Shareholders' Equity - Summary of Share Count and Par Value Data Related to Shareholders' Equity (Details) - $ / shares	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Preferred Stock
Par value per share	$ 0	$ 0
Shares authorized, shares	25,000,000	25,000,000
Shares outstanding, shares	0	0
Common Stock
Par value per share	$ 0	$ 0
Shares authorized, shares	75,000,000	75,000,000
Shares issued, shares	56,242,499	56,101,700
Shares outstanding	32,548,477	33,392,060	33,558,864
Treasury stock
Shares held, shares	23,694,022	22,709,640