Debt (Convertible Debt) (Details)			12 Months Ended
	Nov. 13, 2017 USD ($)	May 12, 2017 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) Integer $ / shares shares	Dec. 31, 2018 USD ($) shares	Dec. 31, 2017 USD ($)	Dec. 13, 2019 USD ($)	Sep. 27, 2019 USD ($)	May 24, 2017 USD ($)	Nov. 30, 2010 USD ($)
Debt Instrument
Amortization of debt issuance costs			$ 1,996,000	$ 1,806,000	$ 2,014,000
Proceeds from convertible debt			$ 0	0	200,000,000
Purchase of call options related to convertible notes		$ 20,500,000
Share Price | $ / shares			$ 65.92
Debt Instrument, Convertible, If-converted Value in Excess of Principal			$ 2,000,000.0
Convertible Debt [Abstract]
Capped call transaction cap price (in dollars per share) | $ / shares		$ 88.7570
Effective interest rate								5.00%
Interest Expense, Debt [Abstract]
Accretion of convertible notes discount			2,760,000	2,596,000	3,410,000
Proceeds from bond hedge settlement convertible notes			0	0	58,564,000
Gain (Loss) on Extinguishment of Debt			0	0	(137,000)
2024 Notes
Debt Instrument
Convertible notes face amount			199,500,000	200,000,000				$ 200,000,000.0
Unamortized discount			13,440,000	16,251,000
Carrying value of liability			186,060,000	183,749,000				179,500,000
Amount before overallotment		$ 175,000,000.0
Debt Instrument face amount overallotment								25,000,000.0
Annual principal interest rate		3.25%
Multiple, Debt Instrument		$ 1,000					$ 1,000
Debt Instrument, Repurchased Face Amount							$ 500,000
Percent, Debt Instrument, Repurchase Amount							0.25%
Equity component			20,408,000	20,459,000				20,500,000
Deferred finance costs, gross					(7,400,000)
Amortization of debt issuance costs			$ 900,000	800,000	500,000
Convertible Debt [Abstract]
Conversion rate		15.3227
Conversion price (in dollars per share) | $ / shares		$ 65.2626
Contingent conversion price (in dollars per shares) | $ / shares		$ 84.8413
Aggregate shares to be issued upon conversion, convertible (in shares) | shares			3,056,879
Convertible debt stock price threshold trigger percent			130.00%
Convertible debt trading days threshold | Integer			20
Convertible, threshold consecutive trading days | Integer			30
Percentage of average of closing price of common stock			98.00%
Debt issuance costs, recorded to APIC								700,000
Debt issuance costs, recorded as contra-debt								$ 6,700,000
Interest Expense, Debt [Abstract]
Contractual coupon rate of interest			$ 6,503,000	6,500,000	4,207,000
Accretion of convertible notes discount			2,753,000	2,596,000	1,612,000
Interest expense			9,256,000	$ 9,096,000	5,819,000
2017 Notes
Debt Instrument
Convertible notes face amount									$ 115,000,000.0
Carrying value of liability		$ 113,943,000
Options issued in debt conversion (in shares) | shares		624,044		114,778
Annual principal interest rate									3.25%
Debt Instrument, Repurchased Face Amount	$ 11,500,000	$ 103,500,000
Convertible Debt [Abstract]
Effective interest rate		3.00%
Interest Expense, Debt [Abstract]
Contractual coupon rate of interest					3,300,000
Accretion of convertible notes discount		$ 1,000,000.0			1,800,000
Repurchase of debt fair value equity component		60,000,000.0
Convertible debt repurchased carrying value		102,548,000
Repurchase of debt fair value debt component		103,637,000
Gain loss) on extinguishment of debt, before write off of debt issuance cost					(1,089,000)
Write off of Deferred Debt Issuance Cost					297,000
Proceeds from bond hedge settlement convertible notes		$ 58,600,000
Percent of repurchase principal	10.00%	90.00%
Debt Instrument, Repurchase Amount		$ 165,300,000
Gain (Loss) on Extinguishment of Debt					(1,386,000)
Stock conversion amount					7,500,000
Revolving Credit Facility
Debt Instrument
Amortization of debt issuance costs			1,000,000.0
Credit Agreement 2019 [Member] | Revolving Credit Facility
Interest Expense, Debt [Abstract]
Line of credit, credit agreement			$ 800,000,000			$ 800,000,000.0
Credit Agreement 2015 | Revolving Credit Facility
Debt Instrument
Amortization of debt issuance costs				$ 1,000,000	$ 1,000,000
Interest Expense, Debt [Abstract]
Line of credit, credit agreement				$ 600,000,000