Collaborative Arrangements and Licensing Agreements, Satellite Company Collaborations - Regulus Therapeutics Inc. (Details) shares in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015 USD ($) shares	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	Dec. 31, 2015 USD ($) Drug shares	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Collaborative Arrangement and Licensing Agreement [Abstract]
Revenue earned	$ 51,571,000	$ 49,121,000	$ 120,428,000	$ 62,583,000	$ 84,861,000	$ 44,063,000	$ 57,076,000	$ 28,161,000	$ 283,703,000	$ 214,161,000	$ 147,285,000
Net carrying value	$ 24,792,000				$ 81,881,000				$ 24,792,000	81,881,000
Regulus Therapeutics Inc. [Member] | Satellite Company Collaborative Arrangement and Licensing Agreement [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Number of drugs currently in development | Drug									3
Revenue earned									$ 0	0	$ 0
Gain from sale of common stock									20,200,000	19,900,000
Total proceeds from sale of common stock									$ 25,500,000	$ 22,900,000
Common stock owned (in shares) | shares	2.8								2.8
Net carrying value	$ 24,800								$ 24,800
Regulus Therapeutics Inc. [Member] | Satellite Company Collaborative Arrangement and Licensing Agreement [Member] | Maximum [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Ownership interest percentage	5.00%								5.00%