Stock Repurchase (Shares Repurchased) (Details) - $ / shares	1 Months Ended												12 Months Ended
	Dec. 31, 2015	Nov. 30, 2015	Oct. 31, 2015	Sep. 30, 2015	Aug. 31, 2015	Jul. 31, 2015	Jun. 30, 2015	May. 31, 2015	Apr. 30, 2015	Mar. 31, 2015	Feb. 28, 2015	Jan. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Class of Stock Disclosures [Abstract]
Number of Shares Purchased	0	0	924,960	0	67,436	303,807	482,586	472,000	640,000	645,000	120,000	529,100	4,184,889	3,298,490	7,707,014
Average Price Paid Per Share	$ 0.00	$ 0.00	$ 80.26	$ 0.00	$ 73.67	$ 70.98	$ 67.19	$ 64.89	$ 61.20	$ 61.50	$ 61.07	$ 65.51	$ 68.02
Total Number of Shares Purchased as Part of Publicly Announced Programs	0	0	924,960	0	67,436	303,807	482,586	472,000	640,000	645,000	120,000	529,100	4,184,889