Hedges and Derivative Financial Instruments (Narrative) (Details)	12 Months Ended
	Dec. 31, 2017 USD ($) contract	Dec. 31, 2016 contract
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Number of interest rate derivatives held (in contract) | contract	0	0
Derivative net hedge ineffectiveness	$ 0
Derivative instruments, loss reclassification from Accumulated OCI to income, estimated net amount to be transferred	$ 58,000,000