Investment Securities (Visa Class B Restricted Shares Narrative) (Details 8) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($) shares	Mar. 31, 2017 USD ($)
Net Investment Income [Line Items]
Gain on Sale of Investment Securities | $	$ 0	$ 12,467
Visa Class B Restricted Securities
Net Investment Income [Line Items]
Conversion Ratio to Class A shares	1.6483
Equity securities remaining, shares	86,614
Visa Class A Unrestricted Securities
Net Investment Income [Line Items]
Equity securities remaining, shares	142,766