Borrowings (Summary Of Advances Payable To The Federal Home Loan Bank) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Federal Home Loan Bank, Advances, Maturity, Rolling Year [Abstract]
FHLB advances maturing within 1 year, Total Outstanding	$ 2,130,500	$ 2,025,934
FHLB advances maturing after 1 but within 2 years, Total Outstanding	200,000	500
FHLB advances maturing after 2 but within 3 years, Total Outstanding	128,026	200,000
FHLB advances maturing after 3 but within 4 years, Total Outstanding	175,000	103,026
FHLB advances maturing after 4 but within 5 years, Total Outstanding	200,000	175,000
FHLB advances maturing after 5 years, Total Outstanding	9,370	159,655
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Amount of Advances	2,842,896	2,664,115
Premiums on advances	12	24
Federal Home Loan Bank advances	$ 2,842,908	$ 2,664,139
Federal Home Loan Bank, Advances, Weighted Average Interest Rate [Abstract]
FHLB advances maturing within 1 year, Weighted-Average Contractual Coupon Rate (as a percent)	0.71%	0.55%
FHLB advances maturing after 1 but within 2 years, Weighted-Average Contractual Coupon Rate (as a percent)	1.36%	5.66%
FHLB advances maturing after 2 but within 3 years, Weighted-Average Contractual Coupon Rate (as a percent)	1.73%	1.36%
FHLB advances maturing after 3 but within 4 years, Weighted-Average Contractual Coupon Rate (as a percent)	1.77%	1.54%
FHLB advances maturing after 4 but within 5 years, Weighted-Average Contractual Coupon Rate (as a percent)	1.81%	1.77%
FHLB advances maturing after 5 years, Weighted-Average Contractual Coupon Rate (as a percent)	2.59%	1.60%
Federal Home Loan Bank, Advances, Weighted Average Interest Rate (as a percent)	0.95%	0.79%
Aggregate carrying value of assets pledged as collateral	$ 5,967,318	$ 5,719,746
Remaining borrowing capacity	$ 1,192,758	$ 1,203,057