Equity	9 Months Ended
Sep. 30, 2013
Stockholders' Equity Note [Abstract]
Equity	Equity On September 18, 2013, a dividend of $0.45 per share was paid to stockholders of record on September 4, 2013. Dividends include dividend equivalents of $4.7 million and $4.2 million, which were paid on outstanding restricted stock units during the nine months ended September 30, 2013 and September 30, 2012, respectively. During the nine months ended September 30, 2013, 662,569 restricted stock units vested and were issued as common stock of which the Company is deemed to have repurchased 214,303 shares at an average price of $57.22 per share in conjunction with the payment of tax liabilities in respect of stock delivered to its employees in settlement of restricted stock units. In addition, during the nine months ended September 30, 2013, the Company repurchased in open market transactions 853,870 shares of its common stock at an average price of $49.81 per share. During the nine months ended September 30, 2012, 632,794 restricted stock units vested and were issued as common stock of which the Company is deemed to have repurchased 176,781 shares at an average price of $45.21 per share in conjunction with the payment of tax liabilities in respect of stock delivered to its employees in settlement of restricted stock units. In addition, during the nine months ended September 30, 2012, the Company repurchased in open market transactions 859,006 shares of its common stock at an average price of $37.84 per share. In connection with the acquisition of Caliburn, 1,099,877 shares of contingent convertible preferred stock ("Performance Stock") were issued. The Performance Stock, which does not pay dividends, was issued in tranches of 659,926 shares and 439,951 shares and converts to shares of the Company's common stock promptly after the third and fifth anniversary of the closing of the acquisition, respectively, if certain separate revenue targets are achieved. The revenue target for the first tranche was achieved and on April 1, 2013, the third anniversary of the closing, 659,926 shares of Performance Stock, which had a fair value of $32.5 million at the acquisition date, were converted to common stock. If the revenue target for the second tranche is achieved the Performance Stock will be converted to common stock on April 1, 2015. If the revenue target for the second tranche is not achieved, the Performance Stock in that tranche will be canceled.

Equity

9 Months Ended

Sep. 30, 2013

Stockholders' Equity Note [Abstract]

On September 18, 2013, a dividend of $0.45 per share was paid to stockholders of record on September 4, 2013. Dividends include dividend equivalents of $4.7 million and $4.2 million, which were paid on outstanding restricted stock units during the nine months ended September 30, 2013 and September 30, 2012, respectively.

During the nine months ended September 30, 2013, 662,569 restricted stock units vested and were issued as common stock of which the Company is deemed to have repurchased 214,303 shares at an average price of $57.22 per share in conjunction with the payment of tax liabilities in respect of stock delivered to its employees in settlement of restricted stock units. In addition, during the nine months ended September 30, 2013, the Company repurchased in open market transactions 853,870 shares of its common stock at an average price of $49.81 per share.

During the nine months ended September 30, 2012, 632,794 restricted stock units vested and were issued as common stock of which the Company is deemed to have repurchased 176,781 shares at an average price of $45.21 per share in conjunction with the payment of tax liabilities in respect of stock delivered to its employees in settlement of restricted stock units. In addition, during the nine months ended September 30, 2012, the Company repurchased in open market transactions 859,006 shares of its common stock at an average price of $37.84 per share.

In connection with the acquisition of Caliburn, 1,099,877 shares of contingent convertible preferred stock ("Performance Stock") were issued. The Performance Stock, which does not pay dividends, was issued in tranches of 659,926 shares and 439,951 shares and converts to shares of the Company's common stock promptly after the third and fifth anniversary of the closing of the acquisition, respectively, if certain separate revenue targets are achieved. The revenue target for the first tranche was achieved and on April 1, 2013, the third anniversary of the closing, 659,926 shares of Performance Stock, which had a fair value of $32.5 million at the acquisition date, were converted to common stock. If the revenue target for the second tranche is achieved the Performance Stock will be converted to common stock on April 1, 2015. If the revenue target for the second tranche is not achieved, the Performance Stock in that tranche will be canceled.