Nature of Business and Accounting Policies - Cumulative Effect of applying ASC 606 to the Condensed Consolidated Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	$ 409,688	$ 311,224	$ 281,343
Inventories	124,360	111,740	111,830
Prepaid expenses and other current assets	140,819	149,958	167,124
Total assets	6,245,898	3,558,639	3,546,014
Accrued expenses	604,495	452,547	443,961
Early access sales accrual	354,404	225,128	232,401
Other liabilities, current portion	40,589	36,456	34,373
Accumulated other comprehensive income (loss)	659	(10,623)	(11,572)
Accumulated deficit	(2,989,478)	(5,111,443)	(5,119,723)
Total liabilities and shareholders’ equity	6,245,898	3,558,639	$ 3,546,014
Balances without Adoption of ASC 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	376,949
Inventories	124,506
Prepaid expenses and other current assets	167,522
Total assets	6,240,008
Accrued expenses	618,873
Early access sales accrual	380,609
Other liabilities, current portion	14,355
Accumulated other comprehensive income (loss)	927
Accumulated deficit	(3,009,985)
Total liabilities and shareholders’ equity	6,240,008
Effect of Change Higher/(Lower) | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	32,739	29,881
Inventories	(146)	(90)
Prepaid expenses and other current assets	(26,703)	(17,166)
Total assets	5,890	12,625
Accrued expenses	(14,378)	8,586
Early access sales accrual	(26,205)	(7,273)
Other liabilities, current portion	26,234	2,083
Accumulated other comprehensive income (loss)	(268)	949
Accumulated deficit	20,507	8,280
Total liabilities and shareholders’ equity	$ 5,890	$ 12,625