Business Combinations (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011	Mar. 31, 2011 Midwest Bank and Trust Company [Member]
ASSETS
Goodwill	$ 460,044	$ 460,044	$ 460,044	$ 460,044	$ 272,100

Carrying amount as of the balance sheet date, which is the cumulative amount paid and (if applicable) the fair value of any noncontrolling interest in the acquiree, adjusted for any amortization recognized prior to the adoption of any changes in generally accepted accounting principles (as applicable) and for any impairment charges, in excess of the fair value of net assets acquired in one or more business combination transactions.

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+ Details