Investment Securities (Narrative) (Details) (USD $)	6 Months Ended	12 Months Ended				3 Months Ended	12 Months Ended										12 Months Ended
	Jun. 30, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Former Directors And Executives Of Monroe Bancorp [Member]	Mar. 31, 2011 Mortgage-Backed Securities - Non-Agency Group 1 [Member]	Dec. 31, 2011 Mortgage-Backed Securities - Non-Agency Group 1 [Member]	Dec. 31, 2010 Mortgage-Backed Securities - Non-Agency Group 1 [Member]	Dec. 31, 2009 Mortgage-Backed Securities - Non-Agency Group 1 [Member]	Dec. 31, 2010 Pooled Trust Preferred Securities [Member]	Dec. 31, 2011 Pooled Trust Preferred Securities [Member]	Dec. 31, 2009 Pooled Trust Preferred Securities [Member]	Dec. 31, 2011 FASB ASC 325-10 (EITF 99-20) [Member]	Dec. 31, 2010 FASB ASC 325-10 (EITF 99-20) [Member]	Dec. 31, 2011 Trust Preferred Securities Which Are Not Subject To FASB ASC 325-10 [Member]	Dec. 31, 2010 Trust Preferred Securities Which Are Not Subject To FASB ASC 325-10 [Member]	Dec. 31, 2011 States And Political Subdivisions [Member]	Dec. 31, 2010 States And Political Subdivisions [Member]	Dec. 31, 2011 Collateralized Mortgage Obligations [Member] Non-Agency [Member]	Dec. 31, 2010 Collateralized Mortgage Obligations [Member] Non-Agency [Member]	Dec. 31, 2011 Collateralized Mortgage Obligations [Member] Mortgage-Backed Securities - Non-Agency Group 1 [Member] Non-Agency [Member]	Dec. 31, 2010 Collateralized Mortgage Obligations [Member] Mortgage-Backed Securities - Non-Agency Group 1 [Member] Non-Agency [Member]	Dec. 31, 2011 Investment Grade Range B- To C [Member]	Dec. 31, 2010 Investment Grade Range B- To C [Member]	Dec. 31, 2011 Investment Grade Rated B [Member]	Dec. 31, 2010 Investment Grade Rated B- [Member]	Dec. 31, 2011 Investment Grade Rated CCC [Member]	Dec. 31, 2010 Investment Grade Rated CCC [Member]	Dec. 31, 2011 Investment Grade Rated CC [Member]	Dec. 31, 2010 Investment Grade Rated CC [Member]	Dec. 31, 2010 Investment Grade Rated BB [Member]	Dec. 31, 2011 Investment Grade Rated C [Member]	Dec. 31, 2010 Investment Grade Rated C [Member]	Dec. 31, 2010 Investment Grade Rated C [Member] Mortgage-Backed Securities - Non-Agency Group 1 [Member]	Dec. 31, 2010 Investment Grade Rated C [Member] Pooled Trust Preferred Securities [Member]	Dec. 31, 2011 Investment Grade Rated D [Member]	Dec. 31, 2010 Investment Grade Rated D [Member]	Dec. 31, 2011 Public And Other Funds [Member]	Dec. 31, 2010 Public And Other Funds [Member]
Investment [Line Items]
Proceeds from sales and calls of securities available for sale		$ 546,000,000	$ 481,500,000	$ 1,042,000,000
Gains on sales of securities available for sale		9,600,000	21,700,000	28,200,000
Losses on sales of securities available for sale		1,100,000	4,600,000	900,000
Gains associated with trading securities		21,000
Gain on investment securities included in realized gains		900,000	800,000	1,100,000
Investment securities		362,400,000	836,100,000	353,800,000													268,400,000	212,200,000																				835,000,000,000	1,481,000,000
Investment securities in shareholders' equity, percentage																	26.00%	24.10%
Available-for-sale portfolio transferred to held-to-maturity portfolio, fair value	143,800,000		143,800,000	230,100,000
Unrealized holding gain on available-for-sale portfolio transferred to held-to-maturity portfolio	9,400,000
Securities - available-for-sale, at fair value		2,071,276,000	1,960,222,000					126,806,000		8,400,000	7,327,000						402,844,000	348,924,000			85,900,000	126,800,000
Number of securities with other-than-temporary impairment charges related to credit loss								10	10	3	1	6
Amount of other-than-temporary impairment recognized in earnings		3,252,000	5,060,000	68,090,000			1,400,000	3,900,000	24,800,000
Trading securities		2,816,000			2,800,000
Number of securities in security portfolio		1,047
Number of securities in unrealized loss position		61
Number of non-agency collateralized mortgage obligations																			13	15
Net unrealized losses		25,592,000	34,866,000					8,380,000		18,968,000	18,134,000		7,000,000	8,800,000	11,100,000	10,200,000	193,000	2,549,000	4,500,000	7,400,000
Number of securities rated		3	10							9	8		6	7									9	8	1	1	2	4	4	2	1	4		1	5	2	1
Number of securities sold						1		2
Fair value																			73,200,000						13,800,000	8,300,000	24,200,000	28,100,000	14,000,000	25,100,000			8,800,000
Remaining fair value of non-agency mortgage backed securities																				70,300,000
Credit losses recorded		500,000	3,000,000
Fair value of trust preferred securities			8,400,000							1,800,000	7,300,000		4,200,000	4,400,000	3,100,000	4,000,000
Other-than-temporary-impairment losses on securities										$ 900,000