Condensed Consolidated Balance Sheets (Unaudited) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Current assets:
Cash	$ 81,101	$ 112,182
Accounts receivable, less allowance of $1,745 in 2013 and $1,444 in 2012	76,280	75,262
Other current assets	19,900	10,952
Total current assets	177,281	198,396
Property and equipment	266,811	239,138
Less accumulated depreciation and amortization	109,346	105,581
Total property and equipment, net	157,465	133,557
Goodwill and other acquired intangibles:
Goodwill	87,771	43,332
Other acquired intangibles, net of accumulated amortization of $28,763 in 2013 and $26,028 in 2012	43,138	22,102
Total net goodwill and other acquired intangibles	130,909	65,434
Other assets	2,537	1,800
Total assets	468,192	399,187
Current liabilities:
Accounts payable	12,189	11,168
Accrued expenses	17,220	16,476
Current portion of debt and capital lease obligations	121	276
Total current liabilities	29,530	27,920
Long-term debt and capital lease obligations, less current portion	23	58
Other long-term liabilities	8,985	7,098
Deferred income taxes	25,899	12,440
Shareholders' equity:
Preferred stock	0	0
Common stock, $0.01 par value: Authorized shares - 50,000,000, Issued and outstanding shares - 30,346,233 in 2013 and 29,194,761 in 2012	303	292
Additional paid-in capital	98,915	64,644
Retained earnings	304,537	286,735
Total shareholders' equity	403,755	351,671
Total liabilities and shareholders' equity	$ 468,192	$ 399,187