Investment Securities (Narrative) (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2015 USD ($) securities	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
Investments [Abstract]
Pledged to secure deposits | $	$ 2,130,000		$ 2,120,000
Other-than-temporary impairment charges | $	$ 88	$ 88
Number of securities in a loss position for less than twelve months	8
Number of securities in a loss position for twelve months or longer	32