Fair Value - by Balance Sheet Grouping (Details) (USD $)	Dec. 31, 2013		Dec. 31, 2012
Fair Value, Balance Sheet Groupings, Financial Statement Captions [Line Items]
Available for sale	$ 1,429,812,000		$ 1,513,157,000
Fair Value	165,000		206,000
Loans receivable, net	26,462,000		23,177,000
Mortgage servicing rights, net	60,100,000		32,420,000
FHLB stock	95,300,000		97,500,000
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Balance Sheet Groupings, Financial Statement Captions [Line Items]
Cash and cash equivalents	545,435,000		331,550,000
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Balance Sheet Groupings, Financial Statement Captions [Line Items]
Available for sale	1,429,812,000		1,513,157,000
Fair Value	165,000		206,000
Loans held for sale	138,952,000		465,983,000
Other assets	99,756,000	[1]	108,642,000	[1]
Non-maturity deposits	5,373,544,000		4,697,147,000
Deposits with stated maturities	1,717,039,000		1,768,818,000
Borrowings	1,845,614,000		1,457,911,000
Other liabilities	516,000		4,025,000
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Balance Sheet Groupings, Financial Statement Captions [Line Items]
Loans receivable, net	7,344,637,000		6,154,296,000
Mortgage servicing rights, at fair value	75,017,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Balance Sheet Groupings, Financial Statement Captions [Line Items]
Cash and cash equivalents	545,435,000		331,550,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Balance Sheet Groupings, Financial Statement Captions [Line Items]
Available for sale	1,429,812,000		1,513,157,000
Fair Value	165,000		206,000
Loans held for sale	138,952,000		465,983,000
Other assets	99,756,000	[1]	108,642,000	[1]
Non-maturity deposits	5,373,544,000		4,697,147,000
Deposits with stated maturities	1,701,446,000		1,738,970,000
Borrowings	1,923,081,000		1,437,491,000
Other liabilities	516,000		4,025,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Balance Sheet Groupings, Financial Statement Captions [Line Items]
Loans receivable, net	7,331,228,000		6,101,749,000
Mortgage servicing rights, net	$ 60,100,000

[1] Other assets includes FHLB stock. As of December 31, 2013 and December 31, 2012, FHLB stock was carried at $95.3 million and $97.5 million, respectively