Deposits (Details 2) (USD $)	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Jul. 31, 2010
Deposits
Aggregate amounts of time deposits in denominations of $100,000 or more	$ 433,400,000	$ 464,600,000	$ 362,400,000
Insurance limit on deposit accounts before increase				100,000
Increased insurance limit on deposit accounts				250,000
Aggregate amounts of certificates of deposits in denominations of $250,000 or more	136,000,000	129,600,000	126,900,000
Traditional, out-of-market brokered deposits	$ 4,800,000	$ 13,000,000