Derivative and Other Fair Value Instruments - Summary of Consolidated Derivative Instruments (Parenthetical) (Details)	12 Months Ended
	Dec. 31, 2017 USD ($)
Derivative [Line Items]
Debt instrument, maturity date	Jan. 10, 2022
Forward Starting Swaps [Member]
Derivative [Line Items]
Current Notional Balance	$ 250,000,000
Forward Starting Swaps Mandatory Counterparty Terminations in 2019 [Member]
Derivative [Line Items]
Current Notional Balance	200,000,000
Forward Starting Swaps Mandatory Counterparty Terminations in 2020 [Member]
Derivative [Line Items]
Current Notional Balance	50,000,000
2.375% Notes [Member]
Derivative [Line Items]
Proceeds from issuance of unsecured debt	$ 450,000,000
Interest Rate Ranges	2.375%
Debt instrument, maturity date	Jul. 01, 2019
Debt instrument, basis spread on variable rate	0.61%
2.375% Notes [Member] | London Interbank Offered Rate (LIBOR) [Member]
Derivative [Line Items]
Debt instrument, description of variable rate basis	0