			1,448
Deferred tax true-up	8,023	839	(4,236)
Other	170	719	412
Income Tax Expense (Benefit)	$ (5,914)	$ (9,109)	$ 11
Reconciliation between the effective tax rate on income from continuing operations and the statutory U.S. tax rate
Statutory rate (as a percent)	35.00%	35.00%	35.00%
State income tax net of federal benefit (as a percent)	5.70%	5.70%	5.70%
Net change in federal valuation allowance (as a percent)	(43.30%)	(33.90%)	(48.50%)
Gain on investment in Regulus Therapeutics Inc. (as a percent)		8.50%
Tax credits (as a percent)	23.80%	(1.10%)	5.00%
Noncontrolling interest (as a percent)			(1.70%)
Deferred tax true-up (as a percent)	(12.10%)	(1.10%)	5.00%
Other items (as a percent)	(0.20%)	(0.90%)	(0.50%)
Effective rate (as a percent)	8.90%	12.20%	0.00%