Fair Value (Details - Level 3 narrative items) (USD $)	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012	Dec. 31, 2011
Fair Value - Other Details [Line Items]
Cash and cash equivalents	$ 1,261,540,000	$ 1,121,705,000	$ 1,512,418,000	$ 1,342,257,000
Accrued investment income	172,794,000	184,315,000
[FundsHeldDirectlyManagedMember]
Fair Value - Other Details [Line Items]
Cash and cash equivalents	20,200,000	53,700,000
Accrued investment income	8,300,000	10,200,000
Other net assets	143,700,000	33,600,000
[TradingSecuritiesMember] | [EquitySecuritiesMember]
Fair Value - Other Details [Line Items]
Fair Value Assets Level 2 To Level 1 Transfers Amount	0		1,100,000
[TradingSecuritiesMember] | [OtherInvestedAssetsMember]
Fair Value - Other Details [Line Items]
Aggregate carrying amount of other invested assets not carried at fair value	$ 241,900,000	$ 262,200,000