Accounting Policies (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Accounting Standards Update 2016-01
Retained Earnings Adjustments [Line Items]
Impact of change in accounting policy		$ 0
Accounting Standards Update 2014-09
Retained Earnings Adjustments [Line Items]
Impact of change in accounting policy		(102)
Retained Earnings | Accounting Standards Update 2016-01
Retained Earnings Adjustments [Line Items]
Impact of change in accounting policy		331
Retained Earnings | Accounting Standards Update 2014-09
Retained Earnings Adjustments [Line Items]
Impact of change in accounting policy		$ (102)
Minimum | Accounting Standards Update 2016-02
Retained Earnings Adjustments [Line Items]
Impact of change in accounting policy	$ 7,000
Maximum | Accounting Standards Update 2016-02
Retained Earnings Adjustments [Line Items]
Impact of change in accounting policy	$ 9,000