Acquisition (Details 2) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Amounts of loans
Outstanding balance	$ 1,117,666	$ 1,190,717
Carrying amount, net of allowance of $404	1,097,362	1,170,196
Heartland Bancshares Inc [Member]
Amounts of loans
Outstanding balance	79,811
Carrying amount, net of allowance of $404	79,407
Commercial [Member] | Heartland Bancshares Inc [Member]
Amounts of loans
Outstanding balance	52,469
Real estate [Member] | Heartland Bancshares Inc [Member]
Amounts of loans
Outstanding balance	13,848
Consumer [Member] | Heartland Bancshares Inc [Member]
Amounts of loans
Outstanding balance	$ 13,494