Securities (Remaining Contractual Maturity Of Securities) (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Investment [Line Items]
Available-for-Sale Securities, Amortized Cost	$ 1,917,412	$ 1,742,094
Securities Available-for-Sale, Fair Value	1,961,099	1,765,366
Securities Held-to-Maturity, Amortized Cost	1,633,235	1,355,283
Securities Held-to-Maturity, Fair Value	1,661,724	1,351,241
U.S. Treasury, U.S. Agencies, state and municipal and foreign sovereign debt and other securities [Member]
Investment [Line Items]
Available-for-Sale Securities, One year or less, Amortized Cost	47,317
Available-for-Sale Securities, One year to five years, Amortized Cost	529,926
Available-for-Sale Securities, Five years to ten years, Amortized Cost	361,125
Available-for-Sale Securities, After ten years, Amortized Cost	43,013
Available-for-Sale Securities, One year or less, Fair Value	47,472
Available-for-Sale Securities, One year to five years, Fair Value	537,239
Available-for-Sale Securities, Five years to ten years, Fair Value	371,113
Available-for-Sale Securities, After ten years, Fair value	44,047
Held-to-Maturity Securities, One year or less, Amortized Cost	132
Held-to-Maturity Securities, One year to five years, Amortized Cost	622
Held-to-Maturity Securities, Five years to ten years, Amortized Cost	3,805
Held-to-Maturity Securities, After ten years, Amortized Cost	0
Held-to-Maturity Securities, One year or less, Fair Value	132
Held-to-Maturity Securities, One year to five years, Fair Value	623
Held-to-Maturity Securities, Five years to ten years, Fair Value	3,759
Held-to-Maturity Securities, After ten years, Fair Value	0
Collateralized mortgage obligations [Member]
Investment [Line Items]
Available-for-Sale Securities, All other securities, Without Single Maturity Date, Amortized Cost	79,157
Available-for-Sale Securities, Amortized Cost	79,157	97,260
Available-for-Sale Securities, All other securities, Without Single Maturity Date, Fair Value	82,265
Securities Available-for-Sale, Fair Value	82,265	99,972
Held-to-Maturity Securities, All other securities, Without Single Maturity Date, Amortized Cost	43,516
Securities Held-to-Maturity, Amortized Cost	43,516	50,708
Held-to-Maturity Securities, All other securities, Without Single Maturity Date, Fair Value	43,110
Securities Held-to-Maturity, Fair Value	43,110	48,979
Residential mortgage-backed securities [Member]
Investment [Line Items]
Available-for-Sale Securities, All other securities, Without Single Maturity Date, Amortized Cost	856,874
Available-for-Sale Securities, Amortized Cost	856,874	817,006
Available-for-Sale Securities, All other securities, Without Single Maturity Date, Fair Value	878,963
Securities Available-for-Sale, Fair Value	878,963	829,855
Held-to-Maturity Securities, All other securities, Without Single Maturity Date, Amortized Cost	1,307,065
Securities Held-to-Maturity, Amortized Cost	1,307,065	1,069,746
Held-to-Maturity Securities, All other securities, Without Single Maturity Date, Fair Value	1,329,862
Securities Held-to-Maturity, Fair Value	1,329,862	1,069,572
Commercial mortgage-backed securities [Member]
Investment [Line Items]
Available-for-Sale Securities, All other securities, Without Single Maturity Date, Amortized Cost	0
Available-for-Sale Securities, All other securities, Without Single Maturity Date, Fair Value	0
Held-to-Maturity Securities, All other securities, Without Single Maturity Date, Amortized Cost	278,095
Securities Held-to-Maturity, Amortized Cost	278,095	229,722
Held-to-Maturity Securities, All other securities, Without Single Maturity Date, Fair Value	284,238
Securities Held-to-Maturity, Fair Value	$ 284,238	$ 228,063