Income Taxes - Summary of components of net deferred income tax assets (liabilities) (Details 3) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred income tax assets
Inventory costs	$ 21,471	$ 29,453
Property, plant and equipment	12,333	0
Accrued employee benefits	22,595	34,472
Accrued operating expenses	42,290	24,904
Reserves	13,144	16,434
Investments	0	8,796
Loss carryforwards	68,518	91,832
Research and development and other credits	181,851	164,841
Capitalized research and development	97,975	83,224
Other	26,157	17,379
Total deferred income tax assets	486,334	471,335
Deferred income tax liabilities:
Property, plant and equipment	0	(571)
Investments	(1,970)	0
Other liabilities	(3,026)	(7,190)
Goodwill and intangible assets	(262,660)	(325,283)
Total deferred income tax liabilities	(267,656)	(333,044)
Net deferred income tax assets	218,678	138,291
Valuation allowance	(90,057)	(91,743)	$ (57,772)	$ (87,788)
Net deferred income tax assets	$ 128,621	$ 46,548