Income Taxes (Schedule of Effective Income Tax Rate Reconciliation) (Details) - USD ($)
$ in Thousands

3 Months Ended

12 Months Ended

Dec. 31, 2016

Dec. 31, 2016

Dec. 31, 2015

Dec. 31, 2014

Income Tax Disclosure [Abstract]

Statutory federal income tax rate

35.00%

Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation [Abstract]

Computed “expected” tax expense

$ 313,753

$ 256,210

$ 333,269

Tax-exempt investment income

(37,379)

(39,283)

(38,757)

Change in valuation allowance

1,420

2,702

1,335

Impact of foreign tax rates

1,984

4,447

6,239

State and local taxes

7,748

940

2,375

Other, net

5,427

2,907

(1,868)

Total expense

$ (302,593)

$ 292,953

$ 227,923

$ 302,593

Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]

A reconciliation of the income tax expense and the amounts computed by applying the Federal and foreign income tax rate of 35% to pre-tax income are as follows:

(In thousands)	2016			2015			2014
Computed “expected” tax expense	$	313,753		$	256,210		$	333,269
Tax-exempt investment income	(37,379		)	(39,283		)	(38,757		)
Change in valuation allowance	1,420			2,702			1,335
Impact of foreign tax rates	1,984			4,447			6,239
State and local taxes	7,748			940			2,375
Other, net	5,427			2,907			(1,868		)
Total expense	$	292,953		$	227,923		$	302,593

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