Fair Value (Details) (USD $)	3 Months Ended		9 Months Ended			12 Months Ended
	Sep. 30, 2012		Sep. 30, 2012		Sep. 30, 2011	Dec. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Asset	$ 0		$ 11,779,000
Available for sale	2,049,961,000		2,049,961,000			2,547,876,000
Loans held for sale	199,879,000		199,879,000			223,638,000
Loans Receivable Held-for-sale, Net	320,823,000		320,823,000			273,957,000
Gain (Loss) on Mortgage Servicing Rights			(984,000)		4,253,000
Gains (Losses) on Sales of Other Real Estate			(32,000)		(17,380,000)
Mortgage servicing rights, net	26,819,000		26,819,000			23,102,000
Charge-offs for properties held			8,800,000			20,900,000
Contingent Consideration Liability [Roll Forward]
Beginning Balance	13,292,000		0
Valuation adjustments - noninterest expense - other - mergers and acquisitions	759,000		2,272,000
Ending Balance	14,051,000		14,051,000			0
Change During Period, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans held for sale	9,049,000		9,049,000			8,542,000
MBS [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	1,825,448,000		1,825,448,000
Municipal Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	205,405,000		205,405,000
Fair Value, Measurements, Nonrecurring [Member] | Loans [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gain (Loss) on Sales of Loans, Net			(25,960,000)			(47,372,000)
Fair Value, Measurements, Nonrecurring [Member] | Loans [Member] | Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans receivable, net	167,951,000		167,951,000			268,837,000
Fair Value, Measurements, Nonrecurring [Member] | OREO [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gains (Losses) on Sales of Other Real Estate			(3,232,000)			(10,860,000)
Fair Value, Measurements, Nonrecurring [Member] | OREO [Member] | Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other Real Estate Fair Value Disclosure	24,344,000		24,344,000			31,379,000
Fair Value, Measurements, Nonrecurring [Member] | Mortgage Servicing Rights [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gain (Loss) on Mortgage Servicing Rights			(983,000)			(6,191,000)
Fair Value, Measurements, Nonrecurring [Member] | Mortgage Servicing Rights [Member] | Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Servicing Asset at Fair Value, Amount	26,819,000		26,819,000			23,102,000
Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	2,049,961,000		2,049,961,000			2,547,876,000
Loans held for sale	320,823,000		320,823,000			223,638,000
Other assets	22,844,000		22,844,000			10,269,000
Assets, Fair Value Disclosure, Recurring	2,393,628,000		2,393,628,000			2,781,783,000
Other liabilities - derivatives	14,873,000		14,873,000			9,212,000
Total liabilities	28,924,000		28,924,000
Contingent Consideration Liability [Roll Forward]
Ending Balance	14,051,000		14,051,000
Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Measurements, Recurring [Member] | MBS [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	1,825,448,000		1,825,448,000			2,320,934,000
Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Measurements, Recurring [Member] | Municipal Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	205,405,000		205,405,000			207,456,000
Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Measurements, Recurring [Member] | Other [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	19,108,000		19,108,000			19,486,000
Fair Value, Inputs, Level 1 [Member] | Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	263,884,000		263,884,000			491,228,000
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	263,884,000		263,884,000			491,228,000
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Loans [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans receivable, net	0		0			0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Nonrecurring [Member] | OREO [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other Real Estate Fair Value Disclosure	0		0			0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Mortgage Servicing Rights [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Servicing Asset at Fair Value, Amount	0		0			0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	0		0			0
Loans held for sale	0		0			0
Other assets	0		0			0
Assets, Fair Value Disclosure, Recurring	0		0			0
Other liabilities - derivatives	0		0			0
Total liabilities	0		0
Contingent Consideration Liability [Roll Forward]
Ending Balance	0		0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | MBS [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	0		0			0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Municipal Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	0		0			0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Other [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	0		0			0
Fair Value, Inputs, Level 2 and Level 3 [Member] | Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other assets	121,187,000	[1]	121,187,000	[1]		109,317,000	[1]
Fair Value, Inputs, Level 2 and Level 3 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other assets	121,187,000	[1]	121,187,000	[1]		109,317,000	[1]
Fair Value, Inputs, Level 2 [Member] | Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	2,049,961,000		2,049,961,000			2,547,876,000
Held to maturity	1,716,000		1,716,000			1,747,000
Loans held for sale	320,823,000		320,823,000			273,957,000
Non-maturity deposits	4,690,350,000		4,690,350,000			3,824,948,000
Deposits with stated maturities	2,049,560,000		2,049,560,000			2,660,870,000
Borrowings	1,343,241,000		1,343,241,000			1,706,662,000
Other liabilities	14,873,000		14,873,000			9,212,000
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	2,049,961,000		2,049,961,000			2,547,876,000
Held to maturity	1,716,000		1,716,000			1,747,000
Loans held for sale	320,823,000		320,823,000			273,957,000
Non-maturity deposits	4,690,350,000		4,690,350,000			3,824,948,000
Deposits with stated maturities	2,088,695,000		2,088,695,000			2,710,740,000
Borrowings	1,333,925,000		1,333,925,000			1,724,347,000
Other liabilities	14,873,000		14,873,000			9,212,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Loans [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans receivable, net	0		0			0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Nonrecurring [Member] | OREO [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other Real Estate Fair Value Disclosure	0		0			0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Mortgage Servicing Rights [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Servicing Asset at Fair Value, Amount	0		0			0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	2,049,961,000		2,049,961,000			2,547,876,000
Loans held for sale						223,638,000
Loans Receivable Held-for-sale, Net	320,823,000		320,823,000
Other assets	22,844,000		22,844,000			10,269,000
Assets, Fair Value Disclosure, Recurring	2,393,628,000		2,393,628,000			2,781,783,000
Other liabilities - derivatives	14,873,000		14,873,000			9,212,000
Total liabilities	14,873,000		14,873,000
Contingent Consideration Liability [Roll Forward]
Ending Balance	0		0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | MBS [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	1,825,448,000		1,825,448,000			2,320,934,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Municipal Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	205,405,000		205,405,000			207,456,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Other [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	19,108,000		19,108,000			19,486,000
Fair Value, Inputs, Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
FHLB stock	98,300,000		98,300,000			99,000,000
Fair Value, Inputs, Level 3 [Member] | Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans receivable, net	5,990,365,000		5,990,365,000			5,341,179,000
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans receivable, net	6,016,644,000		6,016,644,000			5,347,555,000
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Loans [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans receivable, net	167,951,000		167,951,000			268,837,000
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Loans [Member] | Minimum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value Inputs, Selling Costs, Percent			4.50%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Loans [Member] | Maximum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value Inputs, Selling Costs, Percent			9.00%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | OREO [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other Real Estate Fair Value Disclosure	24,344,000		24,344,000			31,379,000
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | OREO [Member] | Minimum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value Inputs, Selling Costs, Percent			4.50%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | OREO [Member] | Maximum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value Inputs, Selling Costs, Percent			9.00%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Mortgage Servicing Rights [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Servicing Asset at Fair Value, Amount						23,102,000
Mortgage servicing rights, net	26,819,000		26,819,000
Weighted average prepayment speed			18.80%
Weighted average discount rate			10.20%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	0		0			0
Loans held for sale	0		0			0
Other assets	0		0			0
Assets, Fair Value Disclosure, Recurring	0		0			0
Other liabilities - derivatives	0		0			0
Total liabilities	14,051,000		14,051,000
Contingent Consideration Liability [Roll Forward]
Ending Balance	14,051,000		14,051,000
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | MBS [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	0		0			0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Municipal Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	0		0			0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available for sale	$ 0		$ 0			$ 0

[1] Other assets includes FHLB stock. As of September 30, 2012 and December 31, 2011, FHLB stock was carried at $98.3 million and $99.0 million, respectively