Income Taxes - (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax [Line Items]
Amounts impacting capital surplus	$ (0.4)	$ 0.2	$ 0.9
Tax computed at statutory rate	35.00%	35.00%	35.00%
Tax year audited	2013
State [Member] | 2004 Through 2016 Tax Years [Member]
Income Tax [Line Items]
Net operating loss carryforwards	$ 33.0
Operating loss carryforwards, originated tax years	2004 through 2016
Net operating loss carryforwards, expiration date	Dec. 31, 2019
Federal And State [Member] | From 2013 Through 2016 Tax Years [Member]
Income Tax [Line Items]
Tax credit carryforwards	$ 29.0
Tax credit carryforwards, originated tax years	2013 through 2016
Minimum [Member] | Federal And State [Member] | From 2013 Through 2016 Tax Years [Member]
Income Tax [Line Items]
Tax credit carryforwards, expiration date	Dec. 31, 2020
Maximum [Member] | Federal And State [Member] | From 2013 Through 2016 Tax Years [Member]
Income Tax [Line Items]
Tax credit carryforwards, expiration date	Dec. 31, 2035