Annual report pursuant to Section 13 and 15(d)

Long-Term Debt - Summary of Interest Received and Paid under Term of Cash Flow Swap (Detail)

v3.8.0.1
Long-Term Debt - Summary of Interest Received and Paid under Term of Cash Flow Swap (Detail)
 12 Months Ended
Dec. 31, 2017
USD ($)
Derivatives, Fair Value [Line Items]  
Receive Rate one-month LIBOR
Cash Flow Swap [Member]  
Derivatives, Fair Value [Line Items]  
Notional Amount $ 250,000,000
Pay Rate 1.887%
Receive Rate one-month LIBOR
Maturing Date Jun. 30, 2018
Cash Flow Swap 1 [Member]  
Derivatives, Fair Value [Line Items]  
Notional Amount $ 125,000,000
Pay Rate 1.90%
Receive Rate one-month LIBOR
Maturing Date Jul. 01, 2018
Cash Flow Swap 2 [Member]  
Derivatives, Fair Value [Line Items]  
Notional Amount $ 50,000,000
Pay Rate 2.32%
Receive Rate one-month LIBOR
Maturing Date Jul. 01, 2019
Cash Flow Swap 3 [Member]  
Derivatives, Fair Value [Line Items]  
Notional Amount $ 200,000,000
Pay Rate 2.313%
Receive Rate one-month LIBOR
Maturing Date Jul. 01, 2019
Cash Flow Swap 4 [Member]  
Derivatives, Fair Value [Line Items]  
Notional Amount $ 100,000,000
Pay Rate 1.384%
Receive Rate one-month LIBOR
Maturing Date Jul. 01, 2020
Cash Flow Swap 5 [Member]  
Derivatives, Fair Value [Line Items]  
Notional Amount $ 125,000,000
Pay Rate 1.158%
Receive Rate one-month LIBOR
Maturing Date Jul. 01, 2019
Cash Flow Swap 6 [Member]  
Derivatives, Fair Value [Line Items]  
Notional Amount $ 150,000,000
Pay Rate 1.31%
Receive Rate one-month LIBOR
Maturing Date Jul. 01, 2020
Cash Flow Swap 7 [Member]  
Derivatives, Fair Value [Line Items]  
Notional Amount $ 125,000,000
Pay Rate 1.02%
Receive Rate one-month LIBOR
Maturing Date Jul. 01, 2018
Cash Flow Swap 8 [Member]  
Derivatives, Fair Value [Line Items]  
Notional Amount $ 62,500,000
Pay Rate 2.00%
Receive Rate one-month LIBOR
Maturing Date Jul. 01, 2021
Cash Flow Swap 9 [Member]  
Derivatives, Fair Value [Line Items]  
Notional Amount $ 62,500,000
Pay Rate 2.00%
Receive Rate one-month LIBOR
Maturing Date Jul. 01, 2021
Cash Flow Swap 10 [Member]  
Derivatives, Fair Value [Line Items]  
Notional Amount $ 62,500,000
Pay Rate 2.00%
Receive Rate one-month LIBOR
Maturing Date Jul. 01, 2021
Cash Flow Swap 11 [Member]  
Derivatives, Fair Value [Line Items]  
Notional Amount $ 62,500,000
Pay Rate 2.00%
Receive Rate one-month LIBOR
Maturing Date Jul. 01, 2021