Common Stock	6 Months Ended
Jun. 30, 2018
Equity [Abstract]
Common Stock	Common Stock Share Repurchase Program In June 2018, the Company entered into an accelerated share repurchase ("ASR") agreement with a third-party financial institution to repurchase the Company's common stock. Under the ASR agreement, the Company made an up-front payment of $35,000 and received an initial delivery of 207,193 shares in the second quarter of 2018. The total number of shares to be ultimately delivered, and therefore the average price paid per share, will be determined at the end of the repurchase period based on the volume weighted average price of the Company's common stock during that period. The ASR is expected to be completed no later than the fourth quarter of 2018. In addition to the repurchase under the ASR agreement, during the six months ended June 30, 2018, the Company repurchased 69,503 shares of its common stock at an average purchase price of $122.64 per share, excluding commissions, for a total cost of $8,524. During the six months ended June 30, 2017, the Company repurchased 92,409 shares at an average purchase price of $100.85 per share, excluding commissions, for a total cost of $9,319, of which $7,514 was settled in cash during the quarter. Also in June 2018, the Company’s Board of Directors approved a new common stock repurchase program (the “2018 Program”) authorizing the Company to repurchase, in the aggregate, up to $150,000 of its outstanding common stock. Under the 2018 Program, repurchases may be made on the open market, through private transactions, accelerated share repurchases, round lot or block transactions on the New York Stock Exchange or otherwise, as determined by the Company’s management and in accordance with prevailing market conditions and federal securities laws and regulations. The 2018 Program, which is effective in November 2018, replaces the prior $125,000 authorization to repurchase shares approved by the board in March 2016 (the “2016 Program”). As of June 30, 2018, the Company had approximately $1,700 of repurchase authorization remaining under the 2016 Program.

Common Stock

Share Repurchase Program

In June 2018, the Company entered into an accelerated share repurchase ("ASR") agreement with a third-party financial institution to repurchase the Company's common stock. Under the ASR agreement, the Company made an up-front payment of $35,000 and received an initial delivery of 207,193 shares in the second quarter of 2018. The total number of shares to be ultimately delivered, and therefore the average price paid per share, will be determined at the end of the repurchase period based on the volume weighted average price of the Company's common stock during that period. The ASR is expected to be completed no later than the fourth quarter of 2018.

In addition to the repurchase under the ASR agreement, during the six months ended June 30, 2018, the Company repurchased 69,503 shares of its common stock at an average purchase price of $122.64 per share, excluding commissions, for a total cost of $8,524. During the six months ended June 30, 2017, the Company repurchased 92,409 shares at an average purchase price of $100.85 per share, excluding commissions, for a total cost of $9,319, of which $7,514 was settled in cash during the quarter.

Also in June 2018, the Company’s Board of Directors approved a new common stock repurchase program (the “2018 Program”) authorizing the Company to repurchase, in the aggregate, up to $150,000 of its outstanding common stock. Under the 2018 Program, repurchases may be made on the open market, through private transactions, accelerated share repurchases, round lot or block transactions on the New York Stock Exchange or otherwise, as determined by the Company’s management and in accordance with prevailing market conditions and federal securities laws and regulations. The 2018 Program, which is effective in November 2018, replaces the prior $125,000 authorization to repurchase shares approved by the board in March 2016 (the “2016 Program”). As of June 30, 2018, the Company had approximately $1,700 of repurchase authorization remaining under the 2016 Program.