Other Comprehensive Income (Loss) - Summary of Accumulated Other Comprehensive Income (Loss) Balances, Net of Tax (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Jan. 11, 2013
Equity [Abstract]
Unrealized gain (loss) on securities available for sale, Beginning Balance	$ (43,364)		$ 5,082
Unrealized gain (loss) on securities available for sale, Current Period Change	12,568	(2,963)
Unrealized gain (loss) on securities available for sale, Ending Balance	(30,796)	2,119	5,082
Unrealized gains on post-retirement benefits, Beginning Balance	1,699		1,600
Unrealized gains on post-retirement benefits, Current Period Change
Unrealized gains on post-retirement benefits, Ending Balance	1,699	1,600	1,600
Total, Beginning Balance	(41,665)		6,682
Total, Current Period Change	12,568	(2,963)
Total, Ending Balance	$ (29,097)	$ 3,719	$ 6,682