Stockholders' Equity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Stockholders' Equity, Number of Shares, Par Value and Other Disclosures [Abstract]
Preferred stock, shares authorized	100,000		100,000	100,000
Preferred stock, par value per share	$ 100		$ 100	$ 100
Common stock, shares authorized	500,000,000		500,000,000	500,000,000
Common stock, par value per share	$ 1.00		$ 1.00	$ 1.00
Common stock, shares issued	257,822,352		257,822,352	256,992,261
Number of treasury shares held	112,905,810		112,905,810	102,168,868
Share Repurchases [Line Items]
ExpectedShareRepurchaseInNovember2017			$ 1,000,000
Accelerated Share Repurchases, Settlement (Payment) or Receipt	$ 700,000		700,000
Payments for Repurchase of Common Stock			894,977	$ 105,023	$ 0
January 2015 Authorization [Member]
Share Repurchases [Line Items]
Payments for Repurchase of Common Stock			$ 44,977	$ 105,023
Shares repurchased			440,608	1,059,682
Average price per share for repurchased shares (in dollars per share)			$ 102.08	$ 99.11
Remaining number of shares authorized to be repurchased	5,271,168		5,271,168
February 2018 Authorization [Member]
Share Repurchases [Line Items]
Accelerated Share Repurchases, Final Price Paid Per Share			$ 81.94
Accelerated Shares Repurchased	1,463,815	7,078,751	8,542,566
Number of shares authorized to be repurchased	20,000,000		20,000,000
Payments for Repurchase of Common Stock			$ 150,000
Shares repurchased			1,753,768
Average price per share for repurchased shares (in dollars per share)			$ 85.53
Remaining number of shares authorized to be repurchased	9,703,666		9,703,666