Capital Stock	6 Months Ended
Jun. 30, 2018
Equity [Abstract]
Capital Stock	Capital Stock Treasury Stock In February 2018, the Board of Directors authorized an increase of 25.0 million shares to the Company’s share repurchase program. After this authorization, the total number of shares available for repurchase was 30.1 million shares. Under the share repurchase program, the Company may purchase shares of common stock in the open market or in negotiated transactions. The timing and amount of any stock purchases are determined at the discretion of management. The Company may use the repurchased shares to fund stock compensation programs currently in existence, or for other corporate purposes. All purchases executed to date have been through open market transactions. There is no expiration date associated with the authorization to repurchase common stock of the Company. During the first six months of 2018, the Company repurchased 20.0 million shares for a total cost of $481.5 million. As of June 30, 2018, 10.1 million shares are available for repurchase under the share repurchase program. No treasury shares have been delivered or sold by the Company subsequent to the repurchase. As of June 30, 2018, 34.9 million shares were held as treasury stock, which includes 2.6 million shares that were repurchased prior to June 30, 2018 and settled in July 2018. Subsequent Event. In July 2018, the Board of Directors authorized an increase of 20.0 million shares to the Company’s share repurchase program. After this authorization, the total number of shares available for repurchase is 30.1 million shares.

Capital Stock

Treasury Stock

In February 2018, the Board of Directors authorized an increase of 25.0 million shares to the Company’s share repurchase program. After this authorization, the total number of shares available for repurchase was 30.1 million shares. Under the share repurchase program, the Company may purchase shares of common stock in the open market or in negotiated transactions. The timing and amount of any stock purchases are determined at the discretion of management. The Company may use the repurchased shares to fund stock compensation programs currently in existence, or for other corporate purposes. All purchases executed to date have been through open market transactions. There is no expiration date associated with the authorization to repurchase common stock of the Company.

During the first six months of 2018, the Company repurchased 20.0 million shares for a total cost of $481.5 million. As of June 30, 2018, 10.1 million shares are available for repurchase under the share repurchase program.

No treasury shares have been delivered or sold by the Company subsequent to the repurchase. As of June 30, 2018, 34.9 million shares were held as treasury stock, which includes 2.6 million shares that were repurchased prior to June 30, 2018 and settled in July 2018.

Subsequent Event. In July 2018, the Board of Directors authorized an increase of 20.0 million shares to the Company’s share repurchase program. After this authorization, the total number of shares available for repurchase is 30.1 million shares.