Obligations Narrative (Details) $ / shares in Units, shares in Millions				3 Months Ended		12 Months Ended
	Jun. 03, 2019 USD ($) day $ / shares	May 31, 2019 USD ($) $ / shares shares	May 31, 2019 USD ($) $ / shares shares	Jun. 30, 2019 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2019 USD ($) day $ / shares shares	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	May 29, 2019 USD ($) $ / shares	Mar. 11, 2015 USD ($) $ / shares	Mar. 09, 2015 shares	Mar. 05, 2015 USD ($)
Debt Instrument [Line Items]
Convertible note hedge		$ 72,000,000.0	$ 72,000,000.0
Class of warrant or right, exercise price of warrants or rights (in dollars per share) | $ / shares		$ 109.43	$ 109.43
Proceeds from issuance of warrants		$ 47,600,000				$ 47,600,000	$ 0	$ 0
Call spread transactions net		24,400,000	$ 24,400,000
Use of proceeds repayment of long term debt		$ 232,700,000	232,700,000	$ 232,700,000
Repayments of long-term debt			$ 221,100,000	$ 221,100,000		221,091,000	0	0
Use of proceeds repurchases of common stock									$ 19,600,000
Use of proceeds repurchases of common stock (in dollars per share) | $ / shares									$ 62.53
Debt issuance costs gross						$ 6,400,000	0	0
Unwind transactions (in shares) | shares						1.3
Proceeds from hedge unwind						$ 9,038,000	0	0
Payment for warrant unwind						4,184,000	0	0
Proceeds for combined unwind transactions net						4,900,000
Loss on extinguishment of debt						5,488,000	0	$ 0
Adjustments to additional paid in capital equity component of convertible debt subsequent adjustments before tax						13,000,000.0
Adjustments to additional paid in capital equity component of convertible debt, subsequent adjustments						10,649,000
Convertible Notes 2020
Debt Instrument [Line Items]
Unamortized debt discount and issuance costs						3,300,000
Convertible Debt | Convertible Notes 2024
Debt Instrument [Line Items]
Debt instrument face amount	$ 400,000,000.0					400,000,000	0
Debt instrument interest rate stated percentage	2.00%
Proceeds from debt net of issuance costs	$ 391,600,000
Debt instrument convertible conversion ratio	12.3018
Debt conversion converted instrument amount	$ 1,000					1,000
Debt instrument convertible conversion price (in dollars per share) | $ / shares	$ 81.29
Debt instrument convertible threshold percentage of stock price trigger	130.00%
Debt instrument convertible stock price trigger (in dollars per share) | $ / shares	$ 105.68
Debt instrument convertible threshold trading days | day	20
Debt instrument convertible threshold consecutive trading days | day	30
Debt instrument redemption price percentage	100.00%
Convertible note hedge (in shares) | shares		4.9	4.9
Class of warrant or right number of securities called by warrants or rights (in shares) | shares		4.9	4.9
Debt instrument convertible carrying amount of liability component	$ 328,000,000.0
Debt instrument convertible carrying amount of equity component	72,000,000.0
Debt instrument convertible carrying amount of equity component net of tax	$ 56,900,000
Debt instrument interest rate effective percentage	6.25%
Debt issuance costs gross	$ 8,400,000
Deferred finance costs own-share lending arrangement issuance costs gross	6,400,000
Debt issuance costs equity component	1,900,000
Debt issuance costs net	$ 1,700,000
Convertible Debt | Convertible Notes 2020
Debt Instrument [Line Items]
Debt instrument face amount					$ 316,000,000.0	$ 94,909,000	316,000,000
Debt instrument interest rate stated percentage	1.50%									1.50%
Debt instrument convertible conversion ratio					14.1559
Debt conversion converted instrument amount					$ 1,000
Debt instrument convertible conversion price (in dollars per share) | $ / shares										$ 70.64
Debt instrument convertible threshold percentage of stock price trigger						130.00%
Debt instrument convertible stock price trigger (in dollars per share) | $ / shares						$ 91.83
Debt instrument convertible threshold trading days | day						20
Debt instrument convertible threshold consecutive trading days | day						30
Convertible note hedge (in shares) | shares											4.4
Class of warrant or right number of securities called by warrants or rights (in shares) | shares											4.4
Class of warrant or right, exercise price of warrants or rights (in dollars per share) | $ / shares						$ 86.34
Debt instrument convertible carrying amount of liability component										$ 256,700,000
Debt instrument convertible carrying amount of equity component										59,300,000
Debt instrument convertible carrying amount of equity component net of tax										$ 38,600,000
Debt instrument interest rate effective percentage										5.89%
Long-term debt						$ 94,900,000
Convertible Notes 2020 | Convertible Notes 2020
Debt Instrument [Line Items]
Debt instrument face amount						494,909,000				$ 316,000,000.0
Senior notes						$ 423,657,000	$ 298,951,000
Convertible Debt 1
Debt Instrument [Line Items]
Senior notes												$ 275,000,000.0
Convertible Note Overallotment
Debt Instrument [Line Items]
Senior notes												$ 41,000,000.0