Shareholders' Equity And Earnings Per Share (Aggregate Fair Values Assigned To Each Component Of Tangible Equity Units Offering) (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2010	Dec. 07, 2010
Trading Activity, Gains and Losses, Net [Line Items]
Units issued		4,600	[1]
Unit price		$ 50
Gross proceeds		$ 230,000
Issuance costs, including discount		7,353
Carrying value of Tangible Equity Units, Net proceeds	222,647
Other Borrowings [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Carrying value of Tangible Equity Units, Net proceeds	43,331
Surplus [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Carrying value of Tangible Equity Units, Net proceeds	179,316
Equity [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Units issued		4,600	[1]
Unit price		$ 40.271818
Gross proceeds		185,250
Issuance costs, including discount		5,934
Carrying value of Tangible Equity Units, Net proceeds	179,316
Equity [Member] | Other Borrowings [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Carrying value of Tangible Equity Units, Net proceeds	0
Equity [Member] | Surplus [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Carrying value of Tangible Equity Units, Net proceeds	179,316
Debt [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Units issued		4,600	[1]
Unit price		$ 9.728182
Gross proceeds		44,750
Issuance costs, including discount		1,419
Carrying value of Tangible Equity Units, Net proceeds	43,331
Debt [Member] | Other Borrowings [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Carrying value of Tangible Equity Units, Net proceeds	43,331
Debt [Member] | Surplus [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Carrying value of Tangible Equity Units, Net proceeds	$ 0

[1] TEUs consist of two components: one unit of the equity component and one unit of the debt component.