Common Stock Repurchase Program	9 Months Ended
Sep. 30, 2016
Notes To Financial Statements [Abstract]
Common Stock Repurchase	Common Stock Repurchase April 2014 Repurchase Program In April 2014, we announced that our Board of Directors had authorized a stock repurchase program ("April 2014 Repurchase Program") pursuant to which we may purchase up to $300.0 million of our common stock over the next three years. On May 3, 2016, as part of our $300.0 million April 2014 Repurchase Program, we entered into an accelerated share repurchase agreement ("ASR") to repurchase $50.0 million of our common stock (the "2016 ASR".) Under the terms of the 2016 ASR, we paid $50.0 million and received an initial delivery of approximately 0.5 million shares. The 2016 ASR was completed on September 6, 2016 with a final delivery of approximately 0.1 million shares. We received a total of approximately 0.6 million shares under the 2016 ASR at a weighted average share price of $81.89. The final number of shares repurchased was based on our volume-weighted average stock price during the term of the transaction, less an agreed upon discount. During 2016, we have repurchased on the open market approximately 0.1 million shares of our common stock at a weighted average of $93.21 per share, including commissions, for an aggregate purchase price of approximately $8.2 million. All repurchased shares were retired. As of September 30, 2016, we have $41.8 million remaining under the April 2014 Repurchase Program. April 2016 Repurchase Program On April 28, 2016, we announced that our Board of Directors had authorized an additional plan to repurchase up to $300.0 million of the Company's stock ("the April 2016 Repurchase Plan"). Any purchases under this stock repurchase program may be made, from time-to-time, pursuant to open market purchases (including pursuant to Rule 10b5-1 plans), privately-negotiated transactions, accelerated stock repurchases, block trades or derivative contracts or otherwise in accordance with applicable federal securities laws, including Rule 10b-18 of the Securities Exchange Act of 1934. As of September 30, 2016, there have not been any repurchases under this plan.

Common Stock Repurchase

April 2014 Repurchase Program

In April 2014, we announced that our Board of Directors had authorized a stock repurchase program ("April 2014 Repurchase Program") pursuant to which we may purchase up to $300.0 million of our common stock over the next three years.

On May 3, 2016, as part of our $300.0 million April 2014 Repurchase Program, we entered into an accelerated share repurchase agreement ("ASR") to repurchase $50.0 million of our common stock (the "2016 ASR".) Under the terms of the 2016 ASR, we paid $50.0 million and received an initial delivery of approximately 0.5 million shares. The 2016 ASR was completed on September 6, 2016 with a final delivery of approximately 0.1 million shares. We received a total of approximately 0.6 million shares under the 2016 ASR at a weighted average share price of $81.89. The final number of shares repurchased was based on our volume-weighted average stock price during the term of the transaction, less an agreed upon discount.

During 2016, we have repurchased on the open market approximately 0.1 million shares of our common stock at a weighted average of $93.21 per share, including commissions, for an aggregate purchase price of approximately $8.2 million. All repurchased shares were retired. As of September 30, 2016, we have $41.8 million remaining under the April 2014 Repurchase Program.

April 2016 Repurchase Program

On April 28, 2016, we announced that our Board of Directors had authorized an additional plan to repurchase up to $300.0 million of the Company's stock ("the April 2016 Repurchase Plan"). Any purchases under this stock repurchase program may be made, from time-to-time, pursuant to open market purchases (including pursuant to Rule 10b5-1 plans), privately-negotiated transactions, accelerated stock repurchases, block trades or derivative contracts or otherwise in accordance with applicable federal securities laws, including Rule 10b-18 of the Securities Exchange Act of 1934. As of September 30, 2016, there have not been any repurchases under this plan.