Non-Operating Expense - Additional Information (Details) - USD ($) $ in Millions	1 Months Ended
	Jun. 30, 2016	Dec. 31, 2017
Debt Instrument [Line Items]
Pretax charge on unamortized financing costs of credit facility and deferred expense on related interest rate swaps	$ 0.4
Senior unsecured credit facility- revolving loan due 2021
Debt Instrument [Line Items]
Face value	$ 700.0	$ 700.0
Debt instrument, maturity year	2021