Deferred Sales Commissions, Net (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Gross to net deferred sales commissions [Abstract]
Carrying amount of deferred sales commissions	$ 660,735	[1]	$ 624,995	[1]
Less: Accumulated amortization	(434,770)	[1]	(397,095)	[1]
Cumulative CDSC received	(165,966)	[1]	(151,744)	[1]
Deferred sales commissions, net	59,999	[1]	76,156	[1]
Amortization expense	37,675		47,397		54,922
Estimated future amortization of deferred sales commissions [Abstract]
2012	26,361
2013	17,646
2014	11,007
2015	4,245
2016	651
2017	89
Total	$ 59,999

[1] Excludes amounts related to fully amortized deferred sales commissions