Repurchase Program (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016	Feb. 29, 2016
Equity, Class of Treasury Stock [Line Items]
Gain on extinguishment of debt	$ 0	$ 0	$ 0	$ 1,894,000
Stock repurchase program, remaining authorized repurchase amount	$ 33,500,000		$ 33,500,000
Share repurchase program
Equity, Class of Treasury Stock [Line Items]
Treasury stock, shares, acquired			0	0
Share repurchase program | Senior notes
Equity, Class of Treasury Stock [Line Items]
Debt instrument, repurchased face amount						$ 11,200,000
Convertible Notes due 2017 | Senior notes
Equity, Class of Treasury Stock [Line Items]
Purchase of senior notes		9,200,000		$ 9,200,000
Gain on extinguishment of debt		$ 1,900,000
Convertible Notes due 2017 | Share repurchase program
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, authorized amount					$ 100,000,000.0
Convertible Notes due 2021 | Share repurchase program
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, authorized amount					$ 78,100,000