Share Repurchase Program and Treasury Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Share Repurchase Program and Treasury Stock (Textuals) [Abstract]
Authorized amount under share repurchase program	$ 1,360,000
Shares Purchased Under Share Repurchase Program	25,000,000
Repurchases of common stock	$ (125,000)	$ (123,745)	$ (494,966)
Number of shares repurchased	390,337	400,845
Average price of share repurchased, per share	$ 320.22	$ 308.69
Exercise of stock options and restricted stock units, shares reissued	59,321	125,398