Stockholders' Equity (Details Textual) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended				1 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Quarterly Dividend	Feb. 28, 2014 Quarterly Dividend Subsequent Event
Stockholders' Equity (Textual) [Abstract]
Remaining number of shares available for repurchase	2,100,000
Repurchase of common stock for tax withholdings, shares	264,000	197,000	232,000
Repurchase of common stock for tax withholdings, value	$ 5.4	$ 3.2	$ 4.4
Carrying amount of the equity component of convertible debt securities outstanding	22.9	22.9
Cash dividend per share of common stock, declared	$ 0.45			$ 0.15	$ 0.15
Cash dividend declared to common stockholders	15.2
Cash dividend paid to common stockholders	$ 14.5