Fair Value - by Balance Sheet Grouping (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013 Change During Period, Fair Value Disclosure [Member]	Sep. 30, 2012 Change During Period, Fair Value Disclosure [Member]	Sep. 30, 2013 MBS	Dec. 31, 2012 MBS	Sep. 30, 2013 Municipal Bonds	Dec. 31, 2012 Municipal Bonds	Sep. 30, 2013 Fair Value, Measurements, Nonrecurring [Member] Loans [Member] Carrying Amount [Member]	Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Loans [Member] Carrying Amount [Member]	Sep. 30, 2013 Fair Value, Measurements, Nonrecurring [Member] Mortgage Servicing Rights [Member] Carrying Amount [Member]	Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Mortgage Servicing Rights [Member] Carrying Amount [Member]	Sep. 30, 2013 Estimate of Fair Value, Fair Value Disclosure [Member] Fair Value, Measurements, Recurring [Member]	Dec. 31, 2012 Estimate of Fair Value, Fair Value Disclosure [Member] Fair Value, Measurements, Recurring [Member]	Sep. 30, 2013 Estimate of Fair Value, Fair Value Disclosure [Member] Fair Value, Measurements, Recurring [Member] MBS	Dec. 31, 2012 Estimate of Fair Value, Fair Value Disclosure [Member] Fair Value, Measurements, Recurring [Member] MBS	Sep. 30, 2013 Estimate of Fair Value, Fair Value Disclosure [Member] Fair Value, Measurements, Recurring [Member] Municipal Bonds	Dec. 31, 2012 Estimate of Fair Value, Fair Value Disclosure [Member] Fair Value, Measurements, Recurring [Member] Municipal Bonds	Sep. 30, 2013 Estimate of Fair Value, Fair Value Disclosure [Member] Fair Value, Measurements, Recurring [Member] Other [Member]	Dec. 31, 2012 Estimate of Fair Value, Fair Value Disclosure [Member] Fair Value, Measurements, Recurring [Member] Other [Member]	Sep. 30, 2013 Fair Value, Inputs, Level 1 [Member] Carrying Amount [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 1 [Member] Carrying Amount [Member]	Sep. 30, 2013 Fair Value, Inputs, Level 1 [Member] Estimate of Fair Value, Fair Value Disclosure [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 1 [Member] Estimate of Fair Value, Fair Value Disclosure [Member]	Sep. 30, 2013 Fair Value, Inputs, Level 1 [Member] Fair Value, Measurements, Recurring [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 1 [Member] Fair Value, Measurements, Recurring [Member]	Sep. 30, 2013 Fair Value, Inputs, Level 1 [Member] Fair Value, Measurements, Recurring [Member] MBS	Dec. 31, 2012 Fair Value, Inputs, Level 1 [Member] Fair Value, Measurements, Recurring [Member] MBS	Sep. 30, 2013 Fair Value, Inputs, Level 1 [Member] Fair Value, Measurements, Recurring [Member] Municipal Bonds	Dec. 31, 2012 Fair Value, Inputs, Level 1 [Member] Fair Value, Measurements, Recurring [Member] Municipal Bonds	Sep. 30, 2013 Fair Value, Inputs, Level 1 [Member] Fair Value, Measurements, Recurring [Member] Other [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 1 [Member] Fair Value, Measurements, Recurring [Member] Other [Member]	Sep. 30, 2013 Fair Value, Inputs, Level 1 [Member] Fair Value, Measurements, Nonrecurring [Member] Loans [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 1 [Member] Fair Value, Measurements, Nonrecurring [Member] Loans [Member]	Sep. 30, 2013 Fair Value, Inputs, Level 1 [Member] Fair Value, Measurements, Nonrecurring [Member] Mortgage Servicing Rights [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 1 [Member] Fair Value, Measurements, Nonrecurring [Member] Mortgage Servicing Rights [Member]	Sep. 30, 2013 Fair Value, Inputs, Level 2 [Member] Carrying Amount [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 2 [Member] Carrying Amount [Member]	Sep. 30, 2013 Fair Value, Inputs, Level 2 [Member] Estimate of Fair Value, Fair Value Disclosure [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 2 [Member] Estimate of Fair Value, Fair Value Disclosure [Member]	Sep. 30, 2013 Fair Value, Inputs, Level 2 [Member] Fair Value, Measurements, Recurring [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 2 [Member] Fair Value, Measurements, Recurring [Member]	Sep. 30, 2013 Fair Value, Inputs, Level 2 [Member] Fair Value, Measurements, Recurring [Member] MBS	Dec. 31, 2012 Fair Value, Inputs, Level 2 [Member] Fair Value, Measurements, Recurring [Member] MBS	Sep. 30, 2013 Fair Value, Inputs, Level 2 [Member] Fair Value, Measurements, Recurring [Member] Municipal Bonds	Dec. 31, 2012 Fair Value, Inputs, Level 2 [Member] Fair Value, Measurements, Recurring [Member] Municipal Bonds	Sep. 30, 2013 Fair Value, Inputs, Level 2 [Member] Fair Value, Measurements, Recurring [Member] Other [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 2 [Member] Fair Value, Measurements, Recurring [Member] Other [Member]	Sep. 30, 2013 Fair Value, Inputs, Level 2 [Member] Fair Value, Measurements, Nonrecurring [Member] Loans [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 2 [Member] Fair Value, Measurements, Nonrecurring [Member] Loans [Member]	Sep. 30, 2013 Fair Value, Inputs, Level 2 [Member] Fair Value, Measurements, Nonrecurring [Member] Mortgage Servicing Rights [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 2 [Member] Fair Value, Measurements, Nonrecurring [Member] Mortgage Servicing Rights [Member]	Sep. 30, 2013 Fair Value, Inputs, Level 3 [Member] Carrying Amount [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 3 [Member] Carrying Amount [Member]	Sep. 30, 2013 Fair Value, Inputs, Level 3 [Member] Estimate of Fair Value, Fair Value Disclosure [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 3 [Member] Estimate of Fair Value, Fair Value Disclosure [Member]	Sep. 30, 2013 Fair Value, Inputs, Level 3 [Member] Fair Value, Measurements, Recurring [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 3 [Member] Fair Value, Measurements, Recurring [Member]	Sep. 30, 2013 Fair Value, Inputs, Level 3 [Member] Fair Value, Measurements, Recurring [Member] MBS	Dec. 31, 2012 Fair Value, Inputs, Level 3 [Member] Fair Value, Measurements, Recurring [Member] MBS	Sep. 30, 2013 Fair Value, Inputs, Level 3 [Member] Fair Value, Measurements, Recurring [Member] Municipal Bonds	Dec. 31, 2012 Fair Value, Inputs, Level 3 [Member] Fair Value, Measurements, Recurring [Member] Municipal Bonds	Sep. 30, 2013 Fair Value, Inputs, Level 3 [Member] Fair Value, Measurements, Recurring [Member] Other [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 3 [Member] Fair Value, Measurements, Recurring [Member] Other [Member]	Sep. 30, 2013 Fair Value, Inputs, Level 3 [Member] Fair Value, Measurements, Nonrecurring [Member] Loans [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 3 [Member] Fair Value, Measurements, Nonrecurring [Member] Loans [Member]	Sep. 30, 2013 Fair Value, Inputs, Level 3 [Member] Fair Value, Measurements, Nonrecurring [Member] Mortgage Servicing Rights [Member]	Dec. 31, 2012 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]
Cash and cash equivalents																					$ 349,679,000	$ 331,550,000	$ 349,679,000	$ 331,550,000
Available for sale	1,498,377,000	1,513,157,000			1,305,456,000	1,308,838,000	192,749,000	204,306,000					1,498,377,000	1,513,157,000	1,305,456,000	1,308,838,000	192,749,000	204,306,000	172,000	13,000					0	0	0	0	0	0	0	0					1,498,377,000	1,513,157,000	1,498,377,000	1,513,157,000	1,498,377,000	1,513,157,000	1,305,456,000	1,308,838,000	192,749,000	204,306,000	172,000	13,000									0	0	0	0	0	0	0	0
Held to maturity	175,000	206,000																																			175,000	206,000	175,000	206,000
Loans held for sale	190,635,000	465,983,000	(12,532,000)	9,049,000									190,635,000	465,983,000											0	0											245,783,000	465,983,000	246,307,000	465,983,000	190,635,000	465,983,000															0	0
Loans receivable, net	26,931,000	23,177,000							76,193,000	172,172,000			26,931,000	23,177,000											0	0							0	0							0	0							0	0			7,024,326,000	6,101,749,000	7,058,375,000	6,154,296,000	26,931,000	23,177,000							76,193,000	172,172,000
Mortgage servicing rights, net	57,030,000	32,420,000																																																			57,030,000	32,420,000
Mortgage servicing rights, at fair value											57,030,000	32,420,000																							0	0															0	0			68,919,000	32,420,000											57,030,000	32,420,000
Other assets													7,443,000	11,183,000											0	0											102,602,000	108,642,000	102,602,000	108,642,000	7,443,000	11,183,000															0	0
Non-maturity deposits																																					5,111,524,000	4,697,147,000	5,111,524,000	4,697,147,000
Deposits with stated maturities																																					1,742,918,000	1,738,970,000	1,760,718,000	1,768,818,000
Borrowings																																					1,807,774,000	1,437,491,000	1,734,432,000	1,457,911,000
Other liabilities																																					6,236,000	4,025,000	6,236,000	4,025,000
FHLB stock	$ 95,200,000	$ 97,500,000