Investment Securities (Narrative) (Details) (USD $)	3 Months Ended													3 Months Ended
	Mar. 31, 2012 Y	Mar. 31, 2011	Dec. 31, 2011	Mar. 31, 2012 Pooled Trust Preferred Securities [Member]	Mar. 31, 2012 Trust Preferred Securities [Member]		Dec. 31, 2011 Trust Preferred Securities [Member]		Mar. 31, 2012 Residential Mortgage-Backed Securities [Member]	Dec. 31, 2011 Residential Mortgage-Backed Securities [Member]	Mar. 31, 2012 Perpetual Preferred Securities [Member]	Mar. 31, 2012 Private Label Mortgage-Backed Securities [Member]	Mar. 31, 2012 Single-Issuer Trust Preferred Securities [Member]	Dec. 31, 2011 Trust Preferred Securities [Member]	Mar. 31, 2012 Trust Preferred Securities [Member]	Mar. 31, 2012 Residential Mortgage-Backed Securities [Member]	Dec. 31, 2011 Residential Mortgage-Backed Securities [Member]	Mar. 31, 2012 U.S. Treasury Securities [Member]	Dec. 31, 2011 U.S. Treasury Securities [Member]	Mar. 31, 2012 Single-Issuer Trust Preferred Securities [Member]	Mar. 31, 2012 Investment Grade [Member] Pooled Trust Preferred Securities [Member]	Mar. 31, 2012 Investment Grade [Member] Specific Issuer Of Corporate Bond [Member]	Mar. 31, 2012 Investment Grade [Member] Trust Preferred Securities [Member]	Mar. 31, 2012 Investment Grade [Member] Private Label Mortgage-Backed Securities [Member]	Mar. 31, 2012 Non-Investment Grade [Member] Trust Preferred Securities [Member]	Mar. 31, 2012 Not-Rated [Member] Trust Preferred Securities [Member]	Mar. 31, 2012 Trust Preferred Securities [Member]	Mar. 31, 2012 Single-Issuer Trust Preferred Securities [Member]	Dec. 31, 2011 Single-Issuer Trust Preferred Securities [Member]
Investment Securities [Line Items]
Held to maturity, fair value	$ 1,940,444,000		$ 2,027,197,000											$ 174,753,000	$ 180,521,000	$ 1,133,217,000	$ 1,230,993,000	$ 110,564,000	$ 113,859,000
Available for sale	830,974,000		566,520,000		65,416,000	[1]	63,858,000	[1]	482,929,000	310,137,000
Trading investment securities	22,190,000		21,938,000
Number of security positions in the securities held to maturity portfolio in an unrealized loss position	29		28																	10			3		2	5
Fair value of investments held to maturity pledged as collateral	1,100,000,000
Weighted-average remaining expected life of residential mortgage-backed securities held to maturity, years	3.2
Number of security positions in the securities available for sale portfolio in an unrealized loss position	68		43	3							2		15											1
Amortized cost	845,916,000		598,837,000	20,000,000	86,935,000	[1]	96,956,000	[1]	476,729,000	304,631,000	10,000,000											10,000,000					46,400,000
Fair value				11,100,000																							34,900,000
Unrealized losses, available-for-sale securities	33,980,000		49,745,000		21,696,000		33,176,000		5,080,000	5,444,000	2,400,000	2,500,000			11,500,000						7,100,000	3,900,000		2,600,000			8,900,000
Unrealized losses, held to maturity securities	17,802,000		24,639,000											22,867,000	17,332,000	121,000	152,000
Fair value of securities available for sale pledged as collateral	239,000,000
Weighted-average remaining expected life of residential mortgage-backed securities available for sale, years	9.0
Impairment losses on securities		825,000												18,300,000
Non-credit impairment charges (before taxes)	11,500,000
Number of private label mortgage-backed securities												5
Other-than-temporarily impaired trust preferred securities, amortized cost	46,400,000
Bank trust preferred securities type, trading securities																												3
Securities classified as available for sale	8,335,000	105,987,000
Fair value of trading securities																												22,200,000	21,900,000
Interest income on trading securities	$ 422,000	$ 642,000

[1] Includes three pooled trust preferred securities, principally collateralized by securities issued by banks and insurance companies.