Convertible Senior Notes - Additional Information (Detail) | 1 Months Ended | 3 Months Ended | 6 Months Ended | | |
Jun. 30, 2018USD ($)dDerivative$ / shares$ / Derivativeshares | Jun. 30, 2015USD ($)dDerivative$ / shares$ / Derivativeshares | Jun. 30, 2014USD ($)dDerivative$ / shares$ / Derivativeshares | Aug. 04, 2018USD ($)$ / shares | Jul. 29, 2017USD ($) | Aug. 04, 2018USD ($)$ / shares | Jul. 29, 2017USD ($) | Feb. 03, 2018USD ($) | Jul. 31, 2015USD ($) |
Debt Instrument [Line Items] | | | | | | | | | |
Amortization of debt discount | | | | | | $ 17,645,000 | $ 15,018,000 | | |
Total cost of convertible note hedge transactions | | | | | | 91,857,000 | | | |
Cash proceeds from sale of warrants | | | | | | 51,021,000 | | | |
Convertible Senior Notes Due 2023 [Member] | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | |
Debt instrument, principal amount | | | | $ 335,000,000 | | 335,000,000 | | | |
Deemed elected combination settlement amount per note to be received upon conversion | $ 1,000 | | | | | | | | |
Debt instrument, effective interest rate | 6.35% | | | | | | | | |
Discounts and commissions payable | $ 1,700,000 | | | 89,217,000 | | 89,217,000 | | | |
Third party offering costs | $ 4,600,000 | | | | | | | | |
Amortization of debt issuance costs | | | | 100,000 | | 100,000 | | | |
Amortization of debt discount | | | | 1,800,000 | | $ 1,800,000 | | | |
Warrants sold to purchase common stock | shares | 1,700,000 | | | | | | | | |
Cash proceeds from sale of warrants | $ 51,000,000 | | | | | | | | |
Warrants price per share | $ / shares | $ 309.84 | | | | | | | | |
Convertible Senior Notes Due 2023 [Member] | Convertible Bond Hedge and Warrant Transactions [Member] | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | |
Conversion price per share | $ / shares | $ 309.84 | | | | | | | | |
Convertible note hedge, number of shares | Derivative | 1,700,000 | | | | | | | | |
Convertible note hedge, price per share | $ / Derivative | 193.65 | | | | | | | | |
Convertible note hedge, description | | | | | | The Company entered into convertible note hedge transactions whereby the Company has the option to purchase a total of approximately 1.7 million shares of its common stock at a price of approximately $193.65 per share. | | | |
Convertible note hedge, inception Date | | | | | | Jun. 30, 2018 | | | |
Total cost of convertible note hedge transactions | $ 91,900,000 | | | | | | | | |
Deferred tax liability | | | | 22,300,000 | | $ 22,300,000 | | | |
Deferred tax asset | | | | $ 22,500,000 | | $ 22,500,000 | | | |
Convertible Senior Notes Due 2023 [Member] | Convertible Bond Hedge and Warrant Transactions [Member] | Warrants Subject to Certain Adjustment Mechanisms [Member] | Maximum [Member] | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | |
Warrants sold to purchase common stock | shares | 3,500,000 | | | | | | | | |
Convertible Senior Notes Due 2023 [Member] | Convertible Debt Instrument Conversion Period One [Member] | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | |
Debt instrument, convertible trading days | d | 20 | | | | | | | | |
Debt instrument, convertible consecutive trading days | d | 30 | | | | | | | | |
Debt instrument, convertible percentage of stock price | 130.00% | | | | | | | | |
Convertible Senior Notes Due 2023 [Member] | Convertible Debt Instrument Conversion Period Two [Member] | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | |
Debt instrument, convertible trading days | d | 5 | | | | | | | | |
Debt instrument, convertible consecutive trading days | d | 10 | | | | | | | | |
Debt instrument, convertible percentage of stock price | 98.00% | | | | | | | | |
Convertible Senior Notes Due 2023 [Member] | Convertible Debt Instrument Conversion Period Three [Member] | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | |
Debt instrument, convertible earliest date | | | | | | Mar. 15, 2023 | | | |
Convertible Senior Notes Due 2023 [Member] | Common Stock [Member] | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | |
Debt instrument, initial conversion rate | 5.1640 | | | | | | | | |
Debt instrument, conversion principal amount | $ 1,000 | | | | | | | | |
Conversion price per share | $ / shares | $ 193.65 | | | $ 193.65 | | $ 193.65 | | | |
Debt instrument, conversion description | | | | | | The initial conversion rate applicable to the 2023 Notes is 5.1640 shares of common stock per $1,000 principal amount of 2023 Notes, which is equivalent to an initial conversion price of approximately $193.65 per share. | | | |
Convertible Senior Notes Due 2020 [Member] | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | |
Debt instrument, principal amount | | | | $ 300,000,000 | | $ 300,000,000 | | $ 300,000,000 | |
Deemed elected combination settlement amount per note to be received upon conversion | | $ 1,000 | | | | | | | |
Debt instrument, effective interest rate | | 6.47% | | | | | | | |
Discounts and commissions payable | | $ 3,800,000 | | 35,745,000 | | 35,745,000 | | 44,135,000 | |
Third party offering costs | | $ 2,300,000 | | | | | | | |
Amortization of debt issuance costs | | | | 300,000 | $ 300,000 | 500,000 | 500,000 | | |
Amortization of debt discount | | | | 4,200,000 | 4,000,000 | $ 8,400,000 | 7,900,000 | | |
Warrants sold to purchase common stock | shares | | 2,500,000 | | | | | | | |
Cash proceeds from sale of warrants | | $ 30,400,000 | | | | | | | |
Warrants price per share | $ / shares | | $ 189 | | | | | | | |
Convertible Senior Notes Due 2020 [Member] | Convertible Bond Hedge and Warrant Transactions [Member] | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | |
Conversion price per share | $ / shares | | $ 189 | | | | | | | |
Convertible note hedge, number of shares | Derivative | | 2,500,000 | | | | | | | |
Convertible note hedge, price per share | $ / Derivative | | 118.13 | | | | | | | |
Convertible note hedge, description | | | | | | The Company entered into convertible note hedge transactions whereby the Company has the option to purchase a total of approximately 2.5 million shares of its common stock at a price of approximately $118.13 per share | | | |
Convertible note hedge, inception Date | | | | | | Jun. 30, 2015 | | | |
Total cost of convertible note hedge transactions | | $ 68,300,000 | | | | | | | |
Deferred tax liability | | | | 32,800,000 | | $ 32,800,000 | | | |
Deferred tax asset | | | | $ 26,600,000 | | $ 26,600,000 | | | |
Convertible Senior Notes Due 2020 [Member] | Convertible Bond Hedge and Warrant Transactions [Member] | Warrants Subject to Certain Adjustment Mechanisms [Member] | Maximum [Member] | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | |
Warrants sold to purchase common stock | shares | | 5,100,000 | | | | | | | |
Convertible Senior Notes Due 2020 [Member] | Convertible Debt Instrument Conversion Period One [Member] | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | |
Debt instrument, convertible trading days | d | | 20 | | | | | | | |
Debt instrument, convertible consecutive trading days | d | | 30 | | | | | | | |
Debt instrument, convertible percentage of stock price | | 130.00% | | | | | | | |
Convertible Senior Notes Due 2020 [Member] | Convertible Debt Instrument Conversion Period Two [Member] | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | |
Debt instrument, convertible trading days | d | | 5 | | | | | | | |
Debt instrument, convertible consecutive trading days | d | | 10 | | | | | | | |
Debt instrument, convertible percentage of stock price | | 98.00% | | | | | | | |
Convertible Senior Notes Due 2020 [Member] | Convertible Debt Instrument Conversion Period Three [Member] | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | |
Debt instrument, convertible earliest date | | | | | | Mar. 15, 2020 | | | |
Convertible Senior Notes Due 2020 [Member] | Common Stock [Member] | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | |
Debt instrument, initial conversion rate | | 8.4656 | | | | | | | |
Debt instrument, conversion principal amount | | $ 1,000 | | | | | | | |
Conversion price per share | $ / shares | | $ 118.13 | | $ 118.13 | | $ 118.13 | | | |
Debt instrument, conversion description | | | | | | The initial conversion rate applicable to the 2020 Notes is 8.4656 shares of common stock per $1,000 principal amount of 2020 Notes, which is equivalent to an initial conversion price of approximately $118.13 per share. | | | |
Convertible Senior Notes Due 2019 [Member] | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | |
Debt instrument, principal amount | | | | $ 350,000,000 | | $ 350,000,000 | | 350,000,000 | |
Debt instrument, convertible earliest date | | | | | | Mar. 15, 2019 | | | |
Deemed elected combination settlement amount per note to be received upon conversion | | | $ 1,000 | | | | | | |
Debt instrument, effective interest rate | | | 4.51% | | | | | | |
Discounts and commissions payable | | | $ 4,400,000 | 13,506,000 | | $ 13,506,000 | | $ 20,988,000 | |
Third party offering costs | | | $ 1,000,000 | | | | | | |
Amortization of debt issuance costs | | | | 300,000 | 200,000 | 500,000 | 400,000 | | |
Amortization of debt discount | | | | 3,800,000 | $ 3,600,000 | $ 7,500,000 | $ 7,200,000 | | |
Warrants sold to purchase common stock | shares | | | 3,000,000 | | | | | | |
Cash proceeds from sale of warrants | | | $ 40,400,000 | | | | | | |
Warrants price per share | $ / shares | | | $ 171.98 | | | | | | |
Convertible Senior Notes Due 2019 [Member] | Convertible Bond Hedge and Warrant Transactions [Member] | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | |
Convertible note hedge, number of shares | Derivative | | | 3,000,000 | | | | | | |
Convertible note hedge, price per share | $ / Derivative | | | 116.09 | | | | | | |
Convertible note hedge, description | | | | | | the Company entered into convertible note hedge transactions whereby the Company has the option to purchase a total of approximately 3.0 million shares of its common stock at a price of approximately $116.09 per share. | | | |
Total cost of convertible note hedge transactions | | | $ 73,300,000 | | | | | | |
Deferred tax liability | | | | 27,500,000 | | $ 27,500,000 | | | |
Deferred tax asset | | | | $ 28,600,000 | | $ 28,600,000 | | | |
Conversion price per share, two | $ / shares | | | $ 171.98 | | | | | | |
Convertible Senior Notes Due 2019 [Member] | Convertible Bond Hedge and Warrant Transactions [Member] | Warrants Subject to Certain Adjustment Mechanisms [Member] | Maximum [Member] | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | |
Warrants sold to purchase common stock | shares | | | 6,000,000 | | | | | | |
Convertible Senior Notes Due 2019 [Member] | Convertible Debt Instrument Conversion Period One [Member] | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | |
Debt instrument, convertible trading days | d | | | 20 | | | | | | |
Debt instrument, convertible consecutive trading days | d | | | 30 | | | | | | |
Debt instrument, convertible percentage of stock price | | | 130.00% | | | | | | |
Convertible Senior Notes Due 2019 [Member] | Convertible Debt Instrument Conversion Period Two [Member] | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | |
Debt instrument, convertible trading days | d | | | 5 | | | | | | |
Debt instrument, convertible consecutive trading days | d | | | 10 | | | | | | |
Debt instrument, convertible percentage of stock price | | | 98.00% | | | | | | |
Convertible Senior Notes Due 2019 [Member] | Convertible Debt Instrument Conversion Period Three [Member] | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | |
Debt instrument, convertible earliest date | | | | | | Mar. 15, 2019 | | | |
Convertible Senior Notes Due 2019 [Member] | Common Stock [Member] | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | |
Debt instrument, initial conversion rate | | | 8.6143 | | | | | | |
Debt instrument, conversion principal amount | | | $ 1,000 | | | | | | |
Conversion price per share | $ / shares | | | $ 116.09 | $ 116.09 | | $ 116.09 | | | |
Debt instrument, conversion description | | | | | | The initial conversion rate applicable to the 2019 Notes is 8.6143 shares of common stock per $1,000 principal amount of 2019 Notes, which is equivalent to an initial conversion price of approximately $116.09 per share | | | |
Private Placement [Member] | Convertible Senior Notes Due 2023 [Member] | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | |
Debt instrument, principal amount | $ 300,000,000 | | | | | | | | |
Debt instrument, interest rate | 0.00% | | | | | | | | |
Debt instrument, maturity date | | | | | | Jun. 15, 2023 | | | |
Private Placement [Member] | Convertible Senior Notes Due 2020 [Member] | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | |
Debt instrument, principal amount | | $ 250,000,000 | | | | | | | |
Debt instrument, interest rate | | 0.00% | | | | | | | |
Debt instrument, maturity date | | | | | | Jul. 15, 2020 | | | |
Private Placement [Member] | Convertible Senior Notes Due 2019 [Member] | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | |
Debt instrument, principal amount | | | $ 350,000,000 | | | | | | |
Debt instrument, interest rate | | | 0.00% | | | | | | |
Debt instrument, maturity date | | | | | | Jun. 15, 2019 | | | |
Over Allotment Option in Private Placement [Member] | Convertible Senior Notes Due 2023 [Member] | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | |
Debt instrument, principal amount | $ 35,000,000 | | | | | | | | |
Exercise of Over Allotment Option in Private Placement [Member] | Convertible Senior Notes Due 2020 [Member] | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | |
Debt instrument, principal amount | | | | | | | | | $ 50,000,000 |