Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Statement of Cash Flows [Abstract]
NET CASH PROVIDED BY OPERATING ACTIVITIES	$ 99,495	$ 106,745
INVESTING ACTIVITIES
Proceeds from maturities and calls of securities held to maturity	897	1,227
Proceeds from sales of securities available for sale	92,413	7,061
Proceeds from maturities and calls of securities available for sale	408,079	580,791
Purchases of securities available for sale	(403,277)	(709,876)
Purchases of bank premises and equipment	(6,300)	(3,110)
Proceeds from sales of bank premises and equipment	11,428	201
Redemption of bank-owned life insurance policies	8,930	1,953
Purchases of other investment securities	(59,123)	(31,491)
Proceeds from sales and redemptions of other investment securities	42,282	22,332
Acquisition of Virginia Commerce Bancorp, Inc., net of cash paid	97,298	0
Net change in loans	(308,225)	(98,333)
NET CASH USED IN INVESTING ACTIVITIES	(115,598)	(229,245)
FINANCING ACTIVITIES
Cash dividends paid	(60,354)	(46,808)
Excess tax benefits from stock-based compensation arrangements	482	122
Acquisition of treasury stock	(2)	(92)
Proceeds from exercise of stock options	7,172	1,601
Repayment of long-term Federal Home Loan Bank borrowings	(421,390)	(26,402)
Proceeds from issuance of long-term Federal Home Loan Bank borrowings	775,000	275,000
Distribution of treasury stock for deferred compensation plan	81	77
Changes in:
Deposits	110,112	(147,182)
Federal funds purchased, securities sold under agreements to repurchase and other short-term borrowings	(220,345)	(23,854)
NET CASH PROVIDED BY FINANCING ACTIVITIES	190,756	32,462
Increase (Decrease) in cash and cash equivalents	174,653	(90,038)
Cash and cash equivalents at beginning of year	416,617	432,077
Cash and cash equivalents at end of period	$ 591,270	$ 342,039