Fair Value Measurement (Details 2) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Assets and Liabilities Measured at Fair Value on a Non-recurring Basis
Loans held for sale	$ 265,914	$ 255,201
Mortgage servicing rights	45,949	48,152	63,909
Fair Value, Inputs, Level 1 [Member]
Assets and Liabilities Measured at Fair Value on a Non-recurring Basis
Loans held for sale	0	0
Fair Value, Inputs, Level 2 [Member]
Assets and Liabilities Measured at Fair Value on a Non-recurring Basis
Loans held for sale	265,914	255,201
Fair Value, Inputs, Level 3 [Member]
Assets and Liabilities Measured at Fair Value on a Non-recurring Basis
Loans held for sale	0	0
Fair Value, Measurements, Nonrecurring [Member]
Assets and Liabilities Measured at Fair Value on a Non-recurring Basis
Impaired loans	115,741	178,669
Mortgage servicing rights	45,949	48,152
Loans held for sale	261,410	249,195
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 1 [Member]
Assets and Liabilities Measured at Fair Value on a Non-recurring Basis
Impaired loans	0	0
Mortgage servicing rights	0	0
Loans held for sale	0	0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member]
Assets and Liabilities Measured at Fair Value on a Non-recurring Basis
Impaired loans	0	0
Mortgage servicing rights	0	0
Loans held for sale	261,410	249,195
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
Assets and Liabilities Measured at Fair Value on a Non-recurring Basis
Impaired loans	115,741	178,669
Mortgage servicing rights	45,949	48,152
Loans held for sale	$ 0	$ 0