Benefit Plans - Additional Information (Detail) (USD $)	3 Months Ended	6 Months Ended	12 Months Ended						12 Months Ended												0 Months Ended				12 Months Ended
	Jun. 30, 2013	Jun. 30, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Maximum [Member]	Dec. 31, 2013 Non-qualified plans for former directors [Member]	Dec. 31, 2012 Non-qualified plans for former directors [Member]	Dec. 31, 2013 Funded plans for former directors [Member]	Dec. 31, 2012 Funded plans for former directors [Member]	Dec. 31, 2012 Zero Percent Yielding Freddie Mac and Fannie Mae Perpetual Preferred Stock [Member]	Dec. 31, 2013 Stock Options [Member]	Dec. 31, 2012 Stock Options [Member]	Dec. 31, 2011 Stock Options [Member]	Dec. 31, 2013 Stock Options and Restricted Stock [Member]	Dec. 31, 2012 Stock Options and Restricted Stock [Member]	Dec. 31, 2011 Stock Options and Restricted Stock [Member]	Dec. 31, 2013 Restricted Stock [Member]	Dec. 31, 2012 Restricted Stock [Member]	Dec. 31, 2011 Restricted Stock [Member]	Jan. 29, 2014 Subsequent event [Member] Director Restricted Stock Plan [Member]	Dec. 31, 2013 Other Pension Plan, Defined Benefit [Member]	Jun. 30, 2013 Other Pension Plan, Defined Benefit [Member]	Dec. 31, 2012 Other Pension Plan, Defined Benefit [Member]	Dec. 31, 2013 Equity securities [Member]	Dec. 31, 2013 Equity securities [Member] Consumer Price Index [Member]	Dec. 31, 2013 Equity securities [Member] S&P 500 Index [Member]	Dec. 31, 2013 Debt securities [Member]	Dec. 31, 2013 Fixed income securities [Member]	Dec. 31, 2013 Fixed income securities [Member] Consumer Price Index [Member]	Dec. 31, 2013 Fixed income securities [Member] Merrill Lynch Intermediate Government/Corporate Index [Member]	Dec. 31, 2012 Trust Preferred Securities Subject to Mandatory Redemption [Member]
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Decrease in projected benefit obligations	$ (22,900,000)	$ (22,900,000)
Decrease in accumulated other comprehensive loss, net of tax		(19,900,000)
Discount rate used to compute the obligation				4.87%	5.75%	4.87%																4.89%	4.87%	4.26%
Expected rate of return on plan assets		7.50%	7.50%	7.50%	8.00%
Curtailment loss	(750,000)		(750,000)
Net actuarial loss expected to be recognized as a component of net periodic pension expense			243,000
Target asset allocation for qualified plan, minimum																									25.00%			35.00%
Target asset allocation for qualified plan, maximum																									65.00%			75.00%
Cumulative annual real return																									7.00%				3.00%
Cumulative annual real return, period																										5 years	3 years			5 years	3 years
Preferred securities											58,631
Shares, fair values																																1,500,000
Dividends received on preferred shares											114,000
Projected benefit obligation			145,034,000	144,390,000			5,000,000	5,800,000	2,700,000	3,300,000
Obligation included in other comprehensive loss, net of tax									1,300,000	1,400,000
Obligation included in other comprehensive loss, tax									965,000	1,000,000
Salary expense			6,000,000	7,400,000	4,000,000
Expense for contributions to savings and investment plan			2,600,000	2,700,000	2,000,000
Percentage increase in contribution			6.00%
Number of shares authorized under stock incentive plan			7,400,000
Incentive stock option's maximum term, years						10 years
Stock-based compensation expense			6,055,000	4,816,000	3,156,000										6,000,000	4,700,000	3,300,000
Stock awards granted															2,700,000	2,500,000
Stock awards granted												0	0	0			0
Stock-based compensation			9,300,000
Average remaining vesting, years			4 years
Compensation costs related to restricted stock awards																		6,000,000	4,600,000	2,900,000
Additional fees																					$ 0