Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating Loss Carryforwards [Line Items]
Deferred tax asset valuation allowance	$ 249,844	$ 134,782
Foreign tax credits	0	137,818
Unrecognized tax benefits	140,124	66,768	$ 47,534
Reduction in provision for income taxes due to impact of effective tax rate	86,000	$ 57,000
Research Tax Credit Carryforward
Operating Loss Carryforwards [Line Items]
Tax credit carryforward, amount	250,000
Valuation allowance	250,000
Federal tax authority
Operating Loss Carryforwards [Line Items]
Tax credit carryforward, amount	317,000
State tax authority
Operating Loss Carryforwards [Line Items]
Tax credit carryforward, amount	365,000
Foreign Tax Authority
Operating Loss Carryforwards [Line Items]
Tax credit carryforward, amount	135,000
Valuation allowance	$ 135,000