Fair Value Measurements (Summary of Gains and Losses on Level 3 Assets and Liabilities) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Trading Activity, Gains and Losses, Net [Line Items]
Total gains or losses included in earnings	$ 13,954	$ (5,567)
Change in unrealized gains or losses relating to assets still held at period end	14,512	(5,043)
Loans Fees And Sales [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Total gains or losses included in earnings	(45)	231
Change in unrealized gains or losses relating to assets still held at period end	535	580
Other Non-Interest Income [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Total gains or losses included in earnings	150	35
Change in unrealized gains or losses relating to assets still held at period end	128	35
Investment Securities Gains (Losses), Net [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Total gains or losses included in earnings	13,849	(5,833)
Change in unrealized gains or losses relating to assets still held at period end	$ 13,849	$ (5,658)