Debt (Credit Agreement) (Details) - Second Amended And Restated Credit Agreement - USD ($)	3 Months Ended
	Mar. 31, 2019	Jul. 31, 2017
Debt Instrument [Line Items]
Credit facility amount		$ 350,000,000
Right to increase credit facility, amount		$ 50,000,000
London Interbank Offered Rate (LIBOR) | Minimum
Debt Instrument [Line Items]
Spread on variable rate basis (as a percent)	1.50%
London Interbank Offered Rate (LIBOR) | Maximum
Debt Instrument [Line Items]
Spread on variable rate basis (as a percent)	3.25%