Earnings Per Share (Narrative) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		1 Months Ended	52 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	May 08, 2015	May 08, 2015
Earnings Per Share
Common stock repurchased, shares	650	149
Common stock repurchased, average price per share	$ 207.50	$ 148.18
Common stock repurchased, value	$ 134,803	$ 22,065
Subsequent Event [Member]
Earnings Per Share
Common stock repurchased, shares			600	47,600
Common stock repurchased, average price per share			$ 218.25	$ 94.29
Common stock repurchased, value			$ 133,900	$ 4,500,000