Available-For-Sale Securities (Contractual Maturities Of Available-For-Sale Securities) (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011
Schedule of Available-for-sale Securities [Line Items]
Due in one year or less, Amortized Cost	$ 83,658	$ 121,400
Due in one to five years, Amortized Cost	471,863	532,828
Due in five to ten years, Amortized Cost	135,580	95,279
Due after ten years, Amortized Cost	216,723	261,315
Total available-for-sale securities, Amortized Cost	1,243,376	1,284,733
Due in one year or less, Fair Value	83,863	121,662
Due in one to five years, Fair Value	471,747	530,632
Due in five to ten years, Fair Value	137,116	95,508
Due after ten years, Fair Value	217,087	264,321
Available-for-sale securities, at fair value	1,256,768	1,291,797	1,267,682
Collateralized Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available-for-sale securities, Amortized Cost	291,815	236,316
Available-for-sale securities, at fair value	306,238	248,551
Other equity securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available-for-sale securities, Amortized Cost	43,737	37,595
Available-for-sale securities, at fair value	$ 40,717	$ 31,123