Net Income (Loss) Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended									12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014		Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Abstract]
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
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Weighted average shares outstanding - basic										103,061	100,612	97,917
Effect of dilutive securities (in shares):
Stock options										9,446	9,440	10,233
Restricted stock										477	425	433
Warrants										2,246	2,936	2,707
Dilutive potential shares										12,169	12,801	13,373
Weighted average shares - diluted (in shares)										115,230	113,413	111,290
Earnings Per Share, Basic and Diluted [Abstract]
Net income per share - basic	$ 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	$ 1.34	$ 1.82	$ 1.69	$ 0.66	$ 0.78	$ 0.73		$ 0.85	$ 0.61	$ 5.52	$ 2.98	$ 3.72
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted average number of shares										1,343	1,470	304
Convertible senior notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted average number of shares										994	4,247	4,761

[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.