Investments (Components of other-than-temporary impairment losses) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Gain (Loss) on Investments [Line Items]
Total other-than-temporary impairment net losses	$ 7		$ 229		$ 1,529
Non-credit portion of other-than-temporary impairment on available-for-sale debt securities	(212)		50		424
Net impairment losses recognized in earnings, available-for-sale	357	[1]	145	[1]	828	[1]
Available-for-sale Securities
Gain (Loss) on Investments [Line Items]
Total other-than-temporary impairment net losses	7		229		1,529
Non-credit portion of other-than-temporary impairment on available-for-sale debt securities	350	[2]	(84)	[2]	(701)	[2]
Net impairment losses recognized in earnings, available-for-sale	357	[3]	145	[3]	828	[3]
Available-for-sale Securities | Collateralized Mortgage Obligations | Non-Agency (below investment grade)
Gain (Loss) on Investments [Line Items]
Number of instruments with other than temporary impairments (in contracts)	2
Held-to-maturity Securities
Gain (Loss) on Investments [Line Items]
Total other-than-temporary impairment net losses	0		0		0
Portion of other-than-temporary impairment losses transferred from (recognized in) other comprehensive income, held-to-maturity securities	0	[2]	0	[2]	0	[2]
Net impairment losses recognized in earnings, held-to-maturity securities	$ 0	[3]	$ 0	[3]	$ 0	[3]

[1] Consisting of $7, $229 and $1,529 of total other-than-temporary impairment net losses, net of $(350), $84 and $701, recognized in other comprehensive income, for the years ended December 31, 2012, 2011 and 2010, respectively.

[2] Represents other-than-temporary impairment losses related to all other factors.

[3] Represents other-than-temporary impairment losses related to credit losses.