Summary of Significant Accounting Policies Narrative (Details)	9 Months Ended
	Sep. 30, 2017 USD ($)
Employee Service Share-based Compensation, Tax Benefit Realized from Exercise of Stock Options (Deprecated 2017-01-31)	$ 123,000
Equity securities
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 6,500,000