Common Stock Common Stock (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Class of Stock [Line Items]
Shares Issued During Period, Value, Share-based Compensation	$ 1.2
Sales Agency Agreements Common Stock, Shares Authorized	200,000,000	200,000,000
Document Period End Date	Jun. 30, 2017
Shares Issued During Period, Share-based Compensation	200,000
Sales Agency Agreement [Member]
Class of Stock [Line Items]
Shares issued		1,600,000
Sales Agency Agreements Common Stock, Shares Authorized	3,800,000
Common Stock Shares Authorized Under Sales Agency Agreements Remaining Shares Authorized To Sell	2,200,000