Derivatives (Narrative) (Details)	6 Months Ended	60 Months Ended
	Jun. 30, 2020 USD ($) Item	Dec. 31, 2005 Item	Dec. 31, 2019 USD ($)	Dec. 31, 2001 Item
Derivative [Line Items]
Number of equity indices | Item		2
Number of equity index put option contracts | Item		7		7
Equity index put option liability	$ 9,088,000		$ 5,584,000
Equity Index Put Option Contracts [Member]
Derivative [Line Items]
Equity index put option liability	0
Equity Index Put Option Contracts [Member] | Fair Value [Member]
Derivative [Line Items]
Equity index put option liability	$ 9,088,000		$ 5,584,000
Equity Index Put Option Contract, Expired On June 30, 2020 [Member]
Derivative [Line Items]
Number of equity index put option contracts expired | Item	5
Derivative expiration date	Jun. 30, 2020
Equity Index Put Option Contract, Expired On July 21, 2020 [Member]
Derivative [Line Items]
Derivative expiration date	Jul. 21, 2020
Standard & Poor's 500 Index [Member]
Derivative [Line Items]
Number of equity index put option contracts | Item	1
Theoretical maximum payout occurs based on index value	$ 0
Discount factor	3.00%
Present value of theoretical maximum payouts	$ 145,706,000
Settlement amount if contracts had expired	$ 0
Equity index if contracts had expired	3,100.29
Standard & Poor's 500 Index [Member] | Maximum [Member]
Derivative [Line Items]
Estimates the probability of equity index put option contract will falling below the strike price on the exercise date	0.80%
FTSE 100 Index [Member]
Derivative [Line Items]
Number of equity index put option contracts | Item	1
Derivative expiration date	Jul. 21, 2020
Equity index put option liability	$ 0