Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Contingency [Line Items]
Provisional tax expense		$ 172,100
Deferred Tax Assets, Operating Loss Carryforwards, Domestic	$ 27,122	41,282
Gross unrecognized tax benefits	30,554	48,604	$ 21,502	$ 38,992
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	19,700	23,400
Unrecognized tax benefits, income tax penalties and interest accrued	5,800	$ 4,900
Possible decrease in unrecognized tax benefits	$ 16,600
Maximum
Income Tax Contingency [Line Items]
IncomeTaxNetOperatingLossCarryforwardPeriod	20 years
2019 - 2023 [Member] | State and Local Jurisdiction [Member]
Income Tax Contingency [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration	$ 32,600
2024 - Thereafter [Member] | State and Local Jurisdiction [Member]
Income Tax Contingency [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration	$ 196,400
Accounting Standards Update 2016-09 [Member]
Income Tax Contingency [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption			$ 18,600