Income Taxes (Income Tax Expense) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Current:
Federal									$ 98,442	$ 90,542	$ 62,042
State and local									11,047	6,585	3,572
Total current									109,489	97,127	65,614
Deferred:
Federal									(7,279)	(3,784)	10,760
State and local									(8,234)	(1,370)	739
Total deferred									(15,513)	(5,154)	11,499
Total:
Total federal									91,163	86,758	72,802
Total state and local									2,813	5,215	4,311
Income tax expense	$ 24,146	$ 25,075	$ 20,663	$ 24,092	$ 23,753	$ 23,824	$ 23,159	$ 21,237	$ 93,976	$ 91,973	$ 77,113