Material Transactions Affecting Stockholders' Equity (Details) - $ / shares				3 Months Ended
	Mar. 08, 2016	Dec. 02, 2014	May 21, 2014	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014
Class of Stock [Line Items]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01	$ 0.01				$ 0.01
Common stock, increase shares authorized (in shares)			50,000,000
Common stock and Preferred stock, shares authorized (in shares)			151,000,000
Preferred stock, shares authorized (in shares)			1,000,000	1,000,000				1,000,000
Common stock, shares authorized (in shares)			150,000,000	150,000,000				150,000,000
Common dividends declared per common share (in dollars per share)				$ 0.09	$ 0.09	$ 0.09	$ 0.09	$ 0.09	$ 0.09	$ 0.09	$ 0.09	$ 0.08	$ 0.08	$ 0.08	$ 0.07
NI Bancshares Corporation
Class of Stock [Line Items]
Common stock, shares issued (in shares)	3,042,494
Shares issued (in dollars per share)	$ 18.059
Great Lakes Financial Resources, Inc.
Class of Stock [Line Items]
Common stock, shares issued (in shares)		2,440,754
Shares issued (in dollars per share)		$ 15.737