Convertible Senior Notes (Due 2023) (Details)	1 Months Ended	3 Months Ended		6 Months Ended
	Jun. 30, 2016 USD ($) d $ / shares	Jun. 30, 2016 USD ($) $ / shares	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($) $ / shares	Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Interest expense
Amortization of debt discount				$ 12,770,000	$ 11,436,000
Senior Notes [Member] | Convertible Senior Notes Due 2023 [Member]
Debt Instrument [Line Items]
Principal	$ 402,500,000	$ 402,500,000		$ 402,500,000		$ 0
Interest rate	2.75%	2.75%		2.75%
Proceeds from offering	$ 390,800,000
Trading period | 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%
Trading period	50 days
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 of equity component	$ 101,000,000	$ 101,000,000		$ 101,000,000
Net deferred tax liabilities	37,300,000	37,300,000		37,300,000
Liability component
Principal	402,500,000	402,500,000		402,500,000		0
Less: Debt discount, net	(109,082,000)	(109,082,000)		(109,082,000)		0
Net carrying amount	293,418,000	293,418,000		293,418,000		$ 0
Fair value of Notes	$ 390,100,000	390,100,000		$ 390,100,000
Remaining contractual life				7 years 15 days
Interest expense
Contractual interest expense		604,000	$ 0	$ 604,000	0
Amortization of debt discount		727,000	0	727,000	0
Total		$ 1,331,000	$ 0	$ 1,331,000	$ 0
Effective interest rate of the liability component	7.50%	7.50%		7.50%
Senior Notes [Member] | Convertible Senior Notes Due 2023 [Member] | Call Option [Member]
Interest expense
Payment of cost of capped call transactions	$ 33,900,000
Cap price (USD per share) | $ / shares	$ 64.68