Revenue (Deferred Revenue) (Details) - USD ($) $ in Thousands |
3 Months Ended | |
|---|---|---|
Mar. 31, 2018 |
Jan. 01, 2018 |
|
| Contract Asset [Member] | ||
| Capitalized Contract Cost [Line Items] | ||
| Adoption of ASC 606 | $ (40,854) | |
| Deferred Revenue [Member] | ||
| Capitalized Contract Cost [Line Items] | ||
| Balances at December 31, 2017 | $ 447,484 | |
| Adoption of ASC 606 | $ (105,933) | |
| Deferred revenue recognized | (120,820) | |
| Additional amounts deferred | 115,654 | |
| Balances at March 31, 2018 | $ 336,385 |