Debt, Convertible Note (Details)		3 Months Ended	9 Months Ended
	Jun. 16, 2016 USD ($)	Sep. 30, 2017 USD ($) $ / shares	Sep. 30, 2017 USD ($) d $ / shares shares	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Net Carrying Amount of Liability Component [Abstract]
Unamortized debt discount (conversion option)		$ (10,000,000)	$ (10,000,000)
Unamortized debt discount (issuance costs)		(4,400,000)	(4,400,000)
Debt issuance costs			0	$ 6,596,000
Convertible Note [Member]
Convertible Debt [Abstract]
Original principal amount	$ 210,000,000	$ 210,000,000	$ 210,000,000
Interest rate		4.75%	4.75%
Maturity date			Jun. 15, 2020
Redemption price, percentage of principal amount redeemed			100.00%
Threshold percentage of stock price trigger			180.00%
Threshold trading days | d			20
Threshold final trading days | d			3
Threshold consecutive trading days | d			30
Principal amount increments that can be repurchased upon a change in control or termination of trading of common stock			$ 1,000
Principal amount increments that can be converted			$ 1,000
Holding period following issue date before notes can be converted			6 months
Initial conversion rate (in shares) | shares			21.5054
Initial conversion price (in dollars per share) | $ / shares		$ 46.50	$ 46.50
Proceeds from issuance of notes	210,000,000
Liability component of convertible notes	199,100,000
Equity component of convertible notes allocated to additional paid-in capital	$ 10,900,000
Effective interest rate		7.10%	7.10%
Net Carrying Amount of Liability Component [Abstract]
Principal		$ 210,000,000	$ 210,000,000		$ 210,000,000
Unamortized debt discount (conversion option)		(7,731,000)	(7,731,000)
Total long-term debt, net		202,269,000	202,269,000
Unamortized debt discount (issuance costs)		(4,424,000)	(4,424,000)
Net carrying amount		197,845,000	197,845,000
Debt issuance costs			6,600,000
Additions to deferred financing cost			6,300,000
Adjustments to additional paid-in capital for debt issuance costs			$ 300,000
Interest expense		3,500,000
Contractual interest		2,500,000
Amortization of debt issuance costs and debt discount		$ 1,000,000