Investment Securities (Summary Of Debt Securities By Contractual Maturity) (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]
Available for Sale, Amortized Cost - Due in one year or less	$ 15,518
Available for Sale, Amortized Cost - Due after one year through five years	107,131
Available for Sale, Amortized Cost - Due after five through ten years	260,350
Available for Sale, Amortized Cost - Due after ten years	2,470,071
Available for Sale, Amortized Cost - Total debt securities	2,853,070
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Available for Sale, Fair Value - Due in one year or less	15,546
Available for Sale, Fair Value - Due after one year through five years	111,200
Available for Sale, Fair Value - Due after five through ten years	260,884
Available for Sale, Fair Value - Due after ten years	2,486,256
Available for Sale, Fair Value - Total debt securities	2,873,886
Held-to-maturity Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis [Abstract]
Held to Maturity, Amortized Cost - Due in one year or less	15
Held to Maturity, Amortized Cost - Due after one year through five years	70,092
Held to Maturity, Amortized Cost - Due after five through ten years	67,799
Held to Maturity, Amortized Cost - Due after ten years	3,504,073
Held to Maturity, Amortized Cost - Total debt securities	3,641,979	3,358,721
Held-to-maturity Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Held to Maturity, Fair Value - Due in one year or less	15
Held-to-maturity, Fair Value, Due after one year through five years	73,095
Held to Maturity, Fair Value - Due after five through ten years	70,457
Held to Maturity, Fair Value - Due after ten years	3,556,258
Held to Maturity, Fair Value - Total debt securities	$ 3,699,825	$ 3,370,912