Capital Stock	3 Months Ended
Mar. 31, 2018
Class of Stock Disclosures [Abstract]
Capital Stock	Note 10. Capital Stock Class A and B common stock Holders of Class B shares may, at their option, convert their shares into Class A shares at the rate of 2,400 Class A shares per Class B share. There were no shares of Class B common stock converted into Class A common stock during the three months ended March 31, 2018 and the year ended December 31, 2017. There is no provision for conversion of Class A shares to Class B shares, and Class B shares surrendered for conversion cannot be reissued. Stock repurchases In 2011, our Board of Directors approved a continuation of the current stock repurchase program of $150 million, with no time limitation. There were no shares repurchased under this program during the three months ended March 31, 2018 and the year ended December 31, 2017. We had approximately $17.8 million of repurchase authority remaining under this program at March 31, 2018. During the three months ended March 31, 2018, we purchased 17,291 shares of our outstanding Class A nonvoting common stock outside of our publicly announced share repurchase program at a total cost of $2.1 million. Of this amount, we purchased 3,250 shares for $0.4 million, or $119.83 per share, for stock-based awards in conjunction with our equity compensation plan. We purchased 2,284 shares for $0.3 million, or $114.87 per share, to fund the rabbi trust for the outside director deferred stock compensation plan. The remaining 11,757 shares were purchased at a total cost of $1.4 million, or $119.17 per share, to fund the rabbi trust for the incentive compensation deferral plan. The shares were transferred to the rabbi trust in March 2018. During the year ended December 31, 2017, we purchased 60,332 shares of our outstanding Class A nonvoting common stock outside of our publicly announced share repurchase program at a total cost of $7.3 million. Of this amount, we purchased 3,785 shares for $0.4 million, or $111.55 per share, for stock-based awards in conjunction with our equity compensation plan. We purchased 9,663 shares for $1.2 million, or $121.85 per share, to fund the rabbi trust for the outside director deferred stock compensation plan. The remaining 46,884 shares were purchased at a total cost of $5.7 million, or $122.40 per share, for the vesting of stock-based awards in conjunction with our long-term incentive plan. These shares were delivered in 2017.

Note 10. Capital Stock

Class A and B common stock

Holders of Class B shares may, at their option, convert their shares into Class A shares at the rate of 2,400 Class A shares per Class B share. There were no shares of Class B common stock converted into Class A common stock during the three months ended March 31, 2018 and the year ended December 31, 2017. There is no provision for conversion of Class A shares to Class B shares, and Class B shares surrendered for conversion cannot be reissued.

Stock repurchases

In 2011, our Board of Directors approved a continuation of the current stock repurchase program of $150 million, with no time limitation. There were no shares repurchased under this program during the three months ended March 31, 2018 and the year ended December 31, 2017. We had approximately $17.8 million of repurchase authority remaining under this program at March 31, 2018.

During the three months ended March 31, 2018, we purchased 17,291 shares of our outstanding Class A nonvoting common stock outside of our publicly announced share repurchase program at a total cost of $2.1 million. Of this amount, we purchased 3,250 shares for $0.4 million, or $119.83 per share, for stock-based awards in conjunction with our equity compensation plan. We purchased 2,284 shares for $0.3 million, or $114.87 per share, to fund the rabbi trust for the outside director deferred stock compensation plan. The remaining 11,757 shares were purchased at a total cost of $1.4 million, or $119.17 per share, to fund the rabbi trust for the incentive compensation deferral plan. The shares were transferred to the rabbi trust in March 2018.

During the year ended December 31, 2017, we purchased 60,332 shares of our outstanding Class A nonvoting common stock outside of our publicly announced share repurchase program at a total cost of $7.3 million. Of this amount, we purchased 3,785 shares for $0.4 million, or $111.55 per share, for stock-based awards in conjunction with our equity compensation plan. We purchased 9,663 shares for $1.2 million, or $121.85 per share, to fund the rabbi trust for the outside director deferred stock compensation plan. The remaining 46,884 shares were purchased at a total cost of $5.7 million, or $122.40 per share, for the vesting of stock-based awards in conjunction with our long-term incentive plan. These shares were delivered in 2017.