Income Taxes (Income Tax Expense) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current:
Federal									$ 73,194	$ 97,575	$ 90,542
State and local									5,429	10,970	6,585
Total current									78,623	108,545	97,127
Deferred:
Federal									12,542	(7,279)	(3,784)
State and local									5,158	(8,234)	(1,370)
Total deferred									17,700	(15,513)	(5,154)
Total:
Total federal									85,736	90,296	86,758
Total state and local									10,587	2,736	5,215
Income tax expense	$ 23,845	$ 24,445	$ 24,599	$ 23,434	$ 23,627	$ 24,995	$ 20,426	$ 23,984	$ 96,323	$ 93,032	$ 91,973