Income Taxes - Additional Information (Detail)	3 Months Ended
Mar. 31, 2016
Income Tax Disclosure [Abstract]
Income tax examination description	During the three months ended March 31, 2016, the Illinois Department of Revenue completed an audit, subject to quality review, of the Company’s corporate income tax returns for the tax years ended December 31, 2013 and 2012 and proposed no changes. The Company does not expect any additional tax liabilities, penalties and/or interest as a result of the audit.

A brief description of status of the tax examination, significant findings to date, and the entity's position with respect to the findings.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (d)(2)
-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32718-109319

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