Share-based compensation (Details)	Mar. 31, 2014	May 11, 2010
Equity and Incentive Plan (EIP)
Share-based compensation
Shares remaining available for future issuance	3,200,000
Shares that can be issued upon vesting of outstanding units and achievement of performance goals	2,900,000
Stock Option and Incentive Plan (SOIP)
Share-based compensation
Shares remaining available for future issuance	1,000	0
Nonemployee Director Stock Plan (2011 Director Plan)
Share-based compensation
Shares remaining available for future issuance	202,460