Income Taxes - Components of Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013
Income Tax Disclosure [Abstract]
Income tax expense from continuing operations	$ 249,894	$ 256,603	[1]	$ 248,110	[1]
Shareholders’ equity:
Other comprehensive income (loss)	(411,646)	424,089		(386,752)
Tax basis compensation expense (from the exercise of stock options and vesting of restricted stock awards) in excess of amounts recognized for financial reporting purposes	(17,577)	(18,524)		(21,314)
Income tax expense	$ (179,329)	$ 662,168		$ (159,956)

[1] Certain balances were adjusted to give effect to discontinued operations and the adoption of new accounting guidance as described in Note 1- Significant Accounting Policies under the caption "Low-Income Housing Tax Credit Interests."