Mortgage Banking Activities (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Principal balance of mortgage servicing rights
Mortgage loan portfolios service	$ 1,100,000	$ 1,100,000
FHLMC [Member]
Principal balance of mortgage servicing rights
Mortgage loan portfolios service	817,108	770,131
FNMA [Member]
Principal balance of mortgage servicing rights
Mortgage loan portfolios service	$ 316,142	$ 361,535