Annual report pursuant to Section 13 and 15(d)

Business and Summary of Significant Accounting Principles (Investments) (Details)

v3.8.0.1
Business and Summary of Significant Accounting Principles (Investments) (Details) - USD ($)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Accounting Policies [Abstract]      
Impairment of equity method investment $ 0 $ 0 $ 12,593,000
Impairment of cost-method investments $ 0 $ 0