Fair Value Measurements - Schedule of Fair Values of Financial Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	$ 29,039	$ 22,393
Interest rate swap assets (included in "other assets")	9,855	139
Total assets	38,894	22,532
Interest rate swap liabilities (included in "other liabilities")	317	22,446
Total liabilities	317	22,446
Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	29,039	22,393
Total assets	29,039	22,393
Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Interest rate swap assets (included in "other assets")	9,855	139
Total assets	9,855	139
Interest rate swap liabilities (included in "other liabilities")	317	22,446
Total liabilities	$ 317	$ 22,446