Share-Based Compensation: (Details) (USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended
	Sep. 30, 2012
Weighted average exercise price
Outstanding, aggregate intrinsic value	$ 1,821
Exercisable, aggregate intrinsic value	$ 1,362
Stock options
Share-based compensation disclosures
Options cancelled in connection with separation (in shares)	2,900,000
Activity in the entity's stock option plans
Outstanding, beginning of period (in shares)	2,096,000
Granted (in shares)	111,000
Exercised (in shares)	(669,000)
Forfeited and expired (in shares)	(83,000)
Outstanding, end of period (in shares)	1,455,000
Exercisable (in shares)	1,001,000
Weighted average exercise price
Outstanding, weighted average exercise price, beginning of period (in dollars per share)	$ 20.11
Granted, weighted average exercise price (in dollars per share)	$ 23.74
Exercised, weighted average exercise price (in dollars per share)	$ 17.54
Forfeited and expired, weighted average exercise price (in dollars per share)	$ 25.14
Outstanding, weighted average exercise price, end of period (in dollars per share)	$ 21.29
Exercisable, weighted average exercise price (in dollars per share)	$ 21.61
Outstanding, weighted average contractual life	5 years 7 months 6 days
Exercisable, weighted average contractual life	4 years 6 months
2007 Plan | Stock options
Activity in the entity's stock option plans
Outstanding, beginning of period (in shares)	1,329,000
Granted (in shares)	111,000
Exercised (in shares)	(430,000)
Forfeited and expired (in shares)	(5,000)
Outstanding, end of period (in shares)	1,005,000
Exercisable (in shares)	551,000
1998 Plan | Stock options
Activity in the entity's stock option plans
Outstanding, beginning of period (in shares)	572,000
Exercised (in shares)	(190,000)
Forfeited and expired (in shares)	(78,000)
Outstanding, end of period (in shares)	304,000
Exercisable (in shares)	304,000
Predecessor Plan 1998 Directors' Plan
Activity in the entity's stock option plans
Outstanding, beginning of period (in shares)	195,000
Exercised (in shares)	(49,000)
Outstanding, end of period (in shares)	146,000
Exercisable (in shares)	146,000