Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Condensed Consolidated Statement of Changes in Stockholders’ Equity
Issuance of common stock for employee stock option plan		39,002	14,228
Issuance of common stock for director stock option exercises, shares	24,498
Issuance of common stock for restricted share awards, shares	1,133,183	1,159,047	1,123,720
Net excess tax benefit	$ 0.2	$ 2.1	$ 0.6
Issuance of common stock for the employee stock purchase plan, shares	95,981	70,924	71,587
Shares repurchased to satisfy minimum statutory withholding tax upon the net settlement of equity awards	391,195	418,135	367,367
Purchase of common stock for treasury, shares	1,336,132	1,992,831	2,671,637