Summary of Significant Accounting Policies - Balances of Financial Instruments Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands |
Dec. 31, 2017 |
Dec. 31, 2016 |
|---|---|---|
| Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] | ||
| Interest rate swap, assets | $ 11,008 | $ 9,598 |
| Interest rate swap, liabilities | (5,020) | (10,217) |
| Fair Value, Measurements, Recurring | ||
| Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] | ||
| Interest rate swap, assets | 11,008 | 9,598 |
| Interest rate swap, liabilities | (5,020) | (10,217) |
| Interest rate derivatives, at fair value, net | 5,988 | (619) |
| Fair Value, Measurements, Recurring | Level 2 | ||
| Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] | ||
| Interest rate swap, assets | 11,008 | 9,598 |
| Interest rate swap, liabilities | (5,020) | (10,217) |
| Interest rate derivatives, at fair value, net | $ 5,988 | $ (619) |