Discontinued Operations - Statement of Income (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Discontinued Operations and Disposal Groups [Abstract]
Revenues		$ 0	$ 395,070,000
Transaction expenses from discontinued operations	$ 0	(9,043,000)	0
Gain on sale of discontinued operations	0	80,205,000	0
Pre-tax income from discontinued operations		71,162,000	61,786,000
Income tax expense from discontinued operations	0	(13,103,000)	(19,884,000)
Net income from discontinued operations	0	58,059,000	$ 41,902,000
Assets of discontinued operations	0	0
Liabilities of discontinued operations	$ 0	$ 0