Investment Securities (Credit Loss Portion of OTTI Recognized in Earnings on Debt Securities) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Investment Securities [Abstract]
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Credit Losses on Debt Securities Held, Beginning Balance	$ 6,539	$ 6,197	$ 3,621
Addition: Credit losses on investment securities for which other-than-temporary impairment was not previously recognized	870	342	5,576
Reduction: credit losses on investment securities sold during the period	(2,959)		(3,000)
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Credit Losses on Debt Securities Held, Ending Balance	$ 4,450	$ 6,539	$ 6,197