Earnings Per Share (Schedule of Convertible Notes Premium Share Information) (Details) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015 shares	Jun. 30, 2014 USD ($) shares $ / shares	Jun. 30, 2015 shares	Jun. 30, 2014 USD ($) shares $ / shares
Convertible Debt [Member]
Earnings Per Share [Line Items]
Premium shares (in shares)	0	7,711	0	8,066
2011 4.25% Notes [Member]
Earnings Per Share [Line Items]
Per share price, actual average (in dollars per share) | $ / shares		$ 37.68		$ 37.82
Premium value (in dollars) | $		$ 139,170		$ 140,047
2011 4.25% Notes [Member] | Convertible Debt [Member]
Earnings Per Share [Line Items]
Premium shares (in shares)		3,693		3,703
2011 4.25% Notes [Member] | Common Stock [Member]
Earnings Per Share [Line Items]
Number of conversion shares, principal amount (in shares)		6,268		6,268