Convertible Senior Notes - Due 2017 (Details)	1 Months Ended		3 Months Ended	12 Months Ended
	Jun. 30, 2016 USD ($)	Jun. 30, 2012 USD ($) d $ / shares	Dec. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Debt Instrument [Line Items]
Debt, repurchase amount				$ 323,225,000	$ 0	$ 0
Loss on extinguishment of debt				5,380,000	0	0
Reduction of additional paid-in capital for difference between consideration transferred and fair value of liability component				108,725,000
Equity component recorded at issuance				98,085,000	37,177,000
Interest expense
Amortization of debt discount				26,182,000	23,676,000	11,920,000
Senior Notes [Member] | Convertible Senior Notes Due 2017 [Member]
Debt Instrument [Line Items]
Principal		$ 275,000,000	$ 55,000,000	55,000,000	275,000,000
Interest rate		1.375%
Proceeds from offering		$ 266,200,000
Debt, repurchase amount	$ 323,200,000
Debt, aggregate principal amount repurchased	220,000,000
Cash receipt for settlement of outstanding bond hedges and warrants	12,600,000
Loss on extinguishment of debt				5,400,000
Reduction of additional paid-in capital for difference between consideration transferred and fair value of liability component	$ 108,700,000
Trading period | d		20
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%
Number of trading days prior to maturity that debt may be converted			2 days
Conversion ratio		0.0358038
Conversion price (usd per share) | $ / shares		$ 27.93
Percent of principal amount plus accrued and unpaid interest		100.00%
Debt default principal amount percentage		25.00%
Debt instrument, term		5 years
Equity component recorded at issuance		$ 55,700,000
Carrying amount of equity component			$ 11,100,000	11,100,000
Deferred tax asset		1,500,000	300,000	300,000
Liability component
Principal		$ 275,000,000	55,000,000	55,000,000	275,000,000
Less: Debt discount, net			(1,251,000)	(1,251,000)	(19,527,000)
Net carrying amount			$ 53,749,000	$ 53,749,000	255,473,000
Remaining contractual life				5 months 1 day
Interest expense
Contractual interest expense				$ 2,101,000	3,781,000	3,781,000
Amortization of debt discount				7,395,000	12,734,000	11,920,000
Total				$ 9,496,000	$ 16,515,000	$ 15,701,000
Effective interest rate of the liability component			6.02%	6.02%	6.02%	6.02%
Senior Notes [Member] | Convertible Senior Notes Due 2017 [Member] | Level 2 [Member]
Liability component
Fair value of Notes			$ 54,800,000	$ 54,800,000