Investment Securities (Narrative) (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Investment Securities [Line Items]
Held to maturity, fair value	$ 2,027,197,000				$ 1,898,872,000				$ 2,027,197,000	$ 1,898,872,000
Available for sale	566,520,000				1,035,282,000				566,520,000	1,035,282,000
Trading Securities	21,938,000				31,894,000				21,938,000	31,894,000
Investment securities held to maturity	1,958,916,000				1,923,993,000				1,958,916,000	1,923,993,000
Investment securities available for sale	566,520,000				1,035,282,000				566,520,000	1,035,282,000
Trading investment securities	21,938,000				31,894,000				21,938,000	31,894,000
Available-for-sale securities, continuous unrealized loss position, fair value	177,517,000				183,259,000				177,517,000	183,259,000
Gross unrealized losses	49,745,000				20,972,000				49,745,000	20,972,000
Number of security positions in the securities held to maturity portfolio in an unrealized loss position	28				153				28	153
Fair value of investments held to maturity pledged as collateral	1,100,000,000								1,100,000,000
Weighted-average remaining expected life of residential mortgage-backed securities held to maturity, years	3.60								3.60
Number of security positions in the securities available for sale portfolio in an unrealized loss position	43				43				43	43
Amortized cost	598,837,000				1,014,006,000				598,837,000	1,014,006,000
Unrealized losses, available-for-sale securities	49,745,000				20,972,000				49,745,000	20,972,000
Unrealized losses, held to maturity securities	24,639,000				67,048,000				24,639,000	67,048,000
Fair value of securities available for sale pledged as collateral	385,000,000								385,000,000
Number of issuances of preferred securities									2
Weighted-average remaining expected life of residential mortgage-backed securities available for sale (years)	3.6								3.6
Impairment charges on securities									825,000	4,518,000	3,747,000
Equity securities carrying value	940,000								940,000
Unrealized gains	17,428,000				42,248,000				17,428,000	42,248,000
Gross gains realized on sales									31,456,000	8,615,000	8,006,000
Impairment charge part of combined amortized cost of the securities	18,300,000								18,300,000
Recognized impairment charges									829,000
Other-than-temporary impairment charges attributable to credit on trust preferred securities	18,300,000								18,300,000
Gains on securities transactions, net	12,034,000	863,000	16,492,000	2,679,000	6,967,000	112,000	3,656,000	863,000	32,068,000	11,598,000	8,005,000
Securities classified as available for sale									552,486,000	425,473,000	326,096,000
Interest income on trading securities									2,100,000	2,600,000	3,800,000
Pooled Trust Preferred Securities [Member]
Investment Securities [Line Items]
Available for sale	11,800,000								11,800,000
Investment securities available for sale	11,800,000								11,800,000
Number of security positions in the securities available for sale portfolio in an unrealized loss position	3								3
Amortized cost	20,000,000								20,000,000
Unrealized losses, available-for-sale securities	8,200,000								8,200,000
Other-than-temporarily impaired trust preferred securities, amortized cost									5,400,000
Other-than-temporarily impaired trust preferred securities, fair value	3,700,000								3,700,000
Specific Issuer Of Corporate Bond [Member]
Investment Securities [Line Items]
Number of security positions in the securities available for sale portfolio in an unrealized loss position	15								15
Amortized cost	10,000,000								10,000,000
Unrealized losses, available-for-sale securities	3,400,000								3,400,000
Perpetual Preferred Securities [Member]
Investment Securities [Line Items]
Amortized cost	35,000,000								35,000,000
Unrealized losses, available-for-sale securities	7,200,000								7,200,000
Single-Issuer Trust Preferred Securities [Member]
Investment Securities [Line Items]
Bank trust preferred securities type, trading securities					4					4
Private Label Mortgage-Backed Securities [Member]
Investment Securities [Line Items]
Number of security positions in the securities available for sale portfolio in an unrealized loss position	5								5
Number of private label mortgage-backed securities	17,000								17,000
Other-than-temporarily impaired mortgage-backed securities, amortized cost									52,300,000
Other-than-temporarily impaired mortgage-backed securities, fair value	50,200,000								50,200,000
Equity Securities [Member]
Investment Securities [Line Items]
Available for sale	41,953,000				47,808,000				41,953,000	47,808,000
Investment securities available for sale	41,953,000				47,808,000				41,953,000	47,808,000
Available-for-sale securities, continuous unrealized loss position, fair value	33,121,000				15,274,000				33,121,000	15,274,000
Gross unrealized losses	7,299,000				1,728,000				7,299,000	1,728,000
Amortized cost	47,932,000				48,724,000				47,932,000	48,724,000
Unrealized losses, available-for-sale securities	7,299,000				1,728,000				7,299,000	1,728,000
Impairment charges on securities											434,000
Unrealized gains	1,320,000				812,000				1,320,000	812,000
Number of impaired securities									6
Impaired Equity Securities [Member]
Investment Securities [Line Items]
Unrealized gains	217,000								217,000
Trust Preferred Securities [Member]
Investment Securities [Line Items]
Held to maturity, fair value	174,753,000				215,894,000				174,753,000	215,894,000
Investment securities held to maturity	193,312,000				269,368,000				193,312,000	269,368,000
Number of security positions in the securities held to maturity portfolio in an unrealized loss position	12								12
Amortized cost	46,400,000								46,400,000
Fair value	23,500,000								23,500,000
Unrealized losses, available-for-sale securities	22,900,000								22,900,000
Unrealized losses, held to maturity securities	22,867,000				59,365,000				22,867,000	59,365,000
Number of issuances of preferred securities									3
Impairment charges on securities									41,200,000
Other-than-temporarily impaired trust preferred securities, fair value	23,500,000								23,500,000
U.S. Treasury Securities [Member]
Investment Securities [Line Items]
Held to maturity, fair value	113,859,000				99,503,000				113,859,000	99,503,000
Investment securities held to maturity	100,018,000				100,161,000				100,018,000	100,161,000
Unrealized losses, held to maturity securities					909,000					909,000
Junior Subordinated Debt [Member]
Investment Securities [Line Items]
Number of security positions in the securities held to maturity portfolio in an unrealized loss position	12								12
Residential Mortgage-Backed Securities [Member]
Investment Securities [Line Items]
Held to maturity, fair value	1,230,993,000				1,142,116,000				1,230,993,000	1,142,116,000
Investment securities held to maturity	1,180,104,000				1,114,469,000				1,180,104,000	1,114,469,000
Gross unrealized losses	5,400,000								5,400,000
Unrealized losses, held to maturity securities	152,000				3,081,000				152,000	3,081,000
Gross gains on sales transactions									651,700,000
Private Label Mortgage-Backed Securities [Member]
Investment Securities [Line Items]
Gross unrealized losses	2,300,000								2,300,000
Investment Grade [Member] | Pooled Trust Preferred Securities [Member]
Investment Securities [Line Items]
Unrealized losses, available-for-sale securities	6,600,000								6,600,000
Investment Grade [Member] | Junior Subordinated Debt [Member]
Investment Securities [Line Items]
Number of security positions in the securities held to maturity portfolio in an unrealized loss position	5								5
Investment Grade [Member] | Private Label Mortgage-Backed Securities [Member]
Investment Securities [Line Items]
Gross unrealized losses	3,100,000								3,100,000
Non-Investment Grade [Member] | Junior Subordinated Debt [Member]
Investment Securities [Line Items]
Number of security positions in the securities held to maturity portfolio in an unrealized loss position	2								2
Not-Rated [Member] | Junior Subordinated Debt [Member]
Investment Securities [Line Items]
Number of security positions in the securities held to maturity portfolio in an unrealized loss position	5								5
Single-Issuer Trust Preferred Securities [Member]
Investment Securities [Line Items]
Bank trust preferred securities type, trading securities	3								3
Fair value of trading securities	$ 21,900,000				$ 31,900,000				$ 21,900,000	$ 31,900,000