Fair Value - Non-recurring Fair Value Table (Detail) - Non-recurring - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Disposal Group, Held-for-sale, Not Discontinued Operations
Non-Financial Assets and Liabilities:
Assets, fair value disclosure, nonrecurring	$ 0	$ 180,247
Disposal Group, Held-for-sale, Not Discontinued Operations | Level 1
Non-Financial Assets and Liabilities:
Assets, fair value disclosure, nonrecurring	0	0
Disposal Group, Held-for-sale, Not Discontinued Operations | Level 2
Non-Financial Assets and Liabilities:
Assets, fair value disclosure, nonrecurring	0	180,247
Disposal Group, Held-for-sale, Not Discontinued Operations | Level 3
Non-Financial Assets and Liabilities:
Assets, fair value disclosure, nonrecurring	0	0
Property, Plant and Equipment [Member]
Non-Financial Assets and Liabilities:
Assets, fair value disclosure, nonrecurring	0	1,987
Property, Plant and Equipment [Member] | Level 1
Non-Financial Assets and Liabilities:
Assets, fair value disclosure, nonrecurring	0	0
Property, Plant and Equipment [Member] | Level 2
Non-Financial Assets and Liabilities:
Assets, fair value disclosure, nonrecurring	0	0
Property, Plant and Equipment [Member] | Level 3
Non-Financial Assets and Liabilities:
Assets, fair value disclosure, nonrecurring	0	1,987
Real Estate
Non-Financial Assets and Liabilities:
Assets, fair value disclosure, nonrecurring	240	0
Real Estate | Level 1
Non-Financial Assets and Liabilities:
Assets, fair value disclosure, nonrecurring	0	0
Real Estate | Level 2
Non-Financial Assets and Liabilities:
Assets, fair value disclosure, nonrecurring	240	0
Real Estate | Level 3
Non-Financial Assets and Liabilities:
Assets, fair value disclosure, nonrecurring	$ 0	$ 0