Debt (Details) (USD $)	9 Months Ended					0 Months Ended		0 Months Ended	1 Months Ended								0 Months Ended		0 Months Ended			0 Months Ended		0 Months Ended			0 Months Ended			0 Months Ended				0 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Jun. 30, 2012 Revolving Credit Facility [Member]	Jun. 13, 2013 First Credit Amendment [Member] Revolving Credit Facility [Member]	Jan. 23, 2014 Second Credit Amendment [Member] Revolving Credit Facility [Member]	Jan. 23, 2014 Second Credit Amendment [Member] Revolving Credit Facility [Member]	Jan. 23, 2014 Second Credit Amendment [Member] Revolving Credit Facility [Member] Prime Rate [Member]	Aug. 31, 2014 Convertible Debt 2021 Notes [Member] D	Sep. 30, 2014 Convertible Debt 2021 Notes [Member]	Dec. 31, 2013 Convertible Debt 2021 Notes [Member]	Jan. 23, 2014 Additional Term Loan [Member] Second Credit Amendment [Member]	Sep. 30, 2014 Term Loans [Member]	Jan. 23, 2014 Term Loans [Member]	Dec. 31, 2013 Term Loans [Member]	Jun. 30, 2012 Term Loans [Member]	Jun. 13, 2013 Term Loans [Member] First Credit Amendment [Member]	Jun. 13, 2013 Term Loans [Member] First Credit Amendment [Member]	Jan. 23, 2014 Term Loans [Member] Second Credit Amendment [Member]	Jan. 23, 2014 Term Loans [Member] Second Credit Amendment [Member]	Jan. 23, 2014 Term Loans [Member] Second Credit Amendment [Member] LIBOR [Member]	Jan. 23, 2014 Term Loans [Member] Second Credit Amendment [Member] Prime Rate [Member]	Jan. 23, 2014 Term Loans [Member] Second Credit Amendment [Member] Prime Rate [Member]	Jan. 23, 2014 Term Loans [Member] Second Credit Amendment [Member] Revolving Credit Facility [Member] LIBOR [Member]	Sep. 30, 2014 Line of Credit [Member] Revolving Credit Facility [Member]	Jan. 23, 2014 Line of Credit [Member] Revolving Credit Facility [Member]	Jan. 23, 2014 Rate One [Member] Second Credit Amendment [Member] Revolving Credit Facility [Member]	Jan. 23, 2014 Rate One [Member] Second Credit Amendment [Member] Revolving Credit Facility [Member]	Jan. 23, 2014 Rate One [Member] Term Loans [Member] Second Credit Amendment [Member]	Jan. 23, 2014 Rate Two [Member] Second Credit Amendment [Member] Revolving Credit Facility [Member]	Jan. 23, 2014 Rate Two [Member] Second Credit Amendment [Member] Revolving Credit Facility [Member]	Jan. 23, 2014 Rate Two [Member] Term Loans [Member] Second Credit Amendment [Member]	Jan. 23, 2014 Rate Three [Member] Term Loans [Member] Second Credit Amendment [Member]	Jan. 23, 2014 Maximum [Member] Rate Two [Member] Term Loans [Member] Second Credit Amendment [Member]	Jan. 23, 2014 Maximum [Member] Rate Three [Member] Term Loans [Member] Second Credit Amendment [Member]	Jan. 23, 2014 Minimum [Member] Rate Two [Member] Term Loans [Member] Second Credit Amendment [Member]
Debt Instrument [Line Items]
Principle amount of debt									$ 575,000,000			$ 350,000,000		$ 554,400,000		$ 475,000,000.0		$ 557,200,000		$ 904,400,000
Interest rate									1.875%	1.875%			3.25%
Net proceeds from issuance exchangeable senior notes									558,900,000
Frequency of periodic payment									payable semi-annually in cash in arrears on February 15 and August 15 of each year										quarterly
Percentage of conversion price									130.00%
Number of trading days									20
Number of consecutive days in trading period									30 days
Conversion rate of shares									5.0057
Conversion denominator									1,000
Debt conversion price (in dollars per share)									$ 199.77
Effective interest rate										6.40%			4.10%
Debt term									7 years
Debt issuance costs									16,100,000
Carrying value of the equity component										126,900,000
Credit facility borrowing capacity				100,000,000.0	200,000,000		425,000,000
Repayments of Secured Debt	7,090,000	464,517,000															457,200,000
Interest rate reduction in basis points					1.50%													1.50%		0.25%								0.25%			0.50%
Long-term Debt	1,340,784,000		549,976,000							446,448,000	0		892,402,000		549,976,000										0	300,000,000
Debt maturity date						Jun. 12, 2017													Jun. 12, 2018
Basis spread on variable rate								1.50%														1.50%		2.50%
Term loan interest rate minimum percentage																					0.75%		1.75%
Commitment fee on credit facility, percentage																											0.25%			0.50%
Mandatory prepayments as percentage of excess cash flow beginning in 2014																													50.00%			25.00%	0.00%
Secured leverage ratio																																		2.25	1.25	1.25
Percentage of principal amount for repayment																			1.00%
Current portion of long-term debt	9,444,000		5,572,000
Deferred financing costs, gross														21,700,000												5,400,000
Unamortized discount										$ 128,552,000	$ 0			$ 6,100,000