Short-Term Borrowings (Summary Of Short-Term Borrowings) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Short-term Debt [Member]
Short-term Debt [Line Items]
Year-end balance	$ 827,269	$ 346,987	$ 244,223
Security Owned and Sold, Not yet Purchased Fair Value, Security Sold, Not yet Purchased	25,321	30,158	24,230
Other short-term borrowings	500,000	0	1,200
Federal Funds Purchased [Member]
Short-term Debt [Line Items]
Average amount outstanding	$ 104,866	$ 105,910	$ 104,358
Weighted average rate	0.29%	0.18%	0.17%
Highest month-end balance	$ 147,900	$ 122,461	$ 124,093
Year-end balance	$ 105,563	$ 111,263	$ 100,193
Weighted average rate on outstandings at year-end	0.51%	0.25%	0.15%
Security Repurchase Agreements [Member]
Short-term Debt [Line Items]
Average amount outstanding	$ 311,045	$ 127,358	$ 116,190
Weighted average rate	0.23%	0.11%	0.06%
Highest month-end balance	$ 823,744	$ 205,566	$ 156,710
Year-end balance	$ 196,385	$ 205,566	$ 118,600
Weighted average rate on outstandings at year-end	0.26%	0.15%	0.13%