Derivative Financial Instruments (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Derivative [Line Items]
Impact On Interest Credited Changes In Actuarial Assumptions	$ (4.0)	$ (4.1)
S And P Five Hundred Index Options [Member]
Derivative [Line Items]
S&P 500 index options purchased per month	2
Expiry Date Of S And P Five Hundred Index Options Purchased Years	1 year 0 months 0 days
Derivative Option premiums paid	9.3	9.4
Amount received for derivative options exercised	20.1	19.3
Maximum credit exposure required increase in S&P 500 Index, percentage	4.50%
Interest Rate Swaps [Member]
Derivative [Line Items]
Collateral	$ 12.2