Annual report pursuant to Section 13 and 15(d)

Basis of Presentation and Organization Recent Accounting Pronouncements (Details)

v3.8.0.1
Basis of Presentation and Organization Recent Accounting Pronouncements (Details) - USD ($)
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Operating Cash Flow Increase [Member]      
Item Effected [Line Items]      
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification $ 6,227,000 $ 5,538,000  
Income Tax Benefit [Member]      
Item Effected [Line Items]      
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification $ 6,082,000 $ 5,499,000 $ 7,925,000
Weighted Average Diluted Shares Outstanding Impact [Member]      
Item Effected [Line Items]      
Adoption of Recent Accounting Pronouncement Impact on Weighted Average Shares Outstanding 159,387 240,016