Fair Value Measurements (Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - Fair Value, Recurring [Member] - USD ($) $ in Thousands | Mar. 31, 2020 | Dec. 31, 2019 |
Level 1 [Member] | | |
Assets, Fair Value Disclosure [Abstract] | | |
Total assets | $ 523,210 | $ 516,775 |
Liabilities, Fair Value Disclosure [Abstract] | | |
Total liabilities | 0 | 0 |
Level 2 [Member] | | |
Assets, Fair Value Disclosure [Abstract] | | |
Total assets | 39,955 | 89,570 |
Liabilities, Fair Value Disclosure [Abstract] | | |
Total liabilities | 3,904 | 1,390 |
Level 3 [Member] | | |
Assets, Fair Value Disclosure [Abstract] | | |
Total assets | 1,000 | 1,000 |
Liabilities, Fair Value Disclosure [Abstract] | | |
Total liabilities | 0 | 0 |
Cash and Cash Equivalents [Member] | Cash [Member] | Level 1 [Member] | | |
Assets, Fair Value Disclosure [Abstract] | | |
Cash and cash equivalents | 390,789 | 474,756 |
Cash and Cash Equivalents [Member] | Cash [Member] | Level 2 [Member] | | |
Assets, Fair Value Disclosure [Abstract] | | |
Cash and cash equivalents | 0 | 0 |
Cash and Cash Equivalents [Member] | Cash [Member] | Level 3 [Member] | | |
Assets, Fair Value Disclosure [Abstract] | | |
Cash and cash equivalents | 0 | 0 |
Cash and Cash Equivalents [Member] | Money Market Funds [Member] | Level 1 [Member] | | |
Assets, Fair Value Disclosure [Abstract] | | |
Cash and cash equivalents | 132,421 | 42,019 |
Cash and Cash Equivalents [Member] | Money Market Funds [Member] | Level 2 [Member] | | |
Assets, Fair Value Disclosure [Abstract] | | |
Cash and cash equivalents | 0 | 0 |
Cash and Cash Equivalents [Member] | Money Market Funds [Member] | Level 3 [Member] | | |
Assets, Fair Value Disclosure [Abstract] | | |
Cash and cash equivalents | 0 | 0 |
Cash and Cash Equivalents [Member] | Corporate Securities [Member] | Level 1 [Member] | | |
Assets, Fair Value Disclosure [Abstract] | | |
Cash and cash equivalents | 0 | 0 |
Cash and Cash Equivalents [Member] | Corporate Securities [Member] | Level 2 [Member] | | |
Assets, Fair Value Disclosure [Abstract] | | |
Cash and cash equivalents | 1,671 | 8,993 |
Cash and Cash Equivalents [Member] | Corporate Securities [Member] | Level 3 [Member] | | |
Assets, Fair Value Disclosure [Abstract] | | |
Cash and cash equivalents | 0 | 0 |
Cash and Cash Equivalents [Member] | Agency Securities [Member] | Level 1 [Member] | | |
Assets, Fair Value Disclosure [Abstract] | | |
Cash and cash equivalents | | 0 |
Cash and Cash Equivalents [Member] | Agency Securities [Member] | Level 2 [Member] | | |
Assets, Fair Value Disclosure [Abstract] | | |
Cash and cash equivalents | | 19,993 |
Cash and Cash Equivalents [Member] | Agency Securities [Member] | Level 3 [Member] | | |
Assets, Fair Value Disclosure [Abstract] | | |
Cash and cash equivalents | | 0 |
Available-for-sale Securities [Member] | Corporate Securities [Member] | Level 1 [Member] | | |
Assets, Fair Value Disclosure [Abstract] | | |
Available-for-sale securities | 0 | 0 |
Available-for-sale Securities [Member] | Corporate Securities [Member] | Level 2 [Member] | | |
Assets, Fair Value Disclosure [Abstract] | | |
Available-for-sale securities | 36,551 | 47,884 |
Available-for-sale Securities [Member] | Corporate Securities [Member] | Level 3 [Member] | | |
Assets, Fair Value Disclosure [Abstract] | | |
Available-for-sale securities | 1,000 | 1,000 |
Available-for-sale Securities [Member] | Agency Securities [Member] | Level 1 [Member] | | |
Assets, Fair Value Disclosure [Abstract] | | |
Available-for-sale securities | 0 | 0 |
Available-for-sale Securities [Member] | Agency Securities [Member] | Level 2 [Member] | | |
Assets, Fair Value Disclosure [Abstract] | | |
Available-for-sale securities | 814 | 1,682 |
Available-for-sale Securities [Member] | Agency Securities [Member] | Level 3 [Member] | | |
Assets, Fair Value Disclosure [Abstract] | | |
Available-for-sale securities | 0 | 0 |
Available-for-sale Securities [Member] | Government securities [Member] | Level 1 [Member] | | |
Assets, Fair Value Disclosure [Abstract] | | |
Available-for-sale securities | | 0 |
Available-for-sale Securities [Member] | Government securities [Member] | Level 2 [Member] | | |
Assets, Fair Value Disclosure [Abstract] | | |
Available-for-sale securities | | 9,129 |
Available-for-sale Securities [Member] | Government securities [Member] | Level 3 [Member] | | |
Assets, Fair Value Disclosure [Abstract] | | |
Available-for-sale securities | | 0 |
Foreign Exchange Contract [Member] | Prepaid Expenses and Other Current Assets [Member] | Level 1 [Member] | | |
Assets, Fair Value Disclosure [Abstract] | | |
Prepaid expenses and other current assets | 0 | 0 |
Foreign Exchange Contract [Member] | Prepaid Expenses and Other Current Assets [Member] | Level 2 [Member] | | |
Assets, Fair Value Disclosure [Abstract] | | |
Prepaid expenses and other current assets | 919 | 1,889 |
Foreign Exchange Contract [Member] | Prepaid Expenses and Other Current Assets [Member] | Level 3 [Member] | | |
Assets, Fair Value Disclosure [Abstract] | | |
Prepaid expenses and other current assets | 0 | 0 |
Foreign Exchange Contract [Member] | Accrued Expenses and Other Current Liabilities [Member] | Level 1 [Member] | | |
Liabilities, Fair Value Disclosure [Abstract] | | |
Foreign currency derivatives | 0 | 0 |
Foreign Exchange Contract [Member] | Accrued Expenses and Other Current Liabilities [Member] | Level 2 [Member] | | |
Liabilities, Fair Value Disclosure [Abstract] | | |
Foreign currency derivatives | 3,904 | 1,390 |
Foreign Exchange Contract [Member] | Accrued Expenses and Other Current Liabilities [Member] | Level 3 [Member] | | |
Liabilities, Fair Value Disclosure [Abstract] | | |
Foreign currency derivatives | 0 | 0 |
Estimate of Fair Value Measurement [Member] | | |
Assets, Fair Value Disclosure [Abstract] | | |
Total assets | 564,165 | 607,345 |
Liabilities, Fair Value Disclosure [Abstract] | | |
Total liabilities | 3,904 | 1,390 |
Estimate of Fair Value Measurement [Member] | Cash and Cash Equivalents [Member] | Cash [Member] | | |
Assets, Fair Value Disclosure [Abstract] | | |
Cash and cash equivalents | 390,789 | 474,756 |
Estimate of Fair Value Measurement [Member] | Cash and Cash Equivalents [Member] | Money Market Funds [Member] | | |
Assets, Fair Value Disclosure [Abstract] | | |
Cash and cash equivalents | 132,421 | 42,019 |
Estimate of Fair Value Measurement [Member] | Cash and Cash Equivalents [Member] | Corporate Securities [Member] | | |
Assets, Fair Value Disclosure [Abstract] | | |
Cash and cash equivalents | 1,671 | 8,993 |
Estimate of Fair Value Measurement [Member] | Cash and Cash Equivalents [Member] | Agency Securities [Member] | | |
Assets, Fair Value Disclosure [Abstract] | | |
Cash and cash equivalents | | 19,993 |
Estimate of Fair Value Measurement [Member] | Available-for-sale Securities [Member] | Corporate Securities [Member] | | |
Assets, Fair Value Disclosure [Abstract] | | |
Available-for-sale securities | 37,551 | 48,884 |
Estimate of Fair Value Measurement [Member] | Available-for-sale Securities [Member] | Agency Securities [Member] | | |
Assets, Fair Value Disclosure [Abstract] | | |
Available-for-sale securities | 814 | 1,682 |
Estimate of Fair Value Measurement [Member] | Available-for-sale Securities [Member] | Government securities [Member] | | |
Assets, Fair Value Disclosure [Abstract] | | |
Available-for-sale securities | | 9,129 |
Estimate of Fair Value Measurement [Member] | Foreign Exchange Contract [Member] | Prepaid Expenses and Other Current Assets [Member] | | |
Assets, Fair Value Disclosure [Abstract] | | |
Prepaid expenses and other current assets | 919 | 1,889 |
Estimate of Fair Value Measurement [Member] | Foreign Exchange Contract [Member] | Accrued Expenses and Other Current Liabilities [Member] | | |
Liabilities, Fair Value Disclosure [Abstract] | | |
Foreign currency derivatives | $ 3,904 | $ 1,390 |