Basis of Presentation and Significant Accounting Policies - Change in Accounting Principle (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lease right-of-use assets	$ 15,074	$ 13,129
Total assets	2,100,859	2,011,280
Accrued expenses	93,140	92,919
Total liabilities and equity	$ 2,100,859	2,011,280
Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lease right-of-use assets		0
Total assets		1,998,151
Accrued expenses		79,790
Total liabilities and equity		1,998,151
Restatement Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lease right-of-use assets		13,129
Total assets		13,129
Accrued expenses		13,129
Total liabilities and equity		$ 13,129