Investments (Schedule of Fixed Maturity and Equity Securities) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012
Investment Holdings [Line Items]
Held for investment, amortized cost	$ 76,255	$ 76,088
Held for investment, fair value	60,840	61,521
Fixed Maturity Securities [Member] \| Available For Sale [Member]
Investment Holdings [Line Items]
Available for sale securities, amortized cost	26,527,730	21,957,027
Available for sale securities, gross unrealized gains	928,699	2,283,010
Available for sale securities, gross unrealized losses	(845,982)	(67,901)
Available for sale securities, fair value	26,610,447	24,172,136
Equity Securities, Available For Sale [Member] \| Available For Sale [Member]
Investment Holdings [Line Items]
Available for sale securities, amortized cost	7,503	44,598
Available for sale securities, gross unrealized gains	275	10,227
Available for sale securities, gross unrealized losses	0	(1,403)
Available for sale securities, fair value	7,778	53,422
United States Government Full Faith and Credit [Member] \| Fixed Maturity Securities [Member] \| Available For Sale [Member]
Investment Holdings [Line Items]
Available for sale securities, amortized cost	44,852	4,590
Available for sale securities, gross unrealized gains	367	564
Available for sale securities, gross unrealized losses	(2,294)	0
Available for sale securities, fair value	42,925	5,154
United States Government Sponsored Agencies [Member] \| Fixed Maturity Securities [Member] \| Available For Sale [Member]
Investment Holdings [Line Items]
Available for sale securities, amortized cost	1,313,776	1,763,789
Available for sale securities, gross unrealized gains	1,875	11,704
Available for sale securities, gross unrealized losses	(121,362)	(3,468)
Available for sale securities, fair value	1,194,289	1,772,025
United States Municipalities, States and Territories [Member] \| Fixed Maturity Securities [Member] \| Available For Sale [Member]
Investment Holdings [Line Items]
Available for sale securities, amortized cost	3,181,032	3,116,678
Available for sale securities, gross unrealized gains	164,785	461,770
Available for sale securities, gross unrealized losses	(39,074)	(125)
Available for sale securities, fair value	3,306,743	3,578,323
Foreign Government Obligations [Member] \| Fixed Maturity Securities [Member] \| Available For Sale [Member]
Investment Holdings [Line Items]
Available for sale securities, amortized cost	86,112	86,099
Available for sale securities, gross unrealized gains	8,907	19,160
Available for sale securities, gross unrealized losses	(3,462)	0
Available for sale securities, fair value	91,557	105,259
Corporate Securities [Member] \| Fixed Maturity Securities [Member] \| Available For Sale [Member]
Investment Holdings [Line Items]
Available for sale securities, amortized cost	17,142,118	12,930,173
Available for sale securities, gross unrealized gains	606,948	1,568,223
Available for sale securities, gross unrealized losses	(516,029)	(31,624)
Available for sale securities, fair value	17,233,037	14,466,772
Corporate Securities [Member] \| Fixed Maturity Securities [Member] \| Held For Investment [Member]
Investment Holdings [Line Items]
Held for investment, amortized cost	76,255	76,088
Held for investment, gross unrealized gains	0	0
Held for investment, gross unrealized losses	(15,415)	(14,567)
Held for investment, fair value	60,840	61,521
Residential Mortgage Backed Securities [Member] \| Fixed Maturity Securities [Member] \| Available For Sale [Member]
Investment Holdings [Line Items]
Available for sale securities, amortized cost	1,895,913	2,743,537
Available for sale securities, gross unrealized gains	119,230	172,304
Available for sale securities, gross unrealized losses	(43,183)	(27,728)
Available for sale securities, fair value	1,971,960	2,888,113
Commercial Mortgage Backed Securities [Member] \| Fixed Maturity Securities [Member] \| Available For Sale [Member]
Investment Holdings [Line Items]
Available for sale securities, amortized cost	1,821,988	354,870
Available for sale securities, gross unrealized gains	3,287	5,095
Available for sale securities, gross unrealized losses	(89,815)	(1,983)
Available for sale securities, fair value	1,735,460	357,982
Other Asset Backed Securities [Member] \| Fixed Maturity Securities [Member] \| Available For Sale [Member]
Investment Holdings [Line Items]
Available for sale securities, amortized cost	1,041,939	957,291
Available for sale securities, gross unrealized gains	23,300	44,190
Available for sale securities, gross unrealized losses	(30,763)	(2,973)
Available for sale securities, fair value	$ 1,034,476	$ 998,508

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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Amount of unrealized gain before deducting unrealized loss on investments in debt and equity securities classified as available-for-sale securities.

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Amount of unrealized loss before deducting unrealized gain on investments in available-for-sale securities.

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Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

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Fair value of investments in debt securities classified as held-to-maturity.

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Amount of unrecognized gain before loss on investments in held-to-maturity securities.

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Amount of unrecognized loss before gain on investments in held-to-maturity securities. Excludes write-down for other than temporary impairment (OTTI).

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