Shareholders' Equity - Additional Information (Details)					12 Months Ended
	Jun. 09, 2017 USD ($) $ / shares shares	Nov. 19, 2015 USD ($) $ / shares shares	Mar. 13, 2008 right / shares shares / right	Mar. 13, 2008 right / shares shares / right firm	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 USD ($) shares	Nov. 29, 2017 USD ($)	Apr. 25, 2017 USD ($)	Feb. 29, 2016 USD ($)	Feb. 24, 2016 USD ($)	Dec. 31, 2015 USD ($)	Oct. 28, 2015 USD ($)
Distribution Made to Limited Partner [Line Items]
Authorized stock repurchase amount							$ 500,000,000.0	$ 250,000,000.0	$ 150,000,000.0	$ 150,000,000.0	$ 150,000,000.0	$ 150,000,000.0
Stock repurchased during period (in shares) | shares						211,790
Stock repurchased and retired during period, value						$ 27,600,000
Number of days for average common stock repurchase price		20 days
Remaining unused authorization for stock repurchase program						$ 122,400,000			$ 114,600,000		$ 11,900,000
Percent of common stock issued				200.00%
Number of investment banking firms consulting with company | firm				1
Maximum percentage of companies assets, cash flow or earnings power before shareholders will lose right to exercise shares			50.00%
Class of warrant or right, triggering event, repurchase, beneficial owner, percentage			50.00%
Minimum
Distribution Made to Limited Partner [Line Items]
Beneficial ownership percentage			15.00%	15.00%
Series A Preferred Stock | Common Stock
Distribution Made to Limited Partner [Line Items]
Class of warrant or right, issuance rate | right / shares			1	1
Common Stock | Preferred Stock
Distribution Made to Limited Partner [Line Items]
Class of warrant or right, repurchase rate			0.001	0.001
Common Stock | Common Stock
Distribution Made to Limited Partner [Line Items]
Class or warrant or right, percent of common stock issued			200.00%	200.00%
Class of warrant or right, repurchase rate | shares / right			1	1
The Duchossois Group
Distribution Made to Limited Partner [Line Items]
Stock repurchased during period (in shares) | shares	1,000,000	945,000			1,000,000
Stock repurchased and retired during period, value	$ 158,800,000	$ 138,100,000
Repurchase price (in dollars per share) | $ / shares	$ 158.78	$ 146.13
April 2017 Stock Repurchase Program
Distribution Made to Limited Partner [Line Items]
Stock repurchased during period (in shares) | shares					1,077,029
Stock repurchased and retired during period, value					$ 171,700,000
Remaining unused authorization for stock repurchase program					$ 78,300,000