Available For Sale Securities (Amortized Cost, Gross Unrealized Gains And Losses And Estimated Fair Value) (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2014	Dec. 31, 2013
Schedule of Investments [Line Items]
Amortized Cost	$ 1,874,193	$ 2,802,764
Gross Unrealized Gains	71,565	70,953
Gross Unrealized Losses	1,278	7,574
Estimated Fair Value	1,944,480	2,866,143
U.S. Government Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	945,739	1,781,052
Gross Unrealized Gains	136	226
Gross Unrealized Losses	3	12
Estimated Fair Value	945,872	1,781,266
Residential Mortgage-Backed Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	574,369	570,642
Gross Unrealized Gains	11,095	9,946
Gross Unrealized Losses	843	1,426
Estimated Fair Value	584,621	579,162
Commercial Mortgage-Backed Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	48,260	18,271
Gross Unrealized Gains	896	13
Gross Unrealized Losses	29	299
Estimated Fair Value	49,127	17,985
Other Asset-Backed Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	222,678	183,593
Gross Unrealized Gains	926	627
Gross Unrealized Losses	395	184
Estimated Fair Value	223,209	184,036
All Other Corporates [Member]
Schedule of Investments [Line Items]
Amortized Cost	38,041	50,933
Gross Unrealized Gains	335	267
Gross Unrealized Losses	8	37
Estimated Fair Value	38,368	51,163
Debt Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	1,829,087	2,604,491
Gross Unrealized Gains	13,388	11,079
Gross Unrealized Losses	1,278	1,958
Estimated Fair Value	1,841,197	2,613,612
Common Stocks: First Quantum Minerals Ltd [Member]
Schedule of Investments [Line Items]
Amortized Cost		154,281
Gross Unrealized Losses		5,616
Estimated Fair Value		148,665
Common Stocks: Banks, Trusts And Insurance Companies [Member]
Schedule of Investments [Line Items]
Amortized Cost	22,842	22,980
Gross Unrealized Gains	29,222	27,562
Estimated Fair Value	52,064	50,542
Common Stocks: Industrial, Miscellaneous And All Other [Member]
Schedule of Investments [Line Items]
Amortized Cost	22,264	21,012
Gross Unrealized Gains	28,955	32,312
Estimated Fair Value	51,219	53,324
Corporate Equity Securities [Member]
Schedule of Investments [Line Items]
Amortized Cost	45,106	198,273
Gross Unrealized Gains	58,177	59,874
Gross Unrealized Losses		5,616
Estimated Fair Value	$ 103,283	$ 252,531