Stock Repurchase Plans (Details) (USD $)	0 Months Ended					6 Months Ended		12 Months Ended
	Jul. 26, 2013	Jan. 04, 2013	Dec. 11, 2012	Jan. 03, 2012	Feb. 24, 2011	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	Dec. 31, 2011
Stock repurchase program
Amount of shares authorized to be repurchased under Stock Repurchase Program			$ 500,000,000	$ 250,000,000	$ 60,000,000
Period over which shares are authorized to be repurchased			3 years	4 years	3 years
Total number of shares purchased	12,286,000	578,000						8,499,000	3,235,000
Value of shares repurchased	410,200,000	18,000,000				403,663,000	98,401,000	232,000,000	60,000,000
Average price paid per share (in dollars per share)	$ 33.38	$ 31.16
Permitted dollar value of repurchases under the plans or programs	$ 89,800,000