Derivatives (Narrative) (Details)	3 Months Ended			3 Months Ended
	Mar. 31, 2014 USD ($) item security	Dec. 31, 2005 security	Dec. 31, 2001 security	Mar. 31, 2014 Standard & Poor's 500 Index [Member] USD ($) item security	Mar. 31, 2014 Standard & Poor's 500 Index [Member] Minimum [Member] USD ($)	Mar. 31, 2014 Standard & Poor's 500 Index [Member] Maximum [Member] USD ($)	Mar. 31, 2014 FTSE 100 Index [Member] USD ($) security item	Mar. 31, 2014 FTSE 100 Index [Member] GBP (£)
Derivative [Line Items]
Number of equity index put option contracts sold	7	7	7	6			1	1
Number of equity indices	2
Total consideration, net of commissions				$ 22,530,000			$ 6,706,000
Fair value of equity index put option contracts				30,516,000			6,567,000
Theoretical maximum payout occurs based on index value				0			0
Collateral rating threshold	0
Maturities range, years					12 years	30 years
Strike prices					1,141.21	1,540.63		5,989.75
Exercise date					June 2017	March 2031
Estimates the probability of equity index put option contract will falling below the strike price on the exercise date						25.00%	41.00%	41.00%
Discount factor				3.00%			3.00%	3.00%
Present value of theoretical maximum payouts				410,762,000			45,416,000
Derivative, net liability position, aggregate fair value	37,083,000
Collateral already posted, aggregate fair value	30,014,000
Required to post an additional approximation of the counterparties' fair value	55,000,000
Equity index if contracts had expired				1,872.34			6,598.40	6,598.40
Settlement amount if contracts had expired				$ 0			$ 0