Convertible Senior Notes - Due 2023 (Details)		1 Months Ended	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($) $ / shares	Jun. 30, 2016 USD ($) d $ / shares	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($) $ / shares	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($) $ / shares	Dec. 31, 2016 USD ($)
Interest expense
Amortization of debt discount					$ 13,822,000	$ 12,770,000
Senior Notes | Convertible Senior Notes Due 2023
Debt Instrument [Line Items]
Principal	$ 402,500,000	$ 402,500,000	$ 402,500,000	$ 402,500,000	402,500,000	$ 402,500,000	$ 402,500,000
Interest rate		2.75%		2.75%		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%		98.00%		98.00%
Consecutive trading days | d		50
Conversion ratio		0.0204198
Conversion price (USD per share) | $ / shares		$ 48.97		$ 48.97		$ 48.97
Redemption trading period		19 days
Percent of principal amount plus accrued and unpaid interest		100.00%		100.00%		100.00%
Debt default principal amount percentage		25.00%
Debt instrument, term		7 years
Carrying amount, equity component	101,000,000		101,000,000		101,000,000
Net deferred tax liabilities		$ 33,500,000		$ 33,500,000		$ 33,500,000
Liability component
Principal	402,500,000	$ 402,500,000	402,500,000	402,500,000	402,500,000	402,500,000	402,500,000
Less: Debt discount, net	(96,983,000)		(96,983,000)		(96,983,000)		(103,162,000)
Net carrying amount	$ 305,517,000		305,517,000		$ 305,517,000		$ 299,338,000
Remaining contractual life					6 years 15 days
Interest expense
Contractual interest expense			2,767,000	604,000	$ 5,526,000	604,000
Amortization of debt discount			3,104,000	727,000	6,179,000	727,000
Total			$ 5,871,000	$ 1,331,000	$ 11,705,000	$ 1,331,000
Effective interest rate of the liability component	7.50%	7.50%	7.50%	7.50%	7.50%	7.50%
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	$ 425,000,000		$ 425,000,000		$ 425,000,000