Stock Options and Restricted Shares - Unvested Restricted Awards (Details) - Restricted stock	6 Months Ended
	Jun. 30, 2017 $ / shares shares
Number
Unvested, beginning of period (in shares)	820,539
Shares awarded (in shares)	233,340
Conversion of previously awarded restricted share units to restricted share awards (in shares)	43,680
Shares assumed in connection with acquisition of BNC (in shares)	136,890
Restrictions lapsed and shares released to associates/directors (in shares)	(212,659)
Shares forfeited (in shares)	(17,765)	[1]
Unvested, end of period (in shares)	1,004,025
Grant Date Weighted-Average Cost
Unvested, beginning of period (in dollars per share) | $ / shares	$ 36.47
Unvested, end of period (in dollars per share) | $ / shares	$ 50.10
Shares forfeited due to failure to meet performance targets (in shares)	0

[1] Represents shares forfeited due to employee termination and/or retirement. No shares were forfeited due to failure to meet performance targets.