Capital Stock (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Common stock, shares authorized	100,000,000	100,000,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	5,000,000
Preferred stock, par value	$ 0.01
Common Stock, Shares, Outstanding	79,649,946	78,855,547	78,112,032
Treasury stock, shares held	2,672,930	2,478,084	2,334,137
Preferred stock, shares issued	0
Common Shares Outstanding and Treasury Shares Held Rollforward [Table]
Common shares outstanding, beginning balance	78,855,547	78,112,032	77,423,415
Exercise of common stock options, net	290,369	373,106	580,097
Grants of restricted stock, net	504,030	370,409	108,520
Common shares outstanding, ending balance	79,649,946	78,855,547	78,112,032
Treasury stock, beginning balance	2,478,084	2,334,137	2,249,959
Shares received upon exercise of common stock options	189,469	119,477	81,616
Shares received upon vesting of restricted stock, net	5,377	24,470	2,562
Treasury stock, ending balance	2,672,930	2,478,084	2,334,137
Amount authorized under stock repurchase program	$ 20,000,000
Amount repurchased under the stock repurchase program in the period	$ 0