Stockholders' Equity (Details)								2 Months Ended			12 Months Ended
	Jul. 11, 2016 shares	May 09, 2016 USD ($) shares	Apr. 19, 2016 shares	Feb. 17, 2016 USD ($) shares	Jan. 19, 2016 shares	Nov. 12, 2015 USD ($) $ / shares shares	Oct. 30, 2015 dividend $ / shares	Jul. 11, 2016 $ / shares shares	Apr. 19, 2016 $ / shares shares	Jan. 19, 2016 $ / shares shares	Dec. 31, 2017 $ / shares	Dec. 31, 2016 $ / shares	Dec. 31, 2015 $ / shares	Sep. 30, 2015 USD ($)	Aug. 20, 2014 USD ($) $ / shares
Class of Warrant or Right [Line Items]
Authorized amount for stock repurchase program		$ 400,000,000		$ 400,000,000		$ 400,000,000
Authorized amount for accelerated stock repurchase program		$ 400,000,000		$ 400,000,000		$ 400,000,000
Accelerated share repurchased, number of shares purchased (shares) | shares	1,104,162	3,964,812	861,235	4,222,193	970,609	4,140,788		5,068,974.000	5,083,428	5,111,397
Average price per share paid for stock repurchased for accelerated stock repurchases (in dollars per share) | $ / shares								$ 78.91	$ 78.69	$ 78.26
Number of dividends declared | dividend							2
Dividends declared for common stock (in dollars per share) | $ / shares						$ 2.00	$ 2.00				$ 2.87	$ 2.75	$ 6.63
Par value of common stock (in dollars per share) | $ / shares											$ 0.01	$ 0.01			$ 0.01
Maximum price of common stock available to be issued															$ 500,000,000
2015 Stock Buyback Program
Class of Warrant or Right [Line Items]
Authorized amount for stock repurchase program														$ 1,200,000,000