Earnings Per Share (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Reconciliation of basic to diluted weighted average shares outstanding
Weighted average shares outstanding - basic (in shares)	87,674,000	86,196,000	87,408,000	86,030,000
Dilutive effect of stock options (in shares)	1,200,000	1,907,000	1,336,000	2,131,000
Dilutive effect of restricted stock awards and units (in shares)	149,000	248,000	175,000	268,000
Weighted average shares outstanding - diluted (in shares)	89,023,000	88,351,000	88,919,000	88,429,000
Stock options
Anti-dilutive securities
Anti-dilutive securities excluded from diluted earnings per share calculations (in shares)	1,413,369	897,368	1,375,346	485,837
Restricted Stock Units
Anti-dilutive securities
Anti-dilutive securities excluded from diluted earnings per share calculations (in shares)	189,278	50,721	102,847	50,818