Available-For-Sale Securities (Contractual Maturities Of Available-For-Sale Securities) (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Due in one year or less, Amortized Cost	$ 247,388	$ 188,594	$ 79,980
Due in one to five years, Amortized Cost	337,431	419,588	496,724
Due in five to ten years, Amortized Cost	357,677	361,037	106,545
Due after ten years, Amortized Cost	509,441	501,177	265,598
Total available-for-sale securities, Amortized Cost	1,867,574	1,785,113	1,866,314
Due in one year or less, Fair Value	247,836	189,015	80,351
Due in one to five years, Fair Value	338,633	419,654	494,391
Due in five to ten years, Fair Value	356,871	362,135	105,856
Due after ten years, Fair Value	507,152	503,999	264,102
Available-for-sale securities, at fair value	1,870,831	1,796,076	1,869,344
Collateralized Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available-for-sale securities, Amortized Cost	363,224	261,871	874,803
Available-for-sale securities, at fair value	368,282	271,574	886,148
Other equity securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available-for-sale securities, Amortized Cost	52,413	52,846	42,664
Available-for-sale securities, at fair value	$ 52,057	$ 49,699	$ 38,496