Unaudited Quarterly Results (Details) $ / shares in Units, $ in Thousands	3 Months Ended									12 Months Ended
	Dec. 31, 2015 USD ($) $ / shares	Sep. 30, 2015 USD ($) $ / shares	Jun. 30, 2015 USD ($) $ / shares	Mar. 31, 2015 USD ($) $ / shares	Dec. 31, 2014 USD ($) $ / shares	Sep. 30, 2014 USD ($) $ / shares		Jun. 30, 2014 USD ($) $ / shares	Mar. 31, 2014 USD ($) $ / shares	Dec. 31, 2015 USD ($) $ / shares	Dec. 31, 2014 USD ($) $ / shares	Dec. 31, 2013 USD ($) $ / shares
Quarterly Financial Information Disclosure [Line Items]
Revenues	$ 1,098,077	$ 1,137,422	$ 998,617	$ 869,612	$ 802,329	$ 725,788		$ 665,700	$ 625,740	$ 4,103,728	$ 2,819,557	$ 2,104,745
Net income	$ 154,994	$ 210,398	$ 194,643	$ 76,021	$ 90,095	$ 83,375	[1]	$ 96,351	$ 68,305	$ 636,056	$ 338,126	$ 413,738
Net income per share - basic | $ / shares	$ 1.49	$ 2.04	$ 1.89	$ 0.74	$ 0.89	$ 0.83		$ 0.96	$ 0.69	$ 6.17	$ 3.36	$ 4.23
Net income per share - diluted | $ / shares	$ 1.34	$ 1.82	$ 1.69	$ 0.66	$ 0.78	$ 0.73		$ 0.85	$ 0.61	$ 5.52	$ 2.98	$ 3.72
Branded Prescription Drug Fee											$ 40,600
Antibody Collaboration
Quarterly Financial Information Disclosure [Line Items]
Number of families of novel antibodies												2
Up-front payments made to acquire full rights to antibodies										$ 0	$ 0	$ 20,000

[1] Net income in the third quarter of 2014 included a $40.6 million incremental charge related to the Branded Prescription Drug Fee based on final regulations issued by the IRS in July 2014 as described in Note 2 above.