Supplemental Disclosures of Cash Flow Information and Non-Cash Financing and Investing Activities - Significant Non-Cash Investing and Financing Activities (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted Cash and Cash Equivalents	$ 338,635,000	$ 250,705,000	$ 265,637,000
Cash and Cash Equivalents, at Carrying Value	438,961,000	573,383,000	515,646,000
Cash paid during the period for:
Interest	38,032,000	36,172,000	37,652,000
Income taxes	110,557,000	152,024,000	143,111,000
Significant non-cash investing and financing activities
Other payables issued for purchased customer accounts	5,462,000	11,708,000	10,664,000
Estimated acquisition earn-out payables and related charges	77,378,000	6,921,000	4,463,000
Notes Assumed	0	0	492,000
Notes received on the sale of fixed assets and customer accounts	52,000	0	22,000
Cash and Cash Equivalents inclusive of Restricted Cash [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and Cash Equivalents, at Carrying Value	$ 777,596,000	$ 824,088,000	$ 781,283,000