Investment Securities (Summary Of Available For Sale Investment Securities By Maturity Groupings) (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Investment [Line Items]
Amortized Cost	$ 9,353,529	$ 9,691,414
Fair Value	9,552,179	9,777,004
U.S. Government And Federal Agency Obligations [Member]
Investment [Line Items]
Amortized Cost	697,677	729,846
Fair Value	715,310	727,076
U.S. Government And Federal Agency Obligations [Member] | Available For Sale Securities Maturity Within1 Year [Member]
Investment [Line Items]
Amortized Cost	58,866
Fair Value	60,127
U.S. Government And Federal Agency Obligations [Member] | Available For Sale Securities Maturity After1 But Within5 Years [Member]
Investment [Line Items]
Amortized Cost	498,613
Fair Value	514,076
U.S. Government And Federal Agency Obligations [Member] | Available For Sale Securities Maturity After5 But Within10 Years [Member]
Investment [Line Items]
Amortized Cost	104,754
Fair Value	108,327
U.S. Government And Federal Agency Obligations [Member] | Available For Sale Maturity After10 Years [Member]
Investment [Line Items]
Amortized Cost	35,444
Fair Value	32,780
Government-Sponsored Enterprise Obligations [Member]
Investment [Line Items]
Amortized Cost	713,485	794,912
Fair Value	721,658	793,023
Government-Sponsored Enterprise Obligations [Member] | Available For Sale Securities Maturity Within1 Year [Member]
Investment [Line Items]
Amortized Cost	10,680
Fair Value	10,754
Government-Sponsored Enterprise Obligations [Member] | Available For Sale Securities Maturity After1 But Within5 Years [Member]
Investment [Line Items]
Amortized Cost	572,163
Fair Value	579,157
Government-Sponsored Enterprise Obligations [Member] | Available For Sale Securities Maturity After5 But Within10 Years [Member]
Investment [Line Items]
Amortized Cost	125,012
Fair Value	126,156
Government-Sponsored Enterprise Obligations [Member] | Available For Sale Maturity After10 Years [Member]
Investment [Line Items]
Amortized Cost	5,630
Fair Value	5,591
State And Municipal Obligations [Member]
Investment [Line Items]
Amortized Cost	1,761,805	1,706,635
Fair Value	1,812,791	1,741,957
State And Municipal Obligations [Member] | Available For Sale Securities Maturity Within1 Year [Member]
Investment [Line Items]
Amortized Cost	99,478
Fair Value	99,618
State And Municipal Obligations [Member] | Available For Sale Securities Maturity After1 But Within5 Years [Member]
Investment [Line Items]
Amortized Cost	680,866
Fair Value	698,660
State And Municipal Obligations [Member] | Available For Sale Securities Maturity After5 But Within10 Years [Member]
Investment [Line Items]
Amortized Cost	916,693
Fair Value	948,352
State And Municipal Obligations [Member] | Available For Sale Maturity After10 Years [Member]
Investment [Line Items]
Amortized Cost	64,768
Fair Value	66,161
Agency Mortgage-Backed Securities [Member]
Investment [Line Items]
Amortized Cost	2,538,407	2,579,031
Fair Value	2,611,384	2,618,281
Non-Agency Mortgage-Backed Securities [Member]
Investment [Line Items]
Amortized Cost	852,059	879,186
Fair Value	863,158	879,963
Asset-Backed Securities [Member]
Investment [Line Items]
Amortized Cost	2,445,528	2,660,201
Fair Value	2,440,055	2,644,381
Total Mortgage And Asset-Backed Securities [Member]
Investment [Line Items]
Amortized Cost	5,835,994	6,118,418
Fair Value	5,914,597	6,142,625
Other Debt Securities [Member]
Investment [Line Items]
Amortized Cost	338,890	335,925
Fair Value	344,777	331,320
Other Debt Securities [Member] | Available For Sale Securities Maturity Within1 Year [Member]
Investment [Line Items]
Amortized Cost	9,327
Fair Value	9,341
Other Debt Securities [Member] | Available For Sale Securities Maturity After1 But Within5 Years [Member]
Investment [Line Items]
Amortized Cost	94,819
Fair Value	95,938
Other Debt Securities [Member] | Available For Sale Securities Maturity After5 But Within10 Years [Member]
Investment [Line Items]
Amortized Cost	222,744
Fair Value	227,750
Other Debt Securities [Member] | Available For Sale Maturity After10 Years [Member]
Investment [Line Items]
Amortized Cost	12,000
Fair Value	11,748
Equity Securities [Member]
Investment [Line Items]
Amortized Cost	5,678	5,678
Fair Value	$ 43,046	$ 41,003