Investment Information - Other investments (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013
Schedule Of Other Investments [Line Items]
Other investments and fair value option investments	$ 1,226,741		$ 1,271,590
Available for sale
Schedule Of Other Investments [Line Items]
Other investments and fair value option investments	426,917		498,310
Available for sale | Asian and emerging markets
Schedule Of Other Investments [Line Items]
Other investments and fair value option investments	266,023		331,984
Available for sale | Investment grade fixed income
Schedule Of Other Investments [Line Items]
Other investments and fair value option investments	160,894		159,115
Available for sale | Other
Schedule Of Other Investments [Line Items]
Other investments and fair value option investments	0		7,211
Fair value option
Schedule Of Other Investments [Line Items]
Other investments and fair value option investments	799,824		773,280
Fair value option | Term loan investments
Schedule Of Other Investments [Line Items]
Other investments and fair value option investments	410,430		512,076
Other investments par	403,383		494,502
Fair value option | Asian and emerging markets
Schedule Of Other Investments [Line Items]
Other investments and fair value option investments	14,817		14,054
Fair value option | Investment grade fixed income
Schedule Of Other Investments [Line Items]
Other investments and fair value option investments	91,907		75,062
Fair value option | Other
Schedule Of Other Investments [Line Items]
Other investments and fair value option investments	$ 282,670	[1]	$ 172,088	[1]

[1] Includes fund investments with strategies in mortgage servicing rights, transportation and infrastructure assets and other.