Discontinued Operations - Additional Information (Detail) - USD ($)		12 Months Ended
	Jan. 09, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Gross proceeds from sale of wholly owned subsidiary	$ 77,900,000
Payment for final working capital adjustment from buyer	$ 100,000
Repurchase claims received or settled		$ 0	$ 0
Repurchase reserve		0	700,000
Recovery of allowance for repurchase reserve		700,000	4,800,000
Decrease in allowance for repurchase reserve				$ 1,000,000
Gain on sale of NABCO			39,700,000
A C E Securities
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Recovery of allowance for repurchase reserve		$ 700,000	$ 4,800,000