Long-Term Debt	12 Months Ended
Dec. 31, 2013
Debt Disclosure [Abstract]
Long-Term Debt	Long-term Debt Senior Convertible Notes In November 2011, the Company issued $200.0 million aggregate principal amount of zero coupon senior convertible notes due on December 1, 2018 (the “Convertible Notes”) in a private placement offering to TCV VII, L.P., TCV VII(A), L.P., and TCV Member Fund, L.P. A general partner of these funds also serves on the Company’s Board of Directors, and as such, the issuance of the notes is considered a related party transaction. The net proceeds to the Company were approximately $197.8 million. Debt issuance costs of $2.2 million (of which $0.3 million was paid in the year ended December 31, 2012) were recorded in “Other non-current assets” on the Consolidated Balance Sheets and were amortized over the term of the notes as interest expense. At any time following May 28, 2012, the Company could have elected to cause the conversion of the Convertible Notes into shares of the Company’s common stock when specified conditions were satisfied, including that the daily volume weighted average price of the Company’s common stock was equal to or greater than $111.54 for at least 50 trading days during a 65 trading day period prior to the conversion date. The Company determined that the embedded conversion option in the Convertible Notes did not require separate accounting treatment as a derivative instrument because it was both indexed to the Company's own stock and would be classified in stockholders' equity if freestanding. Additionally, the Convertible Notes did not require or permit any portion of the obligation to be settled in cash and accordingly the liability and equity (conversion option) components were not required to be accounted for separately. In April 2013, after all specified conditions were satisfied, the Company elected to cause the conversion of all outstanding Convertible Notes with an aggregate principal amount of $200.0 million in accordance with the terms of the Indenture governing such notes. Pursuant to this conversion, the Company issued 2.3 million shares of common stock to the holders of the Convertible Notes at a conversion ratio of 11.6553. The fair market value of one share of common stock on the date of conversion was $216.99 per share. Senior Notes In November 2009, the Company issued $200.0 million aggregate principal amount of 8.50% senior notes due November 15, 2017 (the “8.50% Notes”). The net proceeds to the Company were approximately $193.9 million. Debt issuance costs of $6.1 million were recorded in “Other non-current assets” on the Consolidated Balance Sheets and were amortized over the term of the notes as interest expense. The notes were issued at par and were senior unsecured obligations of the Company. Interest was payable semi-annually at a rate of 8.50% per annum on May 15 and November 15 of each year, commencing on May 15, 2010. The 8.50% Notes were repayable in whole or in part upon the occurrence of a change of control, at the option of the holders, at a purchase price in cash equal to 101% of the principal plus accrued interest. The Company could redeem the 8.50% Notes prior to November 15, 2013 in whole or in part at a redemption price of 100% of the principal plus accrued interest, plus a “make-whole” premium. In February 2013, the Company issued $500.0 million aggregate principal amount of 5.375% senior notes due 2021 (the “5.375% Notes”). The 5.375% Notes were issued at par and are senior unsecured obligations of the Company. Interest is payable semi-annually at a rate of 5.375% per annum on February 1 and August 1 of each year, commencing on August 1, 2013. The 5.375% Notes are repayable in whole or in part upon the occurrence of a change of control, at the option of the holders, at a purchase price in cash equal to 101% of the principal plus accrued interest. The Company may redeem the 5.375% Notes prior to maturity in whole or in part at an amount equal to the principal amount thereof plus accrued and unpaid interest plus a make-whole payment equivalent to the present value of the remaining interest payments through maturity. The 5.375% Notes include, among other terms and conditions, limitations on the Company's ability to create, incur or allow certain liens; enter into sale and lease-back transactions; create, assume, incur or guarantee additional indebtedness of the Company's subsidiaries; and consolidate or merge with, or convey, transfer or lease all or substantially all of the Company's and its subsidiaries assets, to another person. At December 31, 2013 the Company was in compliance with these covenants. In the first quarter of 2013, the Company used $224.5 million of the net proceeds of the 5.375% Notes to redeem the outstanding $200.0 million aggregate principal amount of 8.50% Notes and pursuant to the make-whole provision in the Indenture governing the 8.50% Notes, paid a $19.4 million premium and $5.1 million of accrued and unpaid interest. The Company recognized a loss on extinguishment of debt of $25.1 million related to redemption of the 8.50% Notes which included the write off of unamortized debt issuance costs of $4.2 million. Based on quoted market prices in less active markets (a Level 2 input for this financial instrument), the fair value of the 5.375% Notes as of December 31, 2013 was approximately $506.3 million.

Long-term Debt

Senior Convertible Notes

In November 2011, the Company issued $200.0 million aggregate principal amount of zero coupon senior convertible notes due on December 1, 2018 (the “Convertible Notes”) in a private placement offering to TCV VII, L.P., TCV VII(A), L.P., and TCV Member Fund, L.P. A general partner of these funds also serves on the Company’s Board of Directors, and as such, the issuance of the notes is considered a related party transaction. The net proceeds to the Company were approximately $197.8 million. Debt issuance costs of $2.2 million (of which $0.3 million was paid in the year ended December 31, 2012) were recorded in “Other non-current assets” on the Consolidated Balance Sheets and were amortized over the term of the notes as interest expense. At any time following May 28, 2012, the Company could have elected to cause the conversion of the Convertible Notes into shares of the Company’s common stock when specified conditions were satisfied, including that the daily volume weighted average price of the Company’s common stock was equal to or greater than $111.54 for at least 50 trading days during a 65 trading day period prior to the conversion date.

The Company determined that the embedded conversion option in the Convertible Notes did not require separate accounting treatment as a derivative instrument because it was both indexed to the Company's own stock and would be classified in stockholders' equity if freestanding. Additionally, the Convertible Notes did not require or permit any portion of the obligation to be settled in cash and accordingly the liability and equity (conversion option) components were not required to be accounted for separately.

In April 2013, after all specified conditions were satisfied, the Company elected to cause the conversion of all outstanding Convertible Notes with an aggregate principal amount of $200.0 million in accordance with the terms of the Indenture governing such notes. Pursuant to this conversion, the Company issued 2.3 million shares of common stock to the holders of the Convertible Notes at a conversion ratio of 11.6553. The fair market value of one share of common stock on the date of conversion was $216.99 per share.

Senior Notes

In November 2009, the Company issued $200.0 million aggregate principal amount of 8.50% senior notes due November 15, 2017 (the “8.50% Notes”). The net proceeds to the Company were approximately $193.9 million. Debt issuance costs of $6.1 million were recorded in “Other non-current assets” on the Consolidated Balance Sheets and were amortized over the term of the notes as interest expense. The notes were issued at par and were senior unsecured obligations of the Company. Interest was payable semi-annually at a rate of 8.50% per annum on May 15 and November 15 of each year, commencing on May 15, 2010. The 8.50% Notes were repayable in whole or in part upon the occurrence of a change of control, at the option of the holders, at a purchase price in cash equal to 101% of the principal plus accrued interest. The Company could redeem the 8.50% Notes prior to November 15, 2013 in whole or in part at a redemption price of 100% of the principal plus accrued interest, plus a “make-whole” premium.

In February 2013, the Company issued $500.0 million aggregate principal amount of 5.375% senior notes due 2021 (the “5.375% Notes”). The 5.375% Notes were issued at par and are senior unsecured obligations of the Company. Interest is payable semi-annually at a rate of 5.375% per annum on February 1 and August 1 of each year, commencing on August 1, 2013. The 5.375% Notes are repayable in whole or in part upon the occurrence of a change of control, at the option of the holders, at a purchase price in cash equal to 101% of the principal plus accrued interest. The Company may redeem the 5.375% Notes prior to maturity in whole or in part at an amount equal to the principal amount thereof plus accrued and unpaid interest plus a make-whole payment equivalent to the present value of the remaining interest payments through maturity.

The 5.375% Notes include, among other terms and conditions, limitations on the Company's ability to create, incur or allow certain liens; enter into sale and lease-back transactions; create, assume, incur or guarantee additional indebtedness of the Company's subsidiaries; and consolidate or merge with, or convey, transfer or lease all or substantially all of the Company's and its subsidiaries assets, to another person. At December 31, 2013 the Company was in compliance with these covenants.

In the first quarter of 2013, the Company used $224.5 million of the net proceeds of the 5.375% Notes to redeem the outstanding $200.0 million aggregate principal amount of 8.50% Notes and pursuant to the make-whole provision in the Indenture governing the 8.50% Notes, paid a $19.4 million premium and $5.1 million of accrued and unpaid interest. The Company recognized a loss on extinguishment of debt of $25.1 million related to redemption of the 8.50% Notes which included the write off of unamortized debt issuance costs of $4.2 million.

Based on quoted market prices in less active markets (a Level 2 input for this financial instrument), the fair value of the 5.375% Notes as of December 31, 2013 was approximately $506.3 million.