Shareholders' Equity (Details)			12 Months Ended
	Nov. 19, 2015 USD ($) $ / shares shares	Mar. 13, 2008 right / shares shares / right firm	Dec. 31, 2014 USD ($) shares	Feb. 24, 2016 USD ($)	Dec. 31, 2015 USD ($)	Oct. 28, 2015 USD ($)	Apr. 23, 2013 USD ($)
Authorized stock repurchase amount					$ 150,000,000.0	$ 150,000,000	$ 100,000,000
Stock Repurchased During Period (in shares) | shares			691,000
Stock Repurchased and Retired During Period, Value			$ 61,600,000
Number of days for average common stock repurchase price	20 days
Remaining unused authorization for stock repurchase program					$ 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
Beneficial ownership percentage		15.00%
Common Stock | Common Stock
Class or Warrant or Right, Percent of Common Stock Issued		200.00%
Class of Warrant or Right, Repurchase Rate | shares / right		1
Common Stock | Series A Preferred Stock
Class of Warrant or Right, Repurchase Rate | shares / right		0.0001
Series A Preferred Stock | Common Stock
Class of Warrant or Right, Issuance Rate | right / shares		1
The Duchossois Group
Stock Repurchased During Period (in shares) | shares	945,000
Stock Repurchased and Retired During Period, Value	$ 138,100,000
Repurchase price (in dollars per share) | $ / shares	$ 146.13
Subsequent Event
Authorized stock repurchase amount				$ 150,000,000.0