Borrowings (Summary Of Advances Payable To The Federal Home Loan Bank) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Federal Home Loan Bank, Advances, Maturity, Rolling Year [Abstract]
FHLB advances maturing within 1 year, Total Outstanding	$ 1,150,000	$ 2,130,500
FHLB advances maturing after 1 but within 2 years, Total Outstanding	103,026	200,000
FHLB advances maturing after 2 but within 3 years, Total Outstanding	215,000	128,026
FHLB advances maturing after 3 but within 4 years, Total Outstanding	200,000	175,000
FHLB advances maturing after 4 but within 5 years, Total Outstanding	170	200,000
FHLB advances maturing after 5 years, Total Outstanding	8,909	9,370
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Amount of Advances	1,677,105	2,842,896
Premiums on advances	0	12
Federal Home Loan Bank advances	$ 1,677,105	$ 2,842,908
Federal Home Loan Bank, Advances, Weighted Average Interest Rate [Abstract]
FHLB advances maturing within 1 year, Weighted-Average Contractual Coupon Rate (as a percent)	1.48%	0.71%
FHLB advances maturing after 1 but within 2 years, Weighted-Average Contractual Coupon Rate (as a percent)	1.81%	1.36%
FHLB advances maturing after 2 but within 3 years, Weighted-Average Contractual Coupon Rate (as a percent)	1.73%	1.73%
FHLB advances maturing after 3 but within 4 years, Weighted-Average Contractual Coupon Rate (as a percent)	4.13%	1.77%
FHLB advances maturing after 4 but within 5 years, Weighted-Average Contractual Coupon Rate (as a percent)	0.00%	1.81%
FHLB advances maturing after 5 years, Weighted-Average Contractual Coupon Rate (as a percent)	1.96%	2.59%
Federal Home Loan Bank, Advances, Weighted Average Interest Rate (as a percent)	1.85%	0.95%
Aggregate carrying value of assets pledged as collateral	$ 6,402,066	$ 5,967,318
Remaining borrowing capacity	$ 2,600,624	$ 1,192,758