Consolidated Statements of Changes in Stockholder's Equity (USD $) In Thousands, unless otherwise specified	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Less: Treasury Common Stock	Less: Treasury Preferred Stock	Less: Unearned Employee Stock Ownership Plan Shares
Balance at Mar. 31, 2010	$ 812,911	$ 10,497	$ 421,996	$ (56,207)	$ 969,017	$ (525,653)	$ (2,185)	$ (4,554)
Consolidated statement of change in equity
Increase in market value of released ESOP shares	3,038	0	3,038	0	0	0	0	0
Release of unearned ESOP Shares	1,172	0	0	0	0	0	0	1,172
Foreign currency translation	3,114	0	0	3,114	0	0	0	0
Unrealized gain on investments, net of tax	4,930	0	0	4,930	0	0	0	0
Fair market value of cash flow hedges, net of tax	1,495	0	0	1,495	0	0	0	0
Adjustment of postretirement benefit obligation	201	0	0	201	0	0	0	0
Net earnings	183,575	0	0	0	183,575	0	0	0
Less: Excess of redemption value over carrying value of preferred shares redeemed	(178)	0	0	0	(178)	0	0	0
Preferred stock dividends paid	(12,412)	0	0	0	(12,412)	0	0	0
Redemption of preferred shares	(5,004)	0	0	0	0	0	(5,004)	0
Contribution from related party	178	0	178	0	0	0	0	0
Net activity	180,109	0	3,216	9,740	170,985	0	(5,004)	1,172
Balance at Mar. 31, 2011	993,020	10,497	425,212	(46,467)	1,140,002	(525,653)	(7,189)	(3,382)
Consolidated statement of change in equity
Increase in market value of released ESOP shares	3,141	0	3,141	0	0	0	0	0
Release of unearned ESOP Shares	984	0	0	0	0	0	0	984
Foreign currency translation	(2,854)	0	0	(2,854)	0	0	0	0
Unrealized gain on investments, net of tax	10,005	0	0	10,005	0	0	0	0
Fair market value of cash flow hedges, net of tax	(5,691)	0	0	(5,691)	0	0	0	0
Adjustment of postretirement benefit obligation	(429)	0	0	(429)	0	0	0	0
Net earnings	205,367	0	0	0	205,367	0	0	0
Less: Excess of redemption value over carrying value of preferred shares redeemed	(5,908)	0	0	0	(5,908)	0	0	0
Preferred stock dividends paid	(2,913)	0	0	0	(2,913)	0	0	0
Common stock dividends	(19,484)	0	0	0	(19,484)	0	0	0
Redemption of preferred shares	(144,808)	0	0	0	0	0	(144,808)	0
Contribution from related party	5,390	0	5,390	0	0	0	0	0
Net activity	42,800	0	8,531	1,031	177,062	0	(144,808)	984
Balance at Mar. 31, 2012	1,035,820	10,497	433,743	(45,436)	1,317,064	(525,653)	(151,997)	(2,398)
Consolidated statement of change in equity
Adjustment to initially apply ASU 2010-26	(1,721)	0	0	0	(1,721)	0	0	0
Increase in market value of released ESOP shares	4,425	0	4,425	0	0	0	0	0
Release of unearned ESOP Shares	692	0	0	0	0	0	0	692
Foreign currency translation	(1,271)	0	0	(1,271)	0	0	0	0
Unrealized gain on investments, net of tax	18,779	0	0	18,779	0	0	0	0
Fair market value of cash flow hedges, net of tax	5,831	0	0	5,831	0	0	0	0
Adjustment of postretirement benefit obligation	(583)	0	0	(583)	0	0	0	0
Net earnings	264,708	0	0	0	264,708	0	0	0
Common stock dividends	(97,421)	0	0	0	(97,421)	0	0	0
Net activity	193,439	0	4,425	22,756	165,566	0	0	692
Balance at Mar. 31, 2013	$ 1,229,259	$ 10,497	$ 438,168	$ (22,680)	$ 1,482,630	$ (525,653)	$ (151,997)	$ (1,706)