Derivatives (Cash Flow Hedges) (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Maximum Length of Time Hedged in Cash Flow Hedge	8 years	4 years
Derivative, Average Remaining Maturity	4 years 3 months 18 days	4 years 3 months 18 days
B [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Average Remaining Maturity	4 years 9 months 18 days	5 years
B [Member] | Single name credit default swaps (3)
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Average Remaining Maturity	6 months	0 years