Summary of Significant Accounting Policies (Investment Securities) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) security	Dec. 31, 2015
Accounting Policies [Abstract]
Percentage of investments recorded at fair value	94.00%	91.00%
Minimum percentage of variation expected	5.00%
Minimum variation expected | $	$ 1.0
Securities outside variance threshold | security	9