Loans and Allowances for Loan Losses (Risk Rating of the Loans by Class)(Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Not Rated [Member]
Financing Receivable	$ 0	$ 0
Not Rated [Member] \| Commercial And Industrial Receivable [Member]
Financing Receivable	0	0
Not Rated [Member] \| Commercial Real Estate Other Receivable [Member]
Financing Receivable	0	0
Pass [Member]
Financing Receivable	603,370	598,623
Pass [Member] \| Commercial And Industrial Receivable [Member]
Financing Receivable	293,805	291,453
Pass [Member] \| Commercial Real Estate Other Receivable [Member]
Financing Receivable	309,565	307,170
Special Mention [Member]
Financing Receivable	30,233	15,188
Special Mention [Member] \| Commercial And Industrial Receivable [Member]
Financing Receivable	12,653	3,566
Special Mention [Member] \| Commercial Real Estate Other Receivable [Member]
Financing Receivable	17,580	11,622
Substandard [Member]
Financing Receivable	44,133	44,997
Substandard [Member] \| Commercial And Industrial Receivable [Member]
Financing Receivable	15,134	18,000
Substandard [Member] \| Commercial Real Estate Other Receivable [Member]
Financing Receivable	28,999	26,997
Doubtful [Member]
Financing Receivable	0	0
Doubtful [Member] \| Commercial And Industrial Receivable [Member]
Financing Receivable	0	0
Doubtful [Member] \| Commercial Real Estate Other Receivable [Member]
Financing Receivable	$ 0	$ 0

NATIONAL BANK OF INDIANAPOLIS CORP 10-Q