Long-term Obligations - Revolving Credit Facility (Details)	1 Months Ended		9 Months Ended
	Feb. 28, 2017 USD ($)	Oct. 31, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)
Line of Credit Facility [Line Items]
Proceeds from lines of credit		$ 300,000,000
Repayments of lines of credit	$ 300,000,000		$ 300,000,000	$ 0
Line of credit facility additional borrowing capacity		300,000,000.0
Line of Credit
Line of Credit Facility [Line Items]
Line of credit facility, current borrowing capacity		$ 500,000,000.0
Debt covenant, consolidated leverage ratio		3.00
Debt covenant, minimum consolidated EBITDA		$ 200,000,000.0
Base Rate | Minimum | Line of Credit
Line of Credit Facility [Line Items]
Interest rate, stated percentage		0.75%
Base Rate | Maximum | Line of Credit
Line of Credit Facility [Line Items]
Interest rate, stated percentage		1.50%
Eurodollar | Minimum | Line of Credit
Line of Credit Facility [Line Items]
Interest rate, stated percentage		1.75%
Eurodollar | Maximum | Line of Credit
Line of Credit Facility [Line Items]
Interest rate, stated percentage		2.50%