Investment Securities (Summary Of Debt Securities By Contractual Maturity) (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 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	104,048
Available for Sale, Amortized Cost - Due after five through ten years	127,779
Available for Sale, Amortized Cost - Due after ten years	3,014,667
Available for Sale, Amortized Cost - Total debt securities	3,246,694
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	106,689
Available for Sale, Fair Value - Due after five through ten years	128,197
Available for Sale, Fair Value - Due after ten years	3,013,108
Available for Sale, Fair Value - Total debt securities	3,248,194
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	61,934
Held to Maturity, Amortized Cost - Due after five through ten years	128,176
Held to Maturity, Amortized Cost - Due after ten years	2,939,664
Held to Maturity, Amortized Cost - Total debt securities	3,129,864
Held-to-maturity Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Held to Maturity, Fair Value - Due in one year or less	93
Held to Maturity, Fair Value - Due after one year through five years	65,296
Held to Maturity, Fair Value - Due after five through ten years	133,913
Held to Maturity, Fair Value - Due after ten years	2,974,846
Held to Maturity, Fair Value - Total debt securities	$ 3,174,148	$ 3,264,718