Income Taxes - Jurisdictions the Company Remains Subject to Tax Examinations (Details)	12 Months Ended
	Dec. 31, 2017
Minimum | U.S. Federal
Income Tax Contingency [Line Items]
U.S. Federal	2014
Minimum | U.S. State
Income Tax Contingency [Line Items]
U.S. Federal	2014
Maximum | U.S. Federal
Income Tax Contingency [Line Items]
U.S. Federal	2016
Maximum | U.S. State
Income Tax Contingency [Line Items]
U.S. Federal	2016