Investment Securities (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Jun. 30, 2011	Sep. 30, 2010	Jun. 30, 2010	Dec. 31, 2010
Proceeds from sales and calls of securities available for sale				$ 763,500,000		$ 882,000,000
Gains on sales of securities available for sale			6,000,000		13,100,000
Losses on sales of securities available for sale			1,000,000		300,000
Gains associated with trading securities			1,000
Securities - available-for-sale, at fair value	2,253,089,000	2,190,804,000	2,253,089,000		2,190,804,000		1,960,222,000
Amount of other-than-temporary impairment recognized in earnings	140,000	39,000	1,872,000		4,441,000
Trading securities	2,794,000	0	2,794,000		0		0
Number of securities in security portfolio	1,060		1,060
Number of securities in unrealized loss position	64		64
Net unrealized losses	26,406,000		26,406,000				34,866,000
Number of securities rated	3	2	3		2
Credit losses recorded			500,000		300,000
Fair value of trust preferred securities		1,100,000			1,100,000
Collateralized Mortgage Obligations [Member] | Mortgage-Backed Securities - Non-Agency Group 1 [Member] | Non-Agency [Member]
Securities - available-for-sale, at fair value	95,100,000		95,100,000
Collateralized Mortgage Obligations [Member] | Non-Agency [Member]
Number of non-agency collateralized mortgage obligations	14		14
Net unrealized losses	3,500,000		3,500,000
Number of securities rated	10		10
Remaining fair value of non-agency mortgage backed securities	78,500,000		78,500,000
Investment Grade Range B- To CC [Member]
Number of securities rated	9		9
Investment Grade Rated B [Member]
Number of securities rated	1		1
Fair value	14,300,000		14,300,000
Investment Grade Rated B- [Member]
Number of securities rated	3		3
Investment Grade Rated CCC [Member]
Fair value	27,800,000		27,800,000
Investment Grade Rated CC [Member]
Number of securities rated	5		5
Fair value	36,400,000		36,400,000
Investment Grade Rated BB [Member]
Number of securities rated	1		1
Investment Grade Rated C [Member]
Number of securities rated	4		4
Investment Grade Rated D [Member]
Number of securities rated	2		2
Mortgage-Backed Securities - Agency [Member] | Non-Agency [Member]
Fair value		97,700,000			97,700,000
Credit losses recorded					3,000,000
Mortgage-Backed Securities - Non-Agency Group 1 [Member]
Securities - available-for-sale, at fair value							126,806,000
Number of securities with other-than-temporary impairment charges related to credit loss	3	10	3		10
Amount of other-than-temporary impairment recognized in earnings	0	39,000	499,000		2,997,000
Net unrealized losses							8,380,000
Pooled Trust Preferred Securities Group 1 [Member]
Securities - available-for-sale, at fair value	7,530,000		7,530,000	7,530,000			8,400,000
Number of securities with other-than-temporary impairment charges related to credit loss		2			2
Amount of other-than-temporary impairment recognized in earnings		0			311,000
Net unrealized losses	19,816,000		19,816,000				18,968,000
Number of securities rated	9		9
Fair value of trust preferred securities	7,500,000		7,500,000
Pooled Trust Preferred Securities And Non-Agency Mortgage Backed Securities [Member]
Amount of other-than-temporary impairment recognized in earnings					3,300,000
FASB ASC 325-10 (EITF 99-20) [Member]
Net unrealized losses	8,300,000		8,300,000
Number of securities rated	7		7
Fair value of trust preferred securities	4,800,000		4,800,000
Other-than-temporary-impairment losses on securities			0
Trust Preferred Securities Which Are Not Subject To FASB ASC 325-10 [Member]
Net unrealized losses	11,500,000	10,500,000	11,500,000		10,500,000
Number of securities rated		2			2
Fair value of trust preferred securities	2,700,000	3,600,000	2,700,000		3,600,000
Other-than-temporary-impairment losses on securities			0		0
Former Directors And Executives Of Monroe Bancorp [Member]
Trading securities	$ 2,800,000		$ 2,800,000