Capital Stock (Details Textual) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Feb. 28, 2016
Equity, Class of Treasury Stock [Line Items]
Treasury stock, common, shares		15,162,050	15,302,345	15,210,233
Preferred stock, par or stated value per share		$ 0.01
Preferred stock, shares outstanding		0	0	0
Treasury shares purchased				$ 50,596,000
Share repurchase program [Member]
Equity, Class of Treasury Stock [Line Items]
Treasury stock, shares, acquired		0	0	4,317,278
Stock repurchase program, authorized amount		$ 100,000,000
Treasury stock acquired, average cost per share				$ 11.72
Stock repurchase program, remaining authorized repurchase amount		$ 33,500,000
Employee Stock Purchase Plan [Member]
Equity, Class of Treasury Stock [Line Items]
Preferred stock, shares authorized		1,000,000
Treasury stock, shares, acquired		234,901	292,168	215,760
Treasury stock issued during period		375,196	200,056	155,650
Restricted stock [Member]
Equity, Class of Treasury Stock [Line Items]
Treasury shares purchased		$ 1,229,000	$ 2,283,000	$ 2,534,000
Convertible Notes due 2017 [Member] | Convertible debt [Member] | Share repurchase program [Member]
Equity, Class of Treasury Stock [Line Items]
Repurchased face amount					$ 11,200,000
Convertible Notes due 2017 [Member] | Senior notes [Member]
Equity, Class of Treasury Stock [Line Items]
Repurchased face amount		89,300,000
Debt instrument, face amount		172,500,000.0
Convertible Notes due 2017 [Member] | Senior notes [Member] | Share repurchase program [Member]
Equity, Class of Treasury Stock [Line Items]
Purchase Of senior notes	$ 9,200,000
Debt authorized repurchase amount		$ 78,100,000