Annual report pursuant to Section 13 and 15(d)

Held-to-Maturity Securities (Details Textuals)

Held-to-Maturity Securities (Details Textuals) (USD $)
12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Schedule of Held-to-maturity Securities [Line Items]      
Available for sale securities transferred to held to maturity securities $ 469,100,000    
Purchases of held-to-maturity securities 204,082,000 0 0
Held-to-Maturity Securities (Textuals)      
Unrealized net losses recognized in OCI at time of transfer of available for sale securities transferred to Held To Maturity Securities $ 500,000