Investment Securities (Summary Of Debt Securities By Contractual Maturity) (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]
Available for Sale, Amortized Cost - Due in one year or less	$ 200
Available for Sale, Amortized Cost - Due after one year through five years	102,717
Available for Sale, Amortized Cost - Due after five through ten years	191,973
Available for Sale, Amortized Cost - Due after ten years	2,880,196
Available for Sale, Amortized Cost - Total debt securities	3,175,086
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Available for Sale, Fair Value - Due in one year or less	200
Available for Sale, Fair Value - Due after one year through five years	106,597
Available for Sale, Fair Value - Due after five through ten years	192,790
Available for Sale, Fair Value - Due after ten years	2,884,796
Available for Sale, Fair Value - Total debt securities	3,184,383
Held-to-maturity Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis [Abstract]
Held to Maturity, Amortized Cost - Due in one year or less	90
Held to Maturity, Amortized Cost - Due after one year through five years	66,262
Held to Maturity, Amortized Cost - Due after five through ten years	138,276
Held to Maturity, Amortized Cost - Due after ten years	3,001,371
Held to Maturity, Amortized Cost - Total debt securities	3,205,999
Held-to-maturity Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Held to Maturity, Fair Value - Due in one year or less	91
Held to Maturity, Fair Value - Due after one year through five years	69,780
Held to Maturity, Fair Value - Due after five through ten years	144,351
Held to Maturity, Fair Value - Due after ten years	3,034,398
Held to Maturity, Fair Value - Total debt securities	$ 3,248,620	$ 3,264,718