Stock Options and Incentive Plans (Narrative) (Details) (USD $)	1 Months Ended			12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Incentive and deferred compensation				$ 4,960,000	$ 2,087,000
Prosperity Plus Savings Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred compensation plan expense				4,100,000	3,800,000	3,700,000
Maximum percent of annual compensation which the Company can match				5.00%
Prosperity Plus Savings Plan [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee contribution, percent				1.00%
Percent of employee contribution matched by the Company				50.00%
Prosperity Plus Savings Plan [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee contribution, percent				15.00%
Percent of employee contribution matched by the Company				100.00%
Profit Sharing Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred compensation plan expense				1,600,000	1,800,000	2,300,000
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contractual term of stock options, in years				20 years
Length of time options are valid after retirement, in years				10 years
Aggregate intrinsic value of vested options				3,900,000
Aggregate intrinsic value of options exercised				3,100,000	200,000	300,000
Long Term Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of stock authorized for payment of awards				339,050
Shares issued for long term incentive plan	40,255	6,727	32,177
Cash payments in connection with long term incentive plan	1,100,000	200,000	800,000
Deferred compensation expense				2,400,000	2,400,000	2,400,000
Long Term Incentive Plan [Member] | Management [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Earned incentive compensation paid in shares of Class A Common Stock				40.00%
Shares issued for long term incentive plan	34,988	27,768
Cash payments in connection with long term incentive plan	2,000,000	1,500,000
Deferred compensation expense				3,400,000	3,400,000	2,700,000
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred compensation expense				2,500,000	1,900,000	2,500,000
Vesting period				5 years
Restricted Stock [Member] | Management [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred compensation expense					500,000	1,300,000
Additional Restricted Stock Plan [Member] | Management [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred compensation expense				1,000,000	400,000
Phantom Stock Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred compensation expense				$ 1,500,000	$ 500,000
Vesting period				5 years