Shareholders' Equity (Tables)

12 Months Ended

Dec. 31, 2017

Stockholders' Equity Note [Abstract]

Summary of Share Count and Par Value Data Related to Shareholders' Equity

Share count and par value data related to shareholders' equity are as follows:

	As of December 31,
	2017	2016
Preferred Stock
Par value per share	No par value	No par value
Shares authorized	25,000,000	25,000,000
Shares outstanding	—	—
Common Stock
Par value per share	No par value	No par value
Shares authorized	75,000,000	75,000,000
Shares issued	56,632,488	56,456,516
Shares outstanding	32,938,466	32,762,494
Treasury stock
Shares held	23,694,022	23,694,022

Summary of Common Shares Outstanding

A roll forward of common shares outstanding is as follows:

	As of December 31,
	2017	2016
Balance at beginning of the year	32,762,494	32,548,477
Restricted stock unit issuances	175,972	214,017
Balance at end of period	32,938,466	32,762,494