Supplemental Disclosures of Cash Flow Information and Non-Cash Financing and Investing Activities - Significant Non-Cash Investing and Financing Activities (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
Condensed Cash Flow Statements, Captions [Line Items]
Cash and cash equivalents	$ 546,721,000	$ 401,846,000	$ 515,646,000	$ 443,420,000
Restricted Cash and Cash Equivalents	279,368,000	231,075,000	265,637,000	229,753,000
Cash paid during the period for:
Interest	14,531,000	14,323,000
Income taxes	2,704,000	6,922,000
Significant non-cash investing and financing activities
Other payable issued for purchased customer accounts	0	300,000
Change in estimated acquisition earn-out payables and related charges	(211,000)	606,000
Business Acquisition Cost of Entity Note Payable	0	492,000
Cash and Cash Equivalents inclusive of Restricted Cash [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Cash and cash equivalents	$ 826,089,000	$ 632,921,000	$ 781,283,000	$ 673,173,000