Recent Accounting Developments - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
U.S. federal statutory income tax rate	21.00%	35.00%	35.00%
Minimum [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Right-of-use asset and lease liabilities	$ 500,000,000
Maximum [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Right-of-use asset and lease liabilities	600,000,000
Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Effect of reclassification of amounts previously classified as an expense to revenue	93,831,000
Effect of reclassification of costs from revenue to operating expenses	$ 93,831,000