Fair Value (Activity Under Level 3, Fair Value Measurements Using Significant Unobservable Inputs By Asset Type) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 16,384	$ 2,847	$ 18,589	$ 5,054
Total gains or (losses) (realized/unrealized), Included in earnings (or changes in net assets)	43	(26)	81	87
Total gains or (losses) (realized/unrealized), Included in other comprehensive income (loss)	665	(45)	1,113	(240)
Purchases, issuances and settlements	(638)	2,479	11,044	2,457
Transfers in and/or (out) of Level 3	(3,911)	(376)	(18,284)	(2,479)
Ending balance	12,543	4,879	12,543	4,879
The amount of total gains or losses for the period included in earnings (or changes in net assets) attributable to the change in unrealized gains or losses relating to assets still held at the reporting date
Asset-backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	8,996	2,466	16,046	961
Total gains or (losses) (realized/unrealized), Included in earnings (or changes in net assets)	56	16	111	80
Total gains or (losses) (realized/unrealized), Included in other comprehensive income (loss)	390	(122)	728	(269)
Purchases, issuances and settlements	(61)	(19)	4,407	37
Transfers in and/or (out) of Level 3	(1,789)	(27)	(13,700)	1,505
Ending balance	7,592	2,314	7,592	2,314
The amount of total gains or losses for the period included in earnings (or changes in net assets) attributable to the change in unrealized gains or losses relating to assets still held at the reporting date
Foreign Corporate Debt Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	7,383		2,536	3,635
Total gains or (losses) (realized/unrealized), Included in earnings (or changes in net assets)	(14)	(3)	(33)	(3)
Total gains or (losses) (realized/unrealized), Included in other comprehensive income (loss)	275	(25)	387	(25)
Purchases, issuances and settlements	(576)	2,586	6,640	2,586
Transfers in and/or (out) of Level 3	(2,122)		(4,584)	(3,635)
Ending balance	4,946	2,558	4,946	2,558
The amount of total gains or losses for the period included in earnings (or changes in net assets) attributable to the change in unrealized gains or losses relating to assets still held at the reporting date
Non-agency Residential [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	5	381	7	458
Total gains or (losses) (realized/unrealized), Included in earnings (or changes in net assets)	1	(39)	3	10
Total gains or (losses) (realized/unrealized), Included in other comprehensive income (loss)		102	(2)	54
Purchases, issuances and settlements	(1)	(88)	(3)	(166)
Transfers in and/or (out) of Level 3		(349)		(349)
Ending balance	5	7	5	7
The amount of total gains or losses for the period included in earnings (or changes in net assets) attributable to the change in unrealized gains or losses relating to assets still held at the reporting date