Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities:
Net income	$ 58,024	$ 21,850	$ 47,129
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	7,660	7,269	6,204
Bad debt provision	4,335	4,470	1,990
Deferred income tax (benefit) expense	17,842	(15,059)	(4,922)
Stock-based compensation expense	3,541	3,080	2,607
Tax benefit from equity compensation plans	(1,873)	(2,626)	(2,615)
Amortization of premium on marketable securities	681	354	537
Unrealized (gain) loss on deferred compensation fund investments	24	(1,216)	(2,820)
Changes in operating assets and liabilities:
Accounts and notes receivable	(18,854)	(13,492)	(50,879)
Inventories and supplies	(846)	(3,015)	(3,772)
Prepaid expenses and other assets	(1,710)	(417)	790
Notes receivable — long term	0	600	(3,956)
Deferred compensation funding	(649)	(2,542)	(4,369)
Accounts payable and other accrued expenses	2,403	492	25,961
Accrued payroll, accrued and withheld payroll taxes	(28,314)	11,813	6,349
Accrued insurance claims	13,987	42,084	3,616
Deferred compensation liability	1,113	4,248	7,721
Income taxes payable	5,997	(163)	2,587
Net cash provided by operating activities	63,361	57,730	32,158
Cash flows from investing activities:
Disposals of fixed assets	267	83	158
Additions to property and equipment	(4,998)	(5,795)	(3,762)
Purchases of marketable securities	(75,150)	(5,140)	(6,598)
Sales of marketable securities	17,567	4,392	15,807
Cash paid for acquisition	0	0	(5,000)
Net cash (used in) provided by investing activities	(62,314)	(6,460)	605
Cash flows from financing activities:
Dividends paid	(51,375)	(49,077)	(46,707)
Reissuance of treasury stock pursuant to Dividend Reinvestment Plan	113	110	107
Tax benefit from equity compensation plans	1,873	2,626	2,615
Proceeds from the exercise of stock options	6,251	6,196	6,428
Net cash used in financing activities	(43,138)	(40,145)	(37,557)
Net change in cash and cash equivalents	(42,091)	11,125	(4,794)
Cash and cash equivalents at beginning of the period	75,280	64,155	68,949
Cash and cash equivalents at end of the period	33,189	75,280	64,155
Supplementary Cash Flow Information:
Cash paid for interest	258	156	4
Cash paid for income taxes, net of refunds	$ 7,901	$ 25,080	$ 21,694