Income Taxes - Additional Information (Detail) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Income Taxes [Line Items]
Total income tax expense (benefit), rate	24.40%	27.80%
Combined federal and state statutory tax rate	37.20%
Federal deferred tax asset	$ 88,000,000	$ 148,000,000	$ 174,000,000
State deferred tax asset	13,000,000	4,000,000	20,000,000
Valuation allowance		1,000,000
Reduction in deferred tax assets	1,000,000	1,000,000	1,000,000
Maximum [Member]
Income Taxes [Line Items]
Valuation allowance	$ 1,000,000		$ 1,000,000