Long-term Debt Senior Convertible Notes (Details)		12 Months Ended
	Aug. 12, 2016 USD ($) $ / shares	Dec. 31, 2019 USD ($) $ / shares	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Senior Convertible Notes [Line Items]
Senior Convertible Notes, net carrying amount		$ 157,263,000	$ 147,894,000
Capped call transaction costs	$ 24,200,000
Capped Call, Cap Price | $ / shares	$ 60.00
Capitalized interest costs		18,500,000	20,600,000	$ 12,600,000
1.50% Senior Convertible Notes Due 2021 [Member]
Senior Convertible Notes [Line Items]
Senior Convertible Notes, principal amount	$ 172,500,000	$ 172,500,000	172,500,000
Senior Convertible Notes, interest rate, stated percentage		1.50%
Proceeds from Debt, Net of Issuance Costs	166,600,000
Senior Convertible Notes, debt issuance costs	(5,900,000)
Senior Convertible Notes, threshold trading days		20
Senior Convertible Notes, threshold consecutive trading days		30
Senior Convertible Notes, threshold percentage of stock price trigger		130.00%
Senior Convertible Notes, threshold business days, trading price trigger		5 days
Senior Convertible Notes, threshold trading days, trading price trigger		5 days
Senior Convertible Notes, principal amount of note		$ 1,000
Senior Convertible Notes, threshold percentage of trading price trigger		98.00%
Senior Convertible Notes, conversion rate		24.6914
Senior Convertible Notes, conversion price | $ / shares		$ 40.50
Senior Convertible Notes, initial fair value of liability component	$ 132,300,000
Senior Convertible Notes, effective interest rate	7.25%
Senior Convertible Notes, initial value of equity component	$ 40,200,000
Senior Convertible Notes, interest expense		$ 11,000,000.0	10,500,000	$ 9,900,000
Senior Convertible Notes, unamortized debt discount		(13,861,000)	(22,313,000)
Unamortized deferred financing costs		(1,376,000)	(2,293,000)
Senior Convertible Notes, net carrying amount		157,263,000	147,894,000
Senior Convertible Notes, net carrying amount, equity component		$ 33,600,000	$ 33,600,000