Investments (Exposure To Concentrations Of Credit Risk) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 13,413,102	$ 11,697,394
Available-for-sale Securities	14,190,456	12,110,755
Canadian Province Of Quebec Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	1,030,000	1,041,000
Available-for-sale Securities	1,521,000	1,389,000
Canadian Province Of Ontario Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	996,000	1,023,000
Available-for-sale Securities	$ 1,312,000	$ 1,222,000