Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 9,071	$ 11,345
Accounts receivable, net of allowances of $5,120 and $4,209, respectively	290,865	284,379
Deferred income taxes	7,542	8,607
Prepaid expenses and other current assets	52,996	46,658
Total current assets	360,474	350,989
Property and equipment, net of accumulated depreciation of $61,732 and $47,629, respectively	188,025	146,850
Other assets:
Goodwill	686,987	669,652
Intangible assets, net	80,239	79,878
Other noncurrent assets	13,633	10,451
Total other assets	780,859	759,981
Total assets	1,329,358	1,257,820
Current liabilities:
Current maturities of long-term debt	15,000	10,000
Accounts payable	110,242	118,743
Accrued expenses and other liabilities	44,813	42,352
Total current liabilities	170,055	171,095
Long-term debt, net of current maturities	443,000	420,000
Other long-term liabilities	115,586	107,950
Total liabilities	728,641	699,045
Stockholders' Equity Attributable to Parent [Abstract]
Common stock $.01 par value; 100,000 shares authorized; 38,266 and 37,925 shares issued and outstanding	383	379
Additional paid-in capital	396,797	390,725
Retained earnings	203,537	167,671
Total stockholders’ investment	600,717	558,775
Total liabilities and stockholders’ investment	$ 1,329,358	$ 1,257,820