Supplemental Guarantor Condensed Consolidated Financial Statements - Condensed Consolidating Statements of Cash Flows (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash flows from operations:
Net income (loss) for the period	$ 3,893	$ (3,883)
Adjustments to reconcile net income (loss) to net cash used in operating activities:
Depreciation and amortization	2,514	2,845
Deferred income tax	14,560	(6,666)
Amortization of notes receivable	4,739	4,870
Amortization of debt issuance costs	160	99
Amortization of intangible assets		3,212
Provision for credit losses	(17)	178
Share-based compensation expense	1,879	1,259
Changes in operating assets and liabilities	(133,399)	(42,817)
Cash used in operating activities	(105,671)	(40,903)
Cash flows from Investment activities
Purchase of office facilities	(5,120)	(4,711)
Cash used in investing activities	(5,120)	(4,711)
Cash flows from financing activities
Cash dividends paid on Class A non-voting and Class B voting common stock	(1,497)	(1,495)
Repurchase of Class A non-voting common stock		(1,551)
Other financing activities	75,700	65,141
Cash provided by financing activities	74,203	62,095
Net increase (decrease) in cash and cash equivalents	(36,588)	16,481
Cash and cash equivalents, beginning of period	135,366	70,329
Cash and cash equivalents, end of period	98,778	86,810
Parent [Member]
Cash flows from operations:
Net income (loss) for the period	(3,239)	(3,013)
Adjustments to reconcile net income (loss) to net cash used in operating activities:
Amortization of debt issuance costs	160
Changes in operating assets and liabilities	4,581	4,130
Cash used in operating activities	1,502	1,117
Cash flows from financing activities
Cash dividends paid on Class A non-voting and Class B voting common stock	(1,497)	(1,495)
Repurchase of Class A non-voting common stock		(1,551)
Other financing activities		41
Cash provided by financing activities	(1,497)	(3,005)
Net increase (decrease) in cash and cash equivalents	5	(1,888)
Cash and cash equivalents, beginning of period	35	2,555
Cash and cash equivalents, end of period	40	667
Guarantor subsidiaries [Member]
Cash flows from operations:
Net income (loss) for the period	2,221	2,310
Adjustments to reconcile net income (loss) to net cash used in operating activities:
Changes in operating assets and liabilities	(11,485)	18,008
Cash used in operating activities	(9,264)	20,318
Cash flows from financing activities
Net increase (decrease) in cash and cash equivalents	(9,264)	20,318
Cash and cash equivalents, beginning of period	40,658	11,882
Cash and cash equivalents, end of period	31,394	32,200
Non-guarantor Subsidiaries [Member]
Cash flows from operations:
Net income (loss) for the period	4,911	(3,180)
Adjustments to reconcile net income (loss) to net cash used in operating activities:
Depreciation and amortization	2,514	2,845
Deferred income tax	14,560	(6,666)
Amortization of notes receivable	4,739	4,870
Amortization of debt issuance costs		99
Amortization of intangible assets		3,212
Provision for credit losses	(17)	178
Share-based compensation expense	1,879	1,259
Changes in operating assets and liabilities	(126,495)	(64,955)
Cash used in operating activities	(97,909)	(62,338)
Cash flows from Investment activities
Purchase of office facilities	(5,120)	(4,711)
Cash used in investing activities	(5,120)	(4,711)
Cash flows from financing activities
Other financing activities	75,700	65,100
Cash provided by financing activities	75,700	65,100
Net increase (decrease) in cash and cash equivalents	(27,329)	(1,949)
Cash and cash equivalents, beginning of period	94,673	55,892
Cash and cash equivalents, end of period	$ 67,344	$ 53,943