Long-Term Debt - 7.25 Senior Notes (Details) - USD ($)		12 Months Ended
	Dec. 04, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Long-Term Debt
Principle amount of senior notes	$ 350,000,000.0
Repayments of long-term debt		$ 675,000,000	$ 1,921,758,000	$ 1,727,500,000
Amortization of debt discount		1,245,000	$ 1,170,000	$ 12,380,000
7.25% senior notes due December 2018
Long-Term Debt
Principle amount of senior notes	$ 350,000,000.0
Interest rate (as a percent)	7.25%
Repayments of long-term debt	$ 369,200,000
Call premium expense		6,300,000
Amortization of debt discount		$ 2,900,000
7.25% senior notes due December 2018 | Twelve month period beginning December 1, 2015
Long-Term Debt
Redemption price as percentage of principal amount	101.813%