Shareholders' Equity	12 Months Ended
Dec. 31, 2017
Shareholders' Equity [Abstract]
Shareholders' Equity	13.SHAREHOLDERS’ EQUITY Common Stock Equivalents The Company has potential common stock equivalents (see Note 14) related to its outstanding stock options and restricted stock units These potential common stock equivalents were considered in the Company’s diluted earnings per share calculation (see Note 11). Stock Repurchases On April 27, 2011, the Company’s Board of Directors authorized a stock repurchase plan. This plan authorized the Company to purchase, from time to time, up to $300.0 million of the Company’s outstanding Class A common stock through open market repurchases in compliance with Rule 10b-18 under the Exchange Act, and/or in privately negotiated transactions at management’s discretion based on market and business conditions, applicable legal requirements and other factors. During the year ended December 31, 2015, the Company repurchased 1.3 million shares of its Class A common stock at an average price of $114.96 with the remaining $150.0 million authorized under the $300.0 million stock repurchase plan, completing this plan. Shares repurchased were retired. On June 4, 2015, the Company’s Board of Directors authorized a new stock repurchase plan. This plan authorized the Company to purchase, from time to time, up to $1.0 billion of the Company’s outstanding Class A common stock through open market repurchases in compliance with Rule 10b-18 under the Exchange Act, and/or in privately negotiated transactions at management’s discretion based on market and business conditions, applicable legal requirements and other factors. During the year ended December 31, 2015, the Company repurchased an additional 2.7 million shares of its Class A common stock under this stock repurchase plan for $300.0 million at a weighted average price per share of $112.04. During the year ended December 31, 2016, the Company repurchased an additional 5.3 million shares of its Class A common stock under this stock repurchase program for $545.7 million at a weighted average price per share of $102.14. As of December 31, 2016, the Company had a remaining authorization to repurchase $154.4 million of Class A common stock under the $1.0 billion stock repurchase plan dated June 4, 2015. During the year ended December 31, 2017, the Company repurchased 42,163 shares of its Class A common stock under the stock repurchase plan dated June 4, 2015 for $4.4 million at a weighted average price per share of $104.81. Shares repurchased were retired. On January 12, 2017, the Company’s Board of Directors authorized a new stock repurchase plan, replacing the plan authorized on June 4, 2015 which had a remaining authorization of $150.0 million. This plan authorized the Company to purchase, from time to time, up to $1.0 billion of the Company’s outstanding Class A common stock through open market repurchases in compliance with Rule 10b-18 under the Exchange Act, and/or in privately negotiated transactions at management’s discretion based on market and business conditions, applicable legal requirements and other factors. During the year ended December 31, 2017, the Company repurchased 5.8 million shares of its Class A common stock under this plan for $850.0 million, at an average price per share of $146.17. Shares repurchased were retired. On February 16, 2018, the Company’s Board of Directors authorized a new $1.0 billion stock repurchase plan, replacing the prior plan authorized on January 12, 2017 which had a remaining authorization of $150.0 million. This new plan authorizes the Company to purchase, from time to time, up to $1.0 billion of our outstanding Class A common stock through open market repurchases in compliance with Rule 10b-18 under the Exchange Act and/or in privately negotiated transactions at management’s discretion based on market and business conditions, applicable legal requirements and other factors. Shares repurchased will be retired. The new plan has no time deadline and will continue until otherwise modified or terminated by the Company’s Board of Directors at any time in its sole discretion. As of the date of this filing, the Company had the full $1.0 billion authorization remaining under the new plan. Registration of Additional Shares On May 20, 2010, the Company filed a registration statement on Form S-8 with the Securities and Exchange Commission registering 15.0 million shares of the Company’s Class A common stock issuable under the 2010 Performance and Equity Incentive Plan (see Note 14). The Company filed a shelf registration statement on Form S-4 with the Securities and Exchange Commission registering 4.0 million shares of its Class A common stock in 2007. These shares may be issued in connection with acquisitions of wireless communication towers or antenna sites and related assets or companies that own wireless communication towers, antenna sites, or related assets. During the years ended December 31, 2016 and 2015, the Company did not issue any shares of its Class A common stock pursuant to this registration statement in connection with acquisitions. During the year ended December 31, 2017, the company issued 487,963 shares of Class A common stock under this registration statement. As of December 31, 2017, the Company had approximately 1.2 million shares of Class A common stock remaining under this registration statement. On March 3, 2015, the Company filed with the Commission an automatic shelf registration statement for well-known seasoned issuers on Form S-3ASR. This registration statement enables the Company to issue shares of its Class A common stock, preferred stock or debt securities either separately or represented by warrants, or depositary shares as well as units that include any of these securities. Under the rules governing automatic shelf registration statements, the Company will file a prospectus supplement and advise the Commission of the amount and type of securities each time it issues securities under this registration statement. For the years ended December 31, 2017, 2016, and 2015, the Company did not issue any securities under this automatic shelf registration statement.

13.SHAREHOLDERS’ EQUITY

Common Stock Equivalents

The Company has potential common stock equivalents (see Note 14) related to its outstanding stock options and restricted stock units These potential common stock equivalents were considered in the Company’s diluted earnings per share calculation (see Note 11).

Stock Repurchases

On April 27, 2011, the Company’s Board of Directors authorized a stock repurchase plan. This plan authorized the Company to purchase, from time to time, up to $300.0 million of the Company’s outstanding Class A common stock through open market repurchases in compliance with Rule 10b-18 under the Exchange Act, and/or in privately negotiated transactions at management’s discretion based on market and business conditions, applicable legal requirements and other factors. During the year ended December 31, 2015, the Company repurchased 1.3 million shares of its Class A common stock at an average price of $114.96 with the remaining $150.0 million authorized under the $300.0 million stock repurchase plan, completing this plan. Shares repurchased were retired.

On June 4, 2015, the Company’s Board of Directors authorized a new stock repurchase plan. This plan authorized the Company to purchase, from time to time, up to $1.0 billion of the Company’s outstanding Class A common stock through open market repurchases in compliance with Rule 10b-18 under the Exchange Act, and/or in privately negotiated transactions at management’s discretion based on market and business conditions, applicable legal requirements and other factors. During the year ended December 31, 2015, the Company repurchased an additional 2.7 million shares of its Class A common stock under this stock repurchase plan for $300.0 million at a weighted average price per share of $112.04. During the year ended December 31, 2016, the Company repurchased an additional 5.3 million shares of its Class A common stock under this stock repurchase program for $545.7 million at a weighted average price per share of $102.14. As of December 31, 2016, the Company had a remaining authorization to repurchase $154.4 million of Class A common stock under the $1.0 billion stock repurchase plan dated June 4, 2015. During the year ended December 31, 2017, the Company repurchased 42,163 shares of its Class A common stock under the stock repurchase plan dated June 4, 2015 for $4.4 million at a weighted average price per share of $104.81. Shares repurchased were retired.

On January 12, 2017, the Company’s Board of Directors authorized a new stock repurchase plan, replacing the plan authorized on June 4, 2015 which had a remaining authorization of $150.0 million. This plan authorized the Company to purchase, from time to time, up to $1.0 billion of the Company’s outstanding Class A common stock through open market repurchases in compliance with Rule 10b-18 under the Exchange Act, and/or in privately negotiated transactions at management’s discretion based on market and business conditions, applicable legal requirements and other factors. During the year ended December 31, 2017, the Company repurchased 5.8 million shares of its Class A common stock under this plan for $850.0 million, at an average price per share of $146.17. Shares repurchased were retired.

On February 16, 2018, the Company’s Board of Directors authorized a new $1.0 billion stock repurchase plan, replacing the prior plan authorized on January 12, 2017 which had a remaining authorization of $150.0 million. This new plan authorizes the Company to purchase, from time to time, up to $1.0 billion of our outstanding Class A common stock through open market repurchases in compliance with Rule 10b-18 under the Exchange Act and/or in privately negotiated transactions at management’s discretion based on market and business conditions, applicable legal requirements and other factors. Shares repurchased will be retired. The new plan has no time deadline and will continue until otherwise modified or terminated by the Company’s Board of Directors at any time in its sole discretion. As of the date of this filing, the Company had the full $1.0 billion authorization remaining under the new plan.

Registration of Additional Shares

On May 20, 2010, the Company filed a registration statement on Form S-8 with the Securities and Exchange Commission registering 15.0 million shares of the Company’s Class A common stock issuable under the 2010 Performance and Equity Incentive Plan (see Note 14).

The Company filed a shelf registration statement on Form S-4 with the Securities and Exchange Commission registering 4.0 million shares of its Class A common stock in 2007. These shares may be issued in connection with acquisitions of wireless communication towers or antenna sites and related assets or companies that own wireless communication towers, antenna sites, or related assets. During the years ended December 31, 2016 and 2015, the Company did not issue any shares of its Class A common stock pursuant to this registration statement in connection with acquisitions. During the year ended December 31, 2017, the company issued 487,963 shares of Class A common stock under this registration statement. As of December 31, 2017, the Company had approximately 1.2 million shares of Class A common stock remaining under this registration statement.

On March 3, 2015, the Company filed with the Commission an automatic shelf registration statement for well-known seasoned issuers on Form S-3ASR. This registration statement enables the Company to issue shares of its Class A common stock, preferred stock or debt securities either separately or represented by warrants, or depositary shares as well as units that include any of these securities. Under the rules governing automatic shelf registration statements, the Company will file a prospectus supplement and advise the Commission of the amount and type of securities each time it issues securities under this registration statement. For the years ended December 31, 2017, 2016, and 2015, the Company did not issue any securities under this automatic shelf registration statement.