Subsequent Events: (Details) (USD $) In Billions, except Per Share data, unless otherwise specified	3 Months Ended	0 Months Ended	3 Months Ended
	Dec. 31, 2012	Apr. 30, 2013 Subsequent event	Jun. 30, 2013 Subsequent event
Subsequent events:
Workforce rebalancing			$ 1
Dividend declared (in dollars per share)	$ 0.85	$ 0.95
Dividend declared, date		Apr. 30, 2013
Dividend payable, date		Jun. 10, 2013
Shareholders of record, date		May 10, 2013
Dividend per share increase (in dollars per share)		$ 0.10
Dividend per share increase (as a percent)		12.00%
Additional amount authorized under stock repurchase program		$ 5