Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands		12 Months Ended
	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes [Line Items]
(Losses) earnings before Income Taxes, Domestic		$ (132,700)	$ 407,700	$ 376,700
(Losses) earnings before Income Taxes, Foreign		169,400	240,100	380,700
Income tax expense		$ (63,802)	$ 187,141	$ 195,173
Statutory federal income tax rate		35.00%	35.00%	35.00%
State net operating loss carry forward		$ 18,300	$ 25,200
Valuation allowance		18,300	25,200
Annual limitation on the use of foreign tax credit carryforwards and minimum tax credit carryforwards by Transatlantic		42,700
Interest or penalties accrued for uncertain tax positions		$ 0
Subsequent Event
Income Taxes [Line Items]
Statutory federal income tax rate	21.00%
Prior Period Adjustments
Income Taxes [Line Items]
Income tax expense			$ 16,100