Summary of Significant Accounting Policies (Additional Cash Flow Information) (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Supplemental Cash Flow Information [Line Items]
Cash paid for interest	$ 29,378	$ 46,801	$ 56,924
Cash paid for income tax	58,950	54,437	62,830
Transfer of securities from available for sale to held to maturity	2,266,195
Unsettled purchases of securities	90,073
Loans foreclosed and transferred to other real estate owned and foreclosed assets	7,817	21,126	19,518
Loans to facilitate the sale of other real estate owned		75	480
Common stock/treasury stock issued to the Corporation's 401(k) stock purchase plan		$ 1,360	$ 9,770