Annual report pursuant to Section 13 and 15(d)

Soft Dollar Arrangements - Additional Information (Detail)

v2.4.1.9
Soft Dollar Arrangements - Additional Information (Detail) (USD $)
In Thousands, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Soft Dollar Arrangements [Abstract]      
Soft dollar credits $ 1,053samg_SoftDollarCredits $ 992samg_SoftDollarCredits $ 320samg_SoftDollarCredits