Annual report pursuant to Section 13 and 15(d)

Significant Accounting Policies Significant Accounting Policies (Supplemental Cash Flow Information) (Details)

v3.8.0.1
Significant Accounting Policies Significant Accounting Policies (Supplemental Cash Flow Information) (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Supplemental Disclosure of Noncash Investing and Financing Activities [Abstract]      
Noncash or Part Noncash Acquisition, Fixed Assets Acquired $ 0 $ 0 $ 3,552