Convertible Senior Notes (Due 2023) (Details)		1 Months Ended	3 Months Ended
	Mar. 31, 2017 USD ($) $ / shares	Jun. 30, 2016 USD ($) d $ / shares	Mar. 31, 2017 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)
Interest expense
Amortization of debt discount			$ 6,973,000	$ 6,300,000
Senior Notes | Convertible Senior Notes Due 2023
Debt Instrument [Line Items]
Principal	$ 402,500,000	$ 402,500,000	402,500,000		$ 402,500,000
Interest rate		2.75%
Proceeds from offering		$ 390,800,000
Trading days | d		20
Redemption consecutive trading period		30 days
Redemption stock price conversion threshold (greater than or equal to)		130.00%
Consecutive measurement period		5 days
Percent of trading price (less than)		98.00%
Consecutive trading days		50 days
Conversion ratio		0.0204198
Conversion price (USD per share) | $ / shares		$ 48.97
Redemption trading period		19 days
Percent of principal amount plus accrued and unpaid interest		100.00%
Debt default principal amount percentage		25.00%
Debt instrument, term		7 years
Carrying amount, equity component	101,000,000		101,000,000
Net deferred tax liabilities		$ 33,500,000
Liability component
Principal	402,500,000	402,500,000	402,500,000		402,500,000
Less: Debt discount, net	(100,086,000)		(100,086,000)		(103,162,000)
Net carrying amount	$ 302,414,000		$ 302,414,000		$ 299,338,000
Remaining contractual life			6 years 3 months 15 days
Interest expense
Contractual interest expense			$ 2,759,000	0
Amortization of debt discount			3,075,000	0
Total			$ 5,834,000	$ 0
Effective interest rate of the liability component	7.50%		7.50%	0.00%
Senior Notes | Convertible Senior Notes Due 2023 | Call Option
Interest expense
Payment of cost of capped call transactions		$ 33,900,000
Cap price (USD per share) | $ / shares	$ 64.68
Significant Other Observable Inputs (Level 2) | Senior Notes | Convertible Senior Notes Due 2023
Liability component
Fair value of Notes	$ 485,900,000		$ 485,900,000