Investment Securities - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended					3 Months Ended		9 Months Ended							9 Months Ended
	Sep. 30, 2013 Securities	Sep. 30, 2012	Sep. 30, 2013 Securities	Sep. 30, 2012	Dec. 31, 2012	Sep. 30, 2013 Former Directors and Executives of Monroe Bancorp [Member]	Dec. 31, 2012 Former Directors and Executives of Monroe Bancorp [Member]	Sep. 30, 2013 FASB ASC 325-10 (EITF 99-20) [Member] Securities	Sep. 30, 2012 FASB ASC 325-10 (EITF 99-20) [Member] Securities Security	Mar. 31, 2013 Pooled Trust Preferred Securities [Member] Security	Sep. 30, 2012 Pooled Trust Preferred Securities [Member]	Sep. 30, 2012 Pooled Trust Preferred Securities [Member]	Sep. 30, 2013 Pooled Trust Preferred Securities [Member] Securities	Dec. 31, 2012 Pooled Trust Preferred Securities [Member]	Sep. 30, 2013 Pooled Trust Preferred Securities [Member] Investment Grade Rated C [Member] Security	Sep. 30, 2013 Pooled Trust Preferred Securities [Member] Investment Grade Rated D [Member] Security	Sep. 30, 2013 Trust Preferred Securities which are Not Subject to FASB ASC 325-10 [Member] Security	Sep. 30, 2012 Trust Preferred Securities which are Not Subject to FASB ASC 325-10 [Member] Security	Sep. 30, 2013 Pooled Trust Preferred Securities and Non Agency Mortgage Backed Securities [Member]	Sep. 30, 2013 Mutual Funds [Member]	Sep. 30, 2012 Mortgage-Backed Securities - Non-Agency [Member] Security
Investment [Line Items]
Proceeds from sales and calls of securities available for sale			$ 334,400,000	$ 332,300,000
Gains on sales of securities available for sale			2,900,000		10,400,000					224,000
Losses on sales of securities available for sale			300,000
Gains associated with trading securities																			194,000	195,000	120,000
Number of securities with other-than-temporary impairment charges related to credit loss									1												6
Number of trust preferred securities													5				2	2			1
Other-than-temporary-impairment gains on securities			0	1,100,000																	1,100,000
Trading securities that consist of mutual funds	3,331,000	3,043,000	3,331,000	3,043,000	3,097,000	3,300,000	3,100,000
Available-for-sale portfolio transferred to held-to-maturity portfolio, fair value	357,800,000
Unrealized holding loss on available-for-sale portfolio transferred to held-to-maturity portfolio	31,000,000
Held-to-maturity securities transferred to available-for-sale		46,100,000		46,100,000
Number of securities in security portfolio	1,330		1,330
Number of securities in unrealized loss position	267		267
Pooled trust preferred security fair value								3,400,000					9,400,000				6,000,000	5,400,000
Net unrealized losses	61,410,000		61,410,000		19,880,000			5,400,000	7,300,000		476,000	476,000	13,518,000	15,525,000			8,100,000	8,900,000
Number of securities rated								3	6						1	2
Number of securities sold										1
Other-than-temporary impairment losses on pooled trust preferred security												165,000
Total other-than-temporary impairment losses		$ 202,000	$ 0	$ 1,078,000							$ 4,000	$ 165,000