Income Taxes (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
United States
Income Tax Examination [Line Items]
Net Earnings	$ 585,912
Illinois
Income Tax Examination [Line Items]
Net Earnings	$ (1,844)
North Carolina
Income Tax Examination [Line Items]
Net Earnings		$ 585
Connecticut
Income Tax Examination [Line Items]
Net Earnings			$ 1,616
Other Jurisdictions
Income Tax Examination [Line Items]
Net Earnings			$ 497