Credit Facility (Details)	3 Months Ended	6 Months Ended
	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($) Option	Dec. 31, 2015 USD ($)
Line of Credit Facility [Line Items]
Maximum capacity on credit facility		$ 705,000,000
Options To Extend Maturity Of Credit Facility | Option		2
Additional borrowing capacity under certain circumstances		$ 1,000,000,000
Credit facility		485,000,000	$ 485,000,000
Term Loan
Line of Credit Facility [Line Items]
Maximum capacity on credit facility		305,000,000
Credit facility		305,000,000	305,000,000
Revolving Loan
Line of Credit Facility [Line Items]
Maximum capacity on credit facility		400,000,000
Credit facility		$ 180,000,000	$ 180,000,000
Credit Facility
Line of Credit Facility [Line Items]
Effective interest rate		2.59%	2.39%
Remaining borrowing capacity		$ 56,800,000
Credit Facility | LIBOR
Line of Credit Facility [Line Items]
Unused capacity commitment fee percentage threshold		50.00%
Credit Facility | Line of Credit Facility, Interest Rate, Option One | Minimum | LIBOR
Line of Credit Facility [Line Items]
Spread on variable rate basis		1.50%
Credit Facility | Line of Credit Facility, Interest Rate, Option One | Maximum | LIBOR
Line of Credit Facility [Line Items]
Spread on variable rate basis		2.25%
Credit Facility | Line of Credit Facility, Interest Rate, Option Two | Minimum | Base Rate
Line of Credit Facility [Line Items]
Spread on variable rate basis		0.50%
Credit Facility | Line of Credit Facility, Interest Rate, Option Two | Maximum | Base Rate
Line of Credit Facility [Line Items]
Spread on variable rate basis		1.25%
Credit Facility | Line of Credit Facility, Base Rate, Option Two | Federal Funds Effective Rate
Line of Credit Facility [Line Items]
Spread on variable rate basis		0.50%
Credit Facility | Line of Credit Facility, Base Rate, Option Three | One-Month LIBOR
Line of Credit Facility [Line Items]
Spread on variable rate basis		1.00%
Credit Facility | Below Threshold | LIBOR
Line of Credit Facility [Line Items]
Unused capacity fee percentage		0.15%
Credit Facility | Above Threshold | LIBOR
Line of Credit Facility [Line Items]
Unused capacity fee percentage		0.25%
Interest Expense
Line of Credit Facility [Line Items]
Error (understatement), amount	$ (300,000)
Net Loss
Line of Credit Facility [Line Items]
Error (understatement), amount	$ (600,000)