Significant Accounting Policies Significant Accounting Policies (Details) - USD ($) $ in Thousands |
3 Months Ended | ||
---|---|---|---|
Mar. 31, 2018 |
Mar. 31, 2017 |
Jan. 01, 2017 |
|
New Accounting Pronouncements or Change in Accounting Principle [Line Items] | |||
Decrease in cash inflows from cash flows provided by operating activities | $ 37,349 | $ (201,039) | |
Increase in cash flows used in investing activities | $ 704,719 | 8,896 | |
Accounting Standards Update 2016-15 | |||
New Accounting Pronouncements or Change in Accounting Principle [Line Items] | |||
Decrease in cash inflows from cash flows provided by operating activities | 20,000 | ||
Increase in cash flows used in investing activities | $ 20,000 | ||
Retained Earnings | Cumulative effect of adoption of ASU 2016-09 | |||
New Accounting Pronouncements or Change in Accounting Principle [Line Items] | |||
Cumulative effect of new accounting principle in period of adoption | $ 2,200 |