Notes Payable, Other and Short-term Borrowings - Carrying Amounts and Estimated Fair Values of Company's Senior Notes (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Carrying amount of the Company's long-term debt	$ 945,652	$ 946,930
Estimated fair value of the Company's long-term debt	973,605	992,250
8.125% Senior Notes [Member]
Debt Instrument [Line Items]
Carrying amount of the Company's long-term debt	109,459	109,396
Estimated fair value of the Company's long-term debt	115,695	116,550
5.375% Senior Notes [Member]
Debt Instrument [Line Items]
Carrying amount of the Company's long-term debt	298,555	298,064
Estimated fair value of the Company's long-term debt	307,290	313,125
8.375% Senior Notes [Member]
Debt Instrument [Line Items]
Carrying amount of the Company's long-term debt	240,235	242,474
Estimated fair value of the Company's long-term debt	240,180	247,200
5.125% Senior Notes [Member]
Debt Instrument [Line Items]
Carrying amount of the Company's long-term debt	297,403	296,996
Estimated fair value of the Company's long-term debt	$ 310,440	$ 315,375