Investment Securities Available for Sale (Narrative) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2014 USD ($)	Dec. 31, 2016 USD ($) securities	Dec. 31, 2015 USD ($)
Investments [Abstract]
Pledged to secure deposits | $		$ 2,040,000	$ 2,430,000
Securities in a loss position for less than twelve months | securities		88
Securities in a loss position for more than twelve months | securities		4
Other-than-temporary impairment charges | $	$ 88