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Stockholders' Equity (Details) - $ / shares	2 Months Ended	12 Months Ended
	Feb. 21, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Jan. 31, 2017	May 31, 2015
Stockholders' equity
Common stock, shares authorized (in shares)		153,000,000	153,000,000
Subsequent Event
Share repurchase activity
Shares repurchased (in shares)	400,000
Average price (in usd per share)	$ 159.91
Preferred Stock
Stockholders' equity
Preferred stock, shares authorized (in shares)		5,000,000.0
Common Stock
Share repurchase activity
Shares repurchased (in shares)		200,000	1,700,000	1,200,000
Average price (in usd per share)		$ 161.16	$ 209.39	$ 204.72
Common Stock | 2017 Authorization
Stockholders' equity
Stock repurchase program, authorized amount (in shares)		200,000
Share repurchase activity
Average price (in usd per share)		$ 161.16
Common Stock | 2017 Authorization | Subsequent Event
Stockholders' equity
Stock repurchase program, authorized amount (in shares)					1,900,000
Common Stock | 2015 Authorization
Stockholders' equity
Stock repurchase program, authorized amount (in shares)						3,000,000
Voting Common Stock
Stockholders' equity
Common stock, shares authorized (in shares)		150,000,000
Class B Non-Voting Common Stock
Stockholders' equity
Common stock, shares authorized (in shares)		3,000,000.0

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The maximum number of common shares permitted to be issued by an entity's charter and bylaws.

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