Discontinued Operations - Additional Information (Detail) - USD ($)		3 Months Ended	6 Months Ended
	Jan. 09, 2015	Jun. 30, 2015	Jun. 30, 2015	Jun. 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	$ 78,000,000
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	$ 500,000
Decrease in allowance for repurchase reserve		$ 4,600,000	$ 200,000
Increase in earnings from discontinued operations per share		$ 0.15	$ 0.17
Gain on sale of NABCO			$ 39,700,000
ACE Securities [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Recovery of allowance for repurchase reserve			$ 4,300,000