Common Shareholder's Equity

12 Months Ended

Dec. 31, 2011

Common Shareholder's Equity [Abstract]

Common Shareholder's Equity

13.   Common Shareholders' Equity

Authorized, Reserved Common and Preferred Shares

At December 31, 2011 and 2010, the Company was authorized to issue 480.0 million shares of common stock and 20.0 million shares of preferred stock.  Of the authorized common shares, approximately 6.8 million shares at December 31, 2011 and 5.5 million shares at December 31, 2010, were reserved by the board of directors for issuance through the Company's share-based compensation plans, benefit plans, and dividend reinvestment plan.  At December 31, 2011 and 2010, there were 391.3 million and 392.8 million, respectively, of authorized shares of common stock and all authorized shares of preferred stock, available for a variety of general corporate purposes, including future public offerings to raise additional capital and for facilitating acquisitions.