Discontinued Operations - Additional Information (Detail) - USD ($)		3 Months Ended			9 Months Ended
	Jan. 09, 2015	Sep. 30, 2015	Jun. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	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	$ 100,000
Repurchase claims received or settled		$ 0			$ 0		$ 0
Repurchase reserve		700,000			700,000		$ 5,500,000
Recovery of allowance for repurchase reserve					$ 4,800,000	$ 700,000
Decrease in allowance for repurchase reserve		$ 0		$ 200,000
Increase in earnings from discontinued operations per share					$ 0.17
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			$ 4,300,000		$ 4,300,000