Convertible Senior Notes (Due 2017) (Details) - USD ($)	1 Months Ended		3 Months Ended
	Jun. 30, 2016	Jun. 30, 2012	Mar. 31, 2017	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2016
Interest expense
Amortization of debt discount			$ 6,973,000		$ 6,300,000
Senior Notes | Convertible Senior Notes Due 2017
Debt Instrument [Line Items]
Principal		$ 275,000,000	55,000,000			$ 55,000,000
Interest rate		1.375%
Proceeds from offering		$ 266,200,000
Debt, repurchase amount	$ 323,200,000
Debt, aggregate principal amount repurchased	220,000,000			$ 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
Conversion ratio		0.0358038
Conversion price (USD per share)		$ 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		$ 54,200,000
Carrying amount, equity component			10,800,000
Deferred tax asset, hedging		1,500,000	300,000
Liability component
Principal		$ 275,000,000	55,000,000			55,000,000
Less: Debt discount, net			(540,000)			(1,251,000)
Net carrying amount			$ 54,460,000			$ 53,749,000
Remaining contractual life			2 months 1 day
Interest expense
Contractual interest expense			$ 189,000		945,000
Amortization of debt discount			711,000		3,326,000
Total			$ 900,000		$ 4,271,000
Effective interest rate of the liability component			6.02%		6.02%
Significant Other Observable Inputs (Level 2) | Senior Notes | Convertible Senior Notes Due 2017
Liability component
Fair value of Notes			$ 96,700,000