Derivatives and Hedging Activities (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Derivative [Line Items]
Net gain (loss) related to derivative instrument	$ 16,355,000	$ (634,000)
Ineffective portion of the change in fair value derivatives	0
Interest expense	$ 49,230,000	44,636,000
Interest Rate Swaps
Derivative [Line Items]
Weighted average fixed rate	1.844%
Notional amount	$ 1,200,000,000
Interest expense	800,000	$ 2,700,000
Designated as Hedging Instrument | Interest Rate Swaps
Derivative [Line Items]
Fair value of derivative instruments	$ 27,500,000		$ 11,300,000