Investment Securities OTTI Credit Losses (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Credit loss portion of other than temporary impairment
Credit-related other-than-temporary impairment	$ 0	$ (6,279)	$ (6,868)
Reduction due to credit impaired securities sold or adandoned	6,279	589
Private-Label Mortgage-Related Securities [Member]
Credit loss portion of other than temporary impairment
Credit-related other-than-temporary impairment	0	0	(532)
Reduction due to credit impaired securities sold or adandoned	0	532
Trust Preferred Debt Securities [Member]
Credit loss portion of other than temporary impairment
Credit-related other-than-temporary impairment	0	(6,279)	(6,336)
Reduction due to credit impaired securities sold or adandoned	$ 6,279	$ 57