Restructuring plan (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Restructuring Cost And Reserve [Line Items]
Restructuring Charges					$ 26,700
Segment, Continuing Operations [Member]
Restructuring Cost And Reserve [Line Items]
Personnel costs	$ 120,977	$ 99,100	$ 237,435	$ 203,401
Net occupancy expenses	23,286	20,267	44,995	41,627
Equipment Expense	15,925	12,044	29,336	23,456
Professional fees	78,449	67,024	153,977	134,023
Other operating expenses	31,082	20,509	48,430	42,858
Restructuring Charges Member
Restructuring Cost And Reserve [Line Items]
Personnel costs	2,866		12,232
Net occupancy expenses	2,660		3,046
Equipment Expense	66		224
Professional fees	315		781
Other operating expenses	267		644
Restructuring Charges Member | Segment, Continuing Operations [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring Charges	$ 6,174	$ 4,574	$ 16,927	$ 4,574